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  • 101
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2365-2368 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chirale Butadiene, 91) Präparative Anreicherung enantiomerer 2,3,4,5-Tetrabrom-2,4-hexadiene durch Flüssigkeits-ChromatographieDie Enantiomeren des Diols 1 wurden durch Flüssigkeits-Chromatographie an Triacetylcellulose teilweise getrennt (Enantiomere Reinheiten P = 29% und 24%), während die Diether (+)- und (-)-2 mit P = 80% (Tab. 1) erhalten wurden. Ihre Schwellen der Teilrotation um die zentrale Einfachbindung wurden durch thermische Racemisierung gemessen und mit denen entsprechender Tetrachlordiene 3 und 4 verglichen (Tab. 3).
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  • 102
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3378-3384 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Trimethylsilyl-substituted 1,3-Dithietane 1,1,3,3-TetroxidesSubstitution reactions of 1,3-dithietane 1,1,3,3-tetroxide (1) (sulfene dimer) have been regarded as difficult. We now succeeded in the silylation of 1 by the reaction with trimethylsilyl nonafluorobutanesulfonate (2) in the presence of triethylamine yielding 2,4-bis(trimethylsilyl)-(3) and 2,2,4-tris(trimethylsilyl)-1,3-dithietane1,1,3,3-tetroxide (4) as well as - via a metallation - the four times silylated product, which has the structure 1-(tirmethylsiloxy)-2,4,4-tris(trimethylsilyl)-1,3-dithiet-1-ene 1,3,3,-trioxide (5b) and which can be considered as the first enol ether of a sulfone.
    Notes: Substitutionsreaktionen an 1,3-Dithietan-1,1,3,3-tetroxid (1) (Disulfen) galten bisher als schwierig. Es gelang nun die Silylierung von 1 mit Nonafluorbutansulfonsäure-trimethylsilylester (2) in Gegenwart von Triethylamin zu 2,4-Bis(trimethylsilyl)-(3) und 2,2,4-Tris(trimethylsilyl)1,3-dithietan-1,1,3,3-tetroxid (4) bzw. nach Metallierung zum vierfach silylierten Produkt, das als 1-(Trimethylsiloxy)-2,4,4-tris(trimethylsilyl)-1,3-dithiet-1-en-1,3,3-trioxid 5b) vorliegt und als erster Enolether eines Sulfons angesehen wurden kann.
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  • 103
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3385-3394 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Tetra(cyclopropyl)phosphonium cation and the Tri(cyclopropyl)phosphonium CyclopropylideTertiary phosphane can not be quaternized by cyclopropyl halides. The preparation of the three possible mixed cyclopropyl/methyl phosphonium salts [CH3)n(c-C3H5)4 - nP]+X- with n = a - 3 and of the corresponding ylides (CH3)n(c-C3H5)3 - nP = CH2 with n = 0 - 2 (1 - 3) is therefore only accomplished via the cyclopropylphosphanes or through formation o the cyclopropyl ring at the phosphonium center. Quaternization of tri(cyclopropyl)phosphane with 1,3-dibromopropane followed by treatment wih base thus also allows the synthesis of the tri(cyclopropyl)phosphonium cyclopropylide (5). With acids, 5 is converted into tetra(cyclopropyl)phosphonium salts. All three ylides 1 - 3 exist as methylides, and isomerization to cyclopropylides is not observed. 2 and 3 yield ethylphosphonium salts on reaction with methyl iodide. 5 is the only cyclopropylide bearing solely aliphatic substituents. Ist unusal NMR parameters indicate an equilibrium in which the CH protons are involved in a rapid scrambling process among the tautomers. The ylides 1 - 3 and 5 are colourless liquids, thermally stable up to 200°C, and of high chemical reactivity. Reduced reactivity is encountered in the tri(cyclopropyl)phosphonium benzylide (4).
    Notes: Tertiäre Phosphane sind mit Cyclopropylhalogeniden nicht quartärisierbar. Die Darstellung der drei Möglichen (Cyclopropyl/Methyl)Phosphoniumsalze [(CH3)n(c-C3H5)4-nP]+X- mit n = 1 - 3 und der korrespondierenden Ylide (CH3)n(c-C3H5)3-nP = PH2 mit n = 0 - 2 (1 - 3) gelingt daher nur über die Cyclopropylphosphane oder über den Aufbau des Cyclopropylrests am Phosphoniumzentrum. Quartärisierung mit 1,3-Dibrompropan und nachfolgende Cyclisierung mit Basen ermöglicht so auch erstmals die Darstellung von Tri(cyclopropyl)phosphonium-cyclopropylid (5) aus Tri(cyclopropyl)phospan. Mit Säuren entstehen aus 5 Tetra(cyclopropyl)phosphoniumsalze. Die Ylide 1 - 3 liegen alle als Methylide vor und eine Isomerisierung zum cyclopropylid wird nicht beobachtet. Mit Methyliodid entstehen aus 2 und 3 die Ethylphosphoniumsalze. - 5 ist das einzige rein aliphatisch substituierte Cyclopropylid. Seine ungewöhnlichen NMR-Parameter zeigen ein Tautomerengleichgewicht an, bei dem die CH-Protonen einem raschen Austausch unterworfen sind. Die vier Ylide 1 - 3 und 5 sind farblose, bis 200°C thermisch stabile Flüssigkeiten hoher Reaktivität. Nur im Tri(cyclopropyl)phosphonium-benzylid(4) ist die Reaktionsfähigkeit deutlich gemindert.
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  • 104
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3403-3411 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rasche thermische Öffnung und Schließung einer B-N-Bindung in 2-(Aminomethyl)benzolboronaten1)1H-, 11B- und 15N-NMR-Verschiebungen weisen darauf hin, daß die Titelverbindungen 1 - 6 (Tab. 1) eine intramolekulare B - N-Bindung ausbilden, die laut 1H- und 13C-NMR mit hoher Frequenz geöffnet (δ G c≠ = 40 bis 54 kJ/mol, Tab. 2) und wieder geschlossen wird.
    Notes: The Title compounds 1 to 6 (Table 1) are shown by 1H, 11B, and 15N NMR shifts to fom an intramolecular B - N bond which, according to 1N and 13C NMR, is frequently broken (δ G c≠ = 40 to 54 kJ/mol, Table 2) and re-formed.
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  • 105
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3395-3402 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of 2-Amino-3, 7-dihydro-7(β-D-ribofuranosyl)-4H-pyrrolo[2,3-d]pyrimidin-one - 7-Deazaguanosine - the Parent Compound of the Nucleoside Q2-Amino-3, 7-dihydro-7-(β-D-ribofuranosyl)-4H-pyrrolo[2,3-d]pyrimidin-4-one (1a), the parent compound o e rare nucleoside Q, has been synthesized using the pyrrolo [2,3d]pyrimidine derivative 3a11) which was available by phase transfer glycosylation. N-3 alkylation of 3a with chloromethyl isopropyl ether yields 3b, which reacted in a molten mixture of sodium hydride/acetamide to give 3c. Boron trichloride in methylene chloride removes the isopropoxymethyl as well as the benzyl groups at - 78°C simultaneously with formation of 4c. After ammonolysis of 4c 7-deazaguanosine &1par;la) was obtained. IN contrast to guanosine, la shows an anomalous weak Cotton effect implying an unusual flexibility of the nucleobase around the N-glycosylic bond.
    Notes: 2-Amino-3 7,dihydro-7(β-D-ribofuranosyl)4H-pyrrolo[2,3-d]pyrimidin-4-on (1a), die Stammverbindung des seltenen Nucleosids Q, wurde aus dem durch Phasentransferglycosylierung erhaltenen Pyrrolo [2,3-d]pyrimidin-Derivat 3a11) dargestellt. N-3-Alkylierung von 3a durch Chlormethyl-isopropyl-ether führt zu 3b und Austausch der 2-Methylthiogruppe in einer NaH/Acetamid-Schmelze zum geschützten 7-Desazaguanosin 3c. Bortrichlorid im Methylenchlorid entfernt bei - 78°C sowohl den Isopropoxymethylrest als auch die Benzylschutzgruppen unter Bildung von 4c. Nach dessen Ammonolyse erhält man 7-Desazaguanosin (1a), das im Gegensatz zu Guanosin einen anomal schwachen Cotton-Effekt zeigt, der auf starke konformative Beweglichkeit der Nucleobase an der N-glycosylischen Bindung hinweist.
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  • 106
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterocyclic β-Enamino Esters, 27 synthesis of Heterocondensed 6H-1,3-Oxazin-6-ones from N-Acylenamino Esters in the system Triphenylphosphane/Hexachloroethane/TriethylamineA simple ring closure reaction of N-acylenamino esters (1b, e,2,3a-f,7) in the system triphenyl-phosphane/hexachloroethane/triethylamine is described proceeding with high yields. Under chlorinating 3-ester cleavage heterocondensed 6H-1,3-oxazin-6-ones 4a -f, 5, 6b, e, 8, 9 are formed (UV, IR, NMR, MS).
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  • 107
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3197-3208 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: anti-[4+4]-Dicyclopentadiene.The synthesis of anti-tricyclo[4.2.1.12,5]deca-3,7-diene(2) starting from the [4+6]-cycloadduct 4a derived from cyclopentadiene and tropon is described. Compound 2 decomposes at 200°C yielding a Mixture of cyclopentadiene (12), endo-[2+4]-dicyclopentadiene (13), anti-cis-[2+2]-dicyclopentadiene (14) and the cyclopentenyl-cyclopentadienes 15 and 16. The formation of a common diradical intermediate 11 in the decomposition of 2, 13 and 14 has been sought by means of the kinetic analyses of these reactions.
    Notes: Die Synthese des anti-tricyclo[4.2.1.12,5] deca-3,7-diens (2) aus dem [4+6]-Cycloaddukt 4a von Cyclopentadien und Tropon wird beschrieben. Bei Temperaturen um 200°C zerfällt 2 in ein Gemisch aus Cyclopentadien (12), endo-[2+4]-Dicyclopentadien (14) sowie den Cyclopentenyl-cyclopentadienen 15 und 16. Aufgrund der kinetischen Analyse dieser Reaktion sowie der Kinetik der Thermolysen von 13 und 14 wird geprüft, ob bei diesen Reaktionen ein gemeinsames Diradikal 11 durchlaufen wird.
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  • 108
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3209-3219 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition Metal Carbene Complexes, CXVII1) [(Arylseleno)(diethylamino)carbene]pentacarbonylchromium(0)Pentacarbonyl(diethylaminocarbyne)chromium tetrafluoroborate, [CO)5CrCNEt2]BF4, (1) reacts with lithium arylselenolate, LiSeR, (3) [R = 4-C6H4CF3 (a), 4-C6H4Br (b) 4-C6H4F (c), C6H5 (d), 4-C6H4CH3 (e), 4-C6H4OCH3 (f), 1-C10H7 (g)] with addition of the selenolate anion to the carbyne carbon atom to give [(arylseleno)(diethylamino)carbene]pentacarbonylchromium(0), (CO)5Cr[C(SeR)NEt2], (4a - g). The complexes 4 were characterized by elemental analyses, spectroscopic data and in the case fo 4d additionally by an X-ray analysis. On heating in solution, 4a - g rearrange with CO-elimination and C,Cr-migration of SeR to the corresponding trans-(arylseleno)tetracarbonyl(diethylaminocarbyne)chromium complexes, trans-RSe(CO)4-CrCNEt2, (5a - g).
    Notes: Pentacarbonyl(diethylaminocarbin)chrom-tetrafluoroborat, [(CO)5CrCNEt2]BF4, (1) reagiert mit Lithium -arylselenolat, LiSeR, (3) [R = 4-C6H4CF3 (a), 4-C6H4Br (b) 4-C6H4 (c), C6H5 (d), 4-C6H4CH3 (e), 4-C6H4OCH3 (f), 1-C10H7 (g)] unter Addition des Selenolat-Anions an das Carbinkohlenstoffatom und Bildung von [Arylseleno)(diethylamino)carben]pentacarbonylchrom(0), (CO)5Cr[C(SeR)NEt2], (4a-g). Die Komplexe 4 wurden elementaranalytisch, spektroskopisch sowie im Fall von 4d zusätzlich durch eine Röntgenstrukturanalyse gesichert. Beim Erwärmen in Lösung lagern sich 4a-g unter CO-Abspaltung und C, Cr-Wanderung von SeR zu den entsprechenden trans-(Arylseleno)tetracarbonyl(diethylaminocarbin)chrom-Komplexen, trans-RSe(CO)4(CrCNEt2, (5a-g) um.
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  • 109
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3233-3241 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units for Oligosaccharides, XXXIII1) Synthesis of β-Glycosidically Linked Disaccharides of L-RhamnoseThe 2,3,4-tri-O-benzyl-α-L-rhamnopyranosyl bromide (4) is a reactive halogenose which in the presence of a silver silicate catalyst reacts with saccharides containing a reactive hydroxyl group to dive a β-glycosidically linked disaccharide with good selectivity. The three β(1 → 4) and β(1 → 3) linked disaccharides of L-rhamnose 6, 17, and 27 were made in this way with either L-rhamnose or D-galactose as hydroxyl group component. Subsequent deprotection gave the free disaccharides 8, 19 and 31 respectively.
    Notes: Das 2,34-Tri-O-benzyl-α-L-rhamnopyranosylbromid (4) ist eine reaktive Halogenose, die sich bei Gegenwart eines Silbersilicatkatalysators mit Sacchariden, die eine reaktive Hydroxylgruppe enthalten in guter Selektivität zu β-glycosidisch verknüpften Disacchariden umsetzen läßt. Die β(1 → 4)- und β(1 → 3)-verknüpften Disaccharide der L-Rhamnose 6, 17 und 27 mit L-Rhamnose und D-Galactose als Hydroxylkomponenten wurden auf diesem Wege dargestellt. Durch Entblockierung wurden die freien Disaccharide 8, 19 und 31 erhalten.
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  • 110
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3462-3466 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical Calculations of the CO - CO Repulsion Potential in Dinuclear Carbonyl ComplexesThe van der waals repulsion between CO molecules has been obtained by means of quantum mechanical ab initio calculations. The results show in a quantitative way how this interaction between parallel CO ligands on neighbouring metals counteracts bonding forces of single or double bonds between metal atoms.
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  • 111
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3467-3470 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Synthesis of Some Imino Pentafluorosulfanyl DerivativesFrom the reaction of SF5NSCl2 and Ag2O in nitromethane SF5NSO (1) is isolated. The also obtained 2 is probably formed form 1. In the presence of CsF 1 and Cl2 will give SF5NSOCIF (4)
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  • 112
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 113
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3471-3484 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: β,β-Diacyl-enamines and -enoles, 9: Synthesis of Aminomethylene Derivatives of Open-Chain Active Methylene CompoundsThe reaction of a combination of primary or secondary aromatic or aliphatic amines with orthocarboxylic esters upon a variety of open-chain CH2-acidic molecules gives N-substituted aminoalkylidene derivatives. The method is highly recommended for methylene compounds activated by cyano, nitro, or phenylsulfonyl groups, whereas low yields are obtained, when highly enolized active methylene compounds are used. CH2-Acidic carboxylic acids give salts 10a-g.
    Notes: Die Reaktion primärer und sekundärer aromatischer oder aliphatischer Amine mit Orthocarbonsäureestern und offenkettigen CH2-aciden Verbindungen liefert N-substituierten Aminoalkylidenderivate; die Ausbeuten variieren stark mit der Natur der aktivierenden Gruppen. Die Methode kann für solche CH2-acide Moleküle empfohlen werden, welche durch eine nichtenolisierbare Gruppe (CN, NO2 oder PhSO2) aktiviert sind, während niedrige Ausbeute oder keine Umsetzung zu erwarten ist, wenn stark enolisierte methylenaktive Verbindungen eingesetzt werden. CH2-Acide Carbonsäuren liefern die Salze 10a-g.
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  • 114
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3499-3504 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Phosphonium Hydrogendichlorides, II: Three Crystal Structures in ComparisonBy means of crystal structure analysis the compounds [(4-CH3OC6H4)(CH3)PCl2][ClHCl] (1), [(4-CH3OC6H4)PCl3][ClHCl] (2), and [(4-C2H5OC6H4)PCl3][ClHCl] (3) are confirmed as phosphonium hydrogendichlorides and the number of existing geometric parameters of hydrogen bonding between Cl atoms in crystals is substantially increased. The symmetric hydrogendichloride anions who the shortest distances Cl…Cl (312.1 pm in 2) and the largest distance of this kind (328.8 pm also in 2) is observed in the anion with the shortest Cl-H bond.
    Notes: Durch Kristallstrukturanalyse werden die Verbindungen [(4-CH3OC6H4)(CH3)PCl2][ClHCl] (1), [(4-CH3OC6H4)PCl3][ClHCl] (2) und [(4-C2H5OC6H4)PCl3][ClHCl] (3) als Phosphonium-hydrogendichloride bestätigt und die vorhandenen geometrischen Daten zur Wasserstoffbrückenbindung zwischen Cl-Atomen in Kristallen deutlich vermehrt. Die symmetrischen Hydrogendichlorid-Anionen zeigen die kürzesten Abstände Cl…Cl (312.1 pm in 2), und der längste Abstand dieser Art (328.8 pm ebenfalls in 2) wird beim Anion mit der kürzesten Bindung Cl—H beobachtet.
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  • 115
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3485-3498 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Phosphonium Hydrogendichlorides, I Preparation and Properties of Phosphonium HydrogendichloridesPhosphonium hydrogendichlorides of general formula [RR′PCl2]+ [ClHCl]- (1) and [RPCl3]+ [ClHCl]- (5) as well as of the bifunctional type [P(R)Cl2—R′ — P(R)Cl2]2+ 2[ClHCl]- (6) are obtained by differnt methods as well crystallized compounds, which are extremely sensitive toward moisture. Their structures are confirmed by spectroscopic methods and conductivity measurements. - It is shown that the stability of the phosphonium ion is increased by the +M-effect of R, thus favouring the formation of [ClHCl]-. Some reactions of 1 and 5 are described. On loosing HCl, they give the corresponding Phosphoranes RR′PCl3 (3) and RPCl4 (4). This reaction is reversible. By reaction with HBr, 1 and 5 are converted into the bromophosphoranes RR′PBr3 (8) and RPBr4 (9), while phosphonium hydrogendibromides [P(R)Br2—R′—P(R)Br2]2+ 2[BrHBR]- (7) are obtained from 6.
    Notes: Phosphonium-hydrogendichloride der Zusammensetzung [RR′PCl2]+ [ClHCl]- (1) und [RPCl3]+ [ClHCl]- (5) bzw. des bifunktionellen Typs [P(R)Cl2—R′ — P(R)Cl2]2+ 2[ClHCl]- (6) erhält man als extrem hydrolyseempfindliche, gut kristallisierende Stoffe nach verschiedenen Methoden. Ihre Konstitution wird durch spektroskopische Untersuchungen und Leitfähigkeitsmessungen sichergestellt. - Es wird gezeigt, daß der +M-Effekt von R die Stabilität des Phosphonium-Ions erhöht und dadurch die Bildung von [ClHCl]- begünstigt. Einige Reaktionen von 1 und 5 werden beschrieben. So erhält man aus ihnen durch HCl-Entzug die entsprechenden Phosphorane RR′PCl3 (3) und RPCl4 (4). Diese Reaktion ist reversibel. Die Umsetzung mit HBr führt bei 1 und 5 zu den Bromphosphoranen RR′PBr3 (8) und RPBr4 (9), bei 6 hingegen zu Phosphonium-hydrogendibromiden [P(R)Br2—R′ — P(R)Br2]2+ 2[BrHBr]- (7).
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  • 116
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3505-3517 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Generation and Evidence of the Silaethene Me2Si=C(SiMe3)2: Thermolysis of (Me3Si)2(Me2XSi)CLi (X e. g. Hal, OR, SR)Thermal decomposition of Me2Xsi—CLi(SiMe3)2 (1,LiX) in deithyl ether at - 102 to 10°C leads under intramolecular LiX-elimination (X = Hal, TosO, Ph2POn, PhS) to 1,3-disilacyclobutane [Me2Si—C(SiMe3)2]2. (2). The reactive intermediate product is the silaethene Me2Si=C(SiMe3)2 (1) the intermediate formation of which has been established by the determination of reaction rates and order and also through chemical means by trapping 1 with 2, 3-dimethyl-1,3-butadiene. In the last case a [2 + 4]-cycloadduct as well as an ene-reaction product is formed. The speed of intramolecular LiX-elimination from 1,LiX decreases in the order: 1, LiOTos 〉 1,LiCL 〉 1,LiBr 〉 1,Lil 〉 1,Ph2PO4Li 〉 1,LiSPh ≍ 1,LiF 〉 1,Ph2PO2Li.
    Notes: Der thermische Zerfall von Me2XSi—CLi(SiMe3)2 (1,LiX) führt in Diethylether bei -102 bis 10°C unter intramolekularer LiX-Eliminierung (X = Hal, TosO, Ph2POn, PhS) zum 1,3-Disilacyclobutan [Me2Si—C(SiMe3)2]2 (2). Reaktives Zwischenprodukt ist das Silaethen Me2Si=C(SiMe3)2 (1), dessen intermediäre Bildung auf kinetischem Wege durch Bestimmung von Reaktionsordnung und -geschwindigkeit der Eliminierungsreaktion sowie auf chemischem Wege durch Abfangen von 1 mit 2,3-Dimethyl-1,3-butadien wahrscheinlich gemacht werden konnte. In letzterem Falle entsteht ein [2 + 4]-Cycloaddukt sowie ein En-Reaktionsprodukt. Die Geschwindigkeit der intramolekularen LiX-Eliminierung aus 1, LiX nimmt in der Richtung 1,LiOTos 〉 1,LiCL 〉 1,LiBr 〉 1,Lil 〉 1,Ph2PO4Li 〉 1,LiSPh ≍ 1,LiF 〉 1,Ph2PO2Li ab.
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  • 117
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3916-3921 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Small Rings, 34: Attempts to Synthesize DimethyltetrahedraneIrradiation of dimethyltricyclo[2.1.0.02,5]pentanone (2) and 4,6-dimethyl-α-pyrone (6) in solution leads to products which are derivatives of 1,3-dimethylcyclobutadiene (1). However, in an argon matrix photochemical excitation of 2 results in the formation of methylenecyclobutene 12 which is in a photoequilibrium with vinylallene 11. Under analogous conditions pyrone 6 yields photostable 1,3-dimethylcyclobutadiene (1) via the bicyclic form 9. It is possible that dimethyltetrahedrane (14) is an intermediate in the decarbonylation of 2 into 11 ⇌ 12.
    Notes: Bestrahlung von Dimethyltricyclo[2.1.0.02,5]pentanon (2) und 4,6-Dimethyl-α-pyron (6) in Lösung führt zu Produkten, die sich von 1,3-Dimethylcyclobutadien (1) ableiten. In einer Argon-Matrix dagegen entsteht aus 2 bei photochemischer Anregung das mit dem Methylencyclobuten 12 in einem Photogleichgewicht stehende Vinylallen 11. Unter analogen Bedingungen liefert Pyron 6 über die bicyclische Form 9 photostabiles Cyclobutadien 1. Es ist möglich, daß bei der Decarbonylierung von 2 in 11 ⇌ 12 Dimethyltetrahedran (14) als Zwischenprodukt auftritt.
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  • 118
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    Keywords: Chemistry ; Inorganic Chemistry
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    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Small Rings, 33: Attempts to Synthesize DiphenyltetrahedraneCarbene 7, formed on photochemical or thermal excitation of (2,3-diphenyl-2-cyclopropen-1-yl)-diazomethane (6i), splits mostly into two acetylenes 8 und 9 instead of undergoing an intramolecular cycloaddition. Photolysis of the Masamune ketone 16 depending on the reaction conditions gives either p-terphenyl or a mixture of the two cyclooctatetraenes 18 und 19. The intermediate formation of tetrahedrane 10 would fit into the mechanistic picture of this fragmentation.
    Notes: Das bei photochemischer oder thermischer Anregung von (2,3-Diphenyl-2-cyclopropen-1-yl)diazomethan (6i) entstehende Carben 7 geht anstatt einer intramolekularen Cycloaddition bevorzugt eine Fragmentierung in die beiden Acetylene 8 und 9 ein. Bei Belichtung des Masamune- ketons 16 kann abhängig von den Reaktionsbedingungen entweder p-Terphenyl oder ein Gemisch der beiden Cyclooctatetraene 18 und 19 isoliert werden. Die intermediäre Ausbildung des Tetrahedrans 10 fügt sich gut in das mechanistische Bild ein.
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  • 119
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3959-3964 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Small Rings, 37: Further Attempts on Matrix Isolation of TetramethyltetrahedraneIrradiation of diketone 4 or cyclobutenedicarboxylic anhydride 6 in an argon matrix leads to tetramethylcyclopentadienone (5). On the contrary, the valence isomeric anhydride 7 gives cyclobutadiene 3 via lactone 8 which also can be prepared directly from α-pyrone 10. Tetramethyltetrahedrane (2) cannot be detected.
    Notes: Belichtung von Diketon 4 oder Cyclobutendicarbonsäureanhydrid 6 in einer Argonmatrix führt zu Tetramethylcyclopentadienon (5). Im Gegensatz dazu liefert das zu 6 valenzisomere Anhydrid 7 über das bicyclische Lacton 8, welches auch direkt aus dem α-Pyron 10 zugänglich ist, das Cyclobutadien 3. Tetramethyltetrahedran (2) ist nicht nachweisbar.
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  • 120
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2632-2639 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical Ions, 47. Note on the Structural Change during the One-Electron Oxidation of Bis(dimethylamino) DisulfideOn one-electron oxidation, (H3C)2N—S—S—N(CH3)2 considerably changes its structure: where as the neutral molecule according to the ionization band pattern of the PE spectrum displays N and S lone pairs perpendicular to each other, as ESR spectroscopic comparison suggests a planarized skeleton for the radical cation. INDO closed and open shell total energy hypersurfaces for the model compounds H2N—S—S—NH2 and support the discussion of the spectra.
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  • 121
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    Topics: Chemistry and Pharmacology
    Notes: Metal Alkyl and Aryl Compounds, XXVII. Preparation and Crystal structure of Bis(phenylethynyl)bis(N, N, N′,N′-tetramethylethylenediamine)magnesium, Mg(C≡CPh)2(tmeda)2The title compound has been prepared from bis(phenylethynyl)magnesium and N, N, N′,N′-tetramethylethylenediamine (tmeda) and investigated by X-ray diffraction methods (orthorhombic space group Cmcm, Z = 4, 696 (reflections, R = 0.049). It represents a first example of an organomagnesium compound with octahedral coordination of the central atom. The phenylethynyl ligands are in trans position.
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  • 122
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2644-2648 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and Properties of B(OTeF5)3, Cs[B(OTeF5)4], and B(OTeF5)3·CH3CNInteraction of BCl3 with HOTeF5 affords B(OTeF5)3 (1) in quantitative yield. This compound reacts with CsOTeF5 to give Cs[B(OTeF5)4] (2) and with acetonitrile to form the adduct B(OTeF5)3·CH3CN (3). Thermolysis of 1 above 130°C leads to TeOF4 which cannot be isolated, but dimerizes to 4 and polymerizes to F5Te[OTeF4]nOTeF5.
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  • 123
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2649-2652 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Arginine Containing Peptides by Means of the Condensing Reagent Tris(dimethylamino)phosphane/Hexachloroethane/1-HydroxybenzotriazoleThe combination of the title reagents is well suited for building up protected oligopeptides contatining arginine.
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  • 124
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2653-2657 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and Properties of, and Reactions with, Metal-Containing Heterocycles, XVI1) Five-Membered Tungsten-, Iron-, and Nickel-Containing MetallacycloalkanesThe metallacyclopentanes, (3a-c) [m = 1-3: LnM = h5-C5H5Ni (3a), h5-C5H5Fe (3b), h5-C5H5W (3c)] are obtained by reductive cycloelimination of the complexes Ln(OC)m-1M(X)PPh2[CH2]3Cl (2a-c) with sodium amalgam. 3b is also formed from h5-C5H5-(OC)2FeBr (1b) and PPh2[CH2]3MgCl. 3a,b insert SO2 into their M—C σ bond to give the cyclic S-sulfinates (4a,b).
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  • 125
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2947-2955 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: N-Ethyl lyxo Purine Nucleoside CarboxamidesMethyl-2,3-O-isopropylidene lyxuronate (1a) was transformed into 1 α-chloro-1-desoxy-N-ethyl-2,3-O-isopropylidene lyxuronamide (2d). Direct molten state condensation of 2d with silylated 6-chloro- and 2,6-dichloropurine (4a, b) yields mainly N-ethyl-N-9-purinyl nucleoside carboxamides with α and β-configuration (5a, b and 6a, b). The structure of these compounds was established from 1H- and 13C-NMR data.
    Notes: Aus 2,3-O-Isopropylidenlyxuronsäure-methylester (1a) wurde was 1 α-Chlor-1-desoxy-N-ethyl-2,3-O-isopropylidenlyxuronamid (2d) hergestellt. Schmelzkondensation mit silyliertem 6-Chlor- und 2,6-Dichlorpurin (4a, b) lieferte im wesentlichen die N-9-verknüpften α- und β-konfigurierten N-Ethyl-lyxo-purinnucleosidcarboxamide 5a, b und 6a, b. Die Struktur der erhaltenen Nucleoside wurde 1H- und 13C-NMR-spektroskopisch gesichert.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2956-2970 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaction of Acetyl Transition Metal Complexes with Phosphorus Ylides - a Further Example of Halide/Metalate AnalogyThe reaction of the acetyl metal complexes LnM—C(O)CH3 [LnM = C5H5(CO)2Fe, C5H5(CO)3Mo, C5H5(CO)2[P(CH3)3]Mo] with the phosphorus ylides (CH3)3P=CH2, C2H5(CH3)2P=CH2, (C2H5)3P=CHCH3 and (C4H9)3P=CH2 in the ratio 1:2 yields the corresponding acetyl-substituted ylides R3P=CR′C(O)CH3 3a-d (R = CH3, C2H5, n-C4H9; R′ = H, CH3) and phosphonium metalates [R4P][MLn]4a-d, 6a, b via heterolysis of the Fe—C-σ-bond and transylidation. With CH3C(O)Cl an analogous way of reaction is observed, which however can be repeated to give the diacetyl ylides R3P=C(COCH3)2 8a, b (R = Ch3, n-C4H9). The new compounds are characterized by spectroscopic methods (NMR, IR) and further reactions.
    Notes: Die Umsetzung der Acetyl-Metallkomplexe LnM—C(O)CH3 [LnM = C5H5(CO)2Fe, C5H5(CO)3Mo, C5H5(CO)2[P(CH3)3]Mo] mit den Phosphor-Yliden (CH3)3P=CH2, C2H5(CH3)2P=CH2, (C2H5)3P=CHCH3 und (C4H9)3P=CH2 im Verhältnis 1 : 2 liefert unter Heterolyse der Fe—C-σ-Bindung und Umylidierung die entsprechenden Acetyl-Ylide R3P=CR′C(O)CH3 3a-d (R = CH3, C2H5, n-C4H9; R′ = H, CH3) und Phosphonium-metallate [R4P][MLn] 4a-d, 6a, b. Mit CH3C(O)Cl wird ein analoger Reaktionsverlauf nachgewiesen, der sich aber wiederholen und zu Diacetyl-Yliden R3P=C(COCH3)2 8a, b (R = CH3, n-C4H9) führen kann. Die neuen Verbindungen werden spektroskopisch (NMR, IR) und durch Folgereaktionen charakterisiert.
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  • 127
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 2971-2978 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Reactions of Cationic Chlorobis(phosphane)platinum(II) Complexes[(R3P)2Pt(Cl)H2O]+BF-4 (1) and (R3P)2Pt(Cl)OSO2CF3 (2) have been prepared by abstraction of chloride from cis-(R3P)2PtCl2 using tetrafluoroboric acid or trifluoromethanesulfonic acid, respectively. The protons of the aqua ligand in 1 form hydrogen bridges to the BF-4 anion. The acidic complexes 1 and 2 are useful starting materials for new platinum(II) complexes. HCO-3 neutralizes 1 to form the carbonato complex (Et3P)2PtO2CO (5). The heterogenous reaction of 2a with glycinate gives the cationic chelate complex (6). The coordinated water of 1 is easily substituted by other ligands, e. g. phosphanes. The chloro-bridged complexes [(R3P)2PtCl2Pt(PR3)2]2+ are formed by treatment of 1 or 2 with ethers.
    Notes: [(R3P)2Pt(Cl)H2O]+BF-4 (1) und (R3P)2Pt(Cl)OSO2CF3 (2) (R = Et, n-Bu, Ph; 2 PR3 = Ph2PCH2CH2PPh2) werden durch Chlorid-Abstraktion aus cis-(R3P)2PtCl2 mit Tetrafluoroborsäure bzw. Trifluormethansulfonsäure erhalten. Die Protonen des Aqua-Liganden von 1 bilden Wasserstoffbrücken zum BF-4-Anion aus. Die sauren Komplexe 1 und 2 lassen sich zur gezielten Synthese neuer Platin(II)-Komplexe nutzen. In heterogener Reaktion entsteht aus 2a mit Glycinat der kationische Chelatkomplex (6). Hydrogencarbonat neutralisiert 1 unter Bildung des Carbonatokomplexes (Et3P)2PtO2CO (5). Das koordinierte H2O in 1 läßt sich leicht durch andere Liganden, z. B. Phosphane, ersetzen. 1 und 2 bilden in Ethern die Chloro-verbrückten Dikationen [R3P)2PtCl2Pt(PR3)2]2+.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3056-3062 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal-Boron Compounds, 13. Synthesis and Reactivity of some (Trimethylstannyl)boranes2)The preparation of some amino(trimethylstannyl)boranes and their chemical properties are described. With Me3SnLi (Me = CH3) as a reagent only the synthesis of Me3SnB(NR2)2 (1a, b), Me3SnBCl(NR2) (2a, b), and (Me3Sn)2BNR2 (3b) was achieved. The stannylboranes Me3SnB(NR2)2 show astonishing thermal stability. Their Sn—B bonds are broken by hydrogen, the halogens, and chalcogens as well as by alcohols. HCl cleaves the B—N bond.
    Notes: Die Darstellung einiger Amino(trimethylstannyl)borane und deren chemische Eigenschaften werden beschrieben. Mit Me3SnBCl(NR2) (1a, b) und Me3SnBCl(NR2) )2a, b) (Me3Sn)2BNR2 (3b). Die Stannylborane Me3SnB(NR2)2 sind thermisch erstaunlich stabil. Ihre Sn—B-Bindungen werden von Wasserstoff, den Halogenen, Chalcogenen und Alkoholen gespalten, während HCl die B—N-Bindung öffnet.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3019-3023 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Radicals by Oxidation of λ3-Phosphorin DerivativesThe first ESR spectra, which are observed when 2,4,6-trisubstituted λ3-phosphorins 1a-c are oxidized electrolytically or with dichlorodicyanoquinone (DDQ) in dichloromethane or tetracyanoethene (TCNE) in 1,2-dimethoxyethane, are not - as formerly supposed - those of λ3-phosphorin cation radicals 2a-c. They are secondary radicals of the λ4-phosphorin-type 3 which are produced from the very short living radicals 2 by addition of water from the solvent. Oxidation of 1c in dichloromethane/methanol with DDQ affords the 2,4,6-tri-tert-butyl-1-methoxy-λ4-phosphorin radical 3′c. Further oxidation of the radicals 3 produces the very stable radicals 7a-c, once again by addition of water and deprotonation. Their ESR spectra are very similar to those of the „neutral radicals“, described in the precedent paper, which are formed by the electrolytic oxidation of 1,1-dimethoxy-λ5-phosphorins in dichloromethane in the presence of lithium bromide or by oxidation with lead tetrabenzoate and which are the methyl esters of 7.
    Notes: Die ersten ESR-Spektren, die man bei der elektrolytischen Oxidation von 2,4,6-trisubstituierten λ3-Phosphorinen 1a-c, der Oxidation mit Dichlordicyanchinon (DDQ) in Dichlormethan oder der mit Tetracyanethen (TCNE) in 1,2-Dimethoxyethan beobachtet, sind nicht, wie früher angenommen, die der λ3-Phosphorin-Kationradikale 2a-c. Es sind die von Folgeradikalen vom λ4-Phosphorintyp 3, die aus den sehr kurzlebigen Radikalen 2 durch Addition von Wasser aus dem Lösungsmittel entstehen. Methanolzusatz zum Dichlormethan bei der Oxidation von 1c mit DDQ führt zum 2,4,6-Tri-tert-butyl-1-methoxy-λ4-phosphorin-Radikal 3′c. Bei weiterer Oxidation der Radikale 3 entstehen unter erneuter Addition von Wasser und Deprotonierung die sehr beständigen Radikale 7a-c. Ihre ESR-Spektren unterscheiden sich nur wenig von denen der in der vorstehenden Mitteilung beschriebenen „Neutralradikale“, die bei der elektrolytischen Oxidation aus 1,1-Dimethoxy-λ5-phosphorinen in Dichlormethan bei Anwesenheit von Lithiumbromid oder der Oxidation mit Bleitetrabenzoat entstehen und die den Methylestern von 7 entsprechen.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3044-3055 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Boron, 120. Tetraorganyldiboranes(4): Preparation and Stabilitytert-Butylation of B2(OCH3)4 by LiC(CH3)3 proceeds via [(CH3)3C](CH3O)B—B(OCH3)[C(CH3)3] (1) to give tri-tert-butylmethoxydiborane(4) (2). Tetraalkylation of B2(OCH3)4 is achieved by isopropyllithium; no reaction intermediates were found in this case. Al(C2H5)3 reacts with B2(OCH3)4 to give B2(C2H5)4 which is stable only below - 30°C. On the other hand the CH3O group in 2 is replacable by CH3, and the CH3O groups in 1 by ethyl groups. Thus, product control by steric factors is evident. - The thermal stability of tetraorganyldiboranes(4) is controlled by the steric screening of the boron atoms: tetraisopropyldiborane(4) decomposes slowly at room temperature, tetraethyldiborane(4) rapidly at - 20°C.
    Notes: Die tert-Butylierung von B2(OCH3)4 mit LiC(CH3)3 führt über die Stufe [(CH3)3C](CH3O)B—B-(OCH3)[C(CH3)3] (1) zu Tri-tert-butylmethoxydiboran(4) (2). Die Tetraalkylierung von B2(OCH3)4 gelingt mit Isopropyllithium; Isopropylmethoxydiboran(4)-Zwischenstufen sind nicht faßbar. Al(C2H5)3 reagiert mit B2(OCH3)4 zu dem nur unterhalb von - 30°C stabilen B2(C2H5)4. Die CH3O-Gruppe in 2 ist gegen eine CH3-Gruppe ersetzbar, die CH3O-Gruppen von 1 gegen Ethylgruppen. Produktkontrolle erfolgt somit durch sterische Effekte. - Die thermische Stabilität der Tetraorganyldiborane(4) wird von der sterischen Abschirmung der Boratome gesteuert: Tetraisopropyldiboran(4) zersetzt sich langsam bei Raumtemperatur, Tetraethyldiboran(4) rasch bei - 20°C.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3024-3043 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Boron, 119. Synthesis and Structure of Tris[bis(organylthio)boryl]aminesNMR data of Tris[bis(organylthio)boryl]amines, N[B(SR)2]3, prepared by two different routes, indicate chemically equivalent RS groups in solution. The rather weak screening at boron and nitrogen agrees with the competition of three boron atoms for the lone pair of electrons at nitrogen, e.g. weak BN-π-bonding. - The equivalence of the RS groups is lost in the solid state. One(RS)2B group in each of the compounds 1-4 is strongly twisted against the B3N plane, and following the series 1, 2, 4, and 3 the other two orient themselves more and more coplanarily to this plane. Accordingly, a relatively long BN bond (147-148 pm) is observed besides two shorter BN bonds (143-145 pm) in each of these compounds. This is experimental evidence for the dependence of the B—N distance from π-bond order and its angular dependence. In addition, the structures of the 1,3,2-dithiaborolan, the 1,3,2-benzodithiaborol, and the 1,3,2-dithiaborolene ring systems have been ascertained. Only the latter two posses planar rings. - Mass spectrometric fragmentation of the tris[bis(organylthio)boryl]amines proceeds with preferential retention of BN bonding. For instance, the molecular ion of 2 breaks apart by three successive eliminations of ethylene with formation of the radical cation of NB3S6+ (12), derived from a hitherto unknown tricyclic system.
    Notes: Tris[bis(organylthio)boryl]amine, N[B(SR)2]3, nach zwei verschiedenen Verfahren dargestellt, besitzen in Lösung nach NMR-Untersuchungen chemisch äquivalente RS-Gruppen. Die gefundene geringe Abschirmung des Bors und Stickstoffs steht in Übereinstimmung mit der Konkurrenz von drei Boratomen um das freie Elektronenpaar am Stickstoff, d. h. schwacher BN-π-Bindung. - Im festen Zustand der Verbindungen 1-4 ist dagegen jeweils eine der drei (RS)2B-Gruppen stark gegen die B3N-Ebene verdrillt, und in der Reihe 1, 2, 4 und 3 zunehmend stellen sich die beiden anderen koplanar zu dieser Ebene ein. Dementsprechend beobachtet man eine relativ lange (147-148 pm) neben zwei kürzeren BN-Bindungen (143-145 pm). Dies ist ein experimenteller Beleg für die Abhängigkeit des B—N-Abstands von der π-Bindungsordnung zwischen B und N und ihrer Winkelabhängigkeit. Zugleich wurde die Struktur des 1,3,2-Dithiaborolan-, des 1,3,2-Benzodithiaborol- und des 1,3,2-Dithiaborolen-Ringes ermittelt. Nur die beiden letztgenannten Heterocyclen besitzen ein planares Ringgerüst. Die massenspektrometrische Fragmentierung der Tris[bis(organylthio)boryl]amine verläuft bevorzugt unter Erhaltung der BN-Bindungen. Dabei zerfällt das Molekül-Ion von 2 vor allem unter sukzessiver Abspaltung von 3 mol Ethylen und Bildung des Radikal-Kations NB3S6+ (12), das sich von einem bisher unbekannten Tricyclus ableitet.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3102-3114 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units for Oligosaccharides, XXX. New Efficient β-Glycoside Synthesis of Mannose Glycosides Syntheses of Mannose Containing OligosaccharidesA new method was developed for the stereo selective synthesis of oligosaccharides containing a β-linked mannose-unit which were hitherto not available by direct synthesis. The glycoside synthesis is promoted by a silversilicate-catalyst which was precipitated on aluminium oxide. The trisaccharides 20 and 31 (see german summary) and the tetrasaccharide 33 were synthesized, demonstrating the advantages offered by block synthesis.
    Notes: Es wird eine neue Methode zur selektiven Synthese von Oligosacchariden mit β-verknüpfter Mannose-Einheit entwickelt, für deren direkte Gewinnung es bisher kein Verfahren gab. Als Katalysator dient ein auf Al2O3 niedergeschlagenes Silbersilicat. Es werden die Trisaccharide β-D-Man-(1→4)α-D-Gal-(1→4)-L-Rha (20) und sowie das Tetrasaccharid 33 synthetisiert. Hierbei werden die Vorteile der Blocksynthese demonstriert.
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    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3063-3069 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A Cyclic Carbodiphosphorane and an Open-chain Reference CompoundThe cyclic carbodiphosphorane 8 is prepared from bis(diphenylphosphino)methane (1) and 1,3-dibromopropane, via a diphosphonium salt 6 and a semiquaternary salt 7, through transylidation with salt-free trimethyl methylene phosphorane. The structure is established by 1H-, 13C-, 31P-NMR and mass spectrometry, as well as by X-ray diffraction. Reprotonation with anhydrous HCl regenerates the diphosphonium salt 6. With tetrahydrofuran-borane, 8 is converted into a 1:1-borane complex 9, with the BH3 acceptor attached to the double-ylide carbon bridge. Methylation with CH3I occurs in the same position (10). 1:1-complexes (11, 12) are also formed with dimethylzink and -cadmium. The products are probably dimeric and show a rapid CH3-exchange in solution. - The already known open-chain analogue CH3(C6H5)2P=C=P(C6H5)2CH3 (4) resembles 8 in many respects, including the molecular structure. In the coordination interaction with metals a metalation in the CH3-groups in strongly favoured, however, as it is again shown in the nickel complex 5.
    Notes: Aus Bis(diphenylphosphino)methan (1) und 1,3-Dibrompropan wird über ein Diphosphoniumsalz 6 und ein Semiquartärsalz 7 durch Umylidierung mit salzfreiem Trimethylmethylenphosphoran das cyclische Carbodiphosphoran 8 dargestellt. Der Strukturbeweis gelingt über 1H-, 13C-, 31P-NMR-und Massenspektrum sowie durch eine Röntgenbeugungsanalyse. Durch wasserfreien Chlorwasserstoff wird das Diphosphoniumsalz 6 zurückgebildet. Mit Tetrahydrofuran-Boran wird ein 1:1-Komplex 9 erhalten, der den BH3-Akzeptor am Doppelylid-Brückenkohlenstoffatom gebunden hat. In gleicher Position erfolgt die Methylierung mit Methyliodid (10). Mit Dimethylzink und -cadmium entstehen 1:1-Komplexe (11, 12) vermutlich dimerer Struktur, die in Lösung raschen CH3-Austausch zeigen. - Das schon bekannte offenkettige Analogon CH3(C6H5)2P=C=P(C6H5)2CH3 (4) gleicht in vielen Eigenschaften, einschließlich seiner Molekülstruktur, dem Heterocyclus 8 Bei der Komplexbildung mit Metallen erfolgt hier jedoch bevorzugt Eintritt in die CH3-Gruppen. Der Nickelkomplex 5 ist dafür ein charakteristisches Beispiel.
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    AIChE Journal 27 (1981), S. 13-20 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A suboptimal control algorithm is derived for a continuous latex reactor subject to deterministic and stochastic disturbances to control the pathological behavior of the reactor. An extended Kalman filter based on an instantaneous local linearization technique is used to estimate the reactor states, and a quadratic performance index is used to derive the suboptimal feedback control law. This study successfully demonstrates the application of the multivariable control theory to the control of a simulated continuous latex reactor operating under limit-cycle conditions. The mathematical model used for the control studies was previously developed and has been shown to describe the performance of an actual reactor system extremely well over its entire range of operation.
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    AIChE Journal 27 (1981), S. 33-40 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Infinite dilution activity coefficients (γ∞) in binary liquid mixtures are data of wide practical and theoretical applicability, but their extensive use has been hindered by the experimental limitations of classical vapor-liquid equilibrium techniques. Two new experimental methods for accurate γ∞ determinations are presented. These techniques, both faster and more accurate than classical methods, are complementary, and their applicability to different types of binary systems is discussed.
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    AIChE Journal 27 (1981), S. 59-65 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kerosine or propane was injected near the base of a small, air-fluidized bed of sand at 940°C. The fraction of fuel burnt within the bed was determined from a heat balance, for various particle sizes, fluidizing velocities, and bed depths.Assuming the initial formation of a train of fuel vapor bubbles, theoretical analysis indicated two stages of combustion: (1) rapid consumption of the oxygen initially between fuel vapor bubbles; (2) slow consumption of oxygen initially outside the fuel vapor region by radial diffusion of oxygen and fuel vapor, analogous to a diffusion flame.Comparison of experiment with theory gave effective radial diffusion coefficients of the same order of magnitude as the molecular diffusion coefficient. It was inferred that combustion occurs largely by a diffusion flame within the bed, with diffusion through the particulate phase being the rate-controlling step. This explains why fuel distribution is so important in attaining efficient combustion.
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  • 137
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The gas chromatography technique was applied to measurements of diffusion of n-butane in zeolite NaY. The linear chromatography theory failed to explain these results quantitatively, and a significant system nonlinearity was demonstrated. This nonlinearity is likely associated with non-Fickian diffusion. Order of magnitude estimates of the diffusivity could still be obtained, however. Over the range of temperatures 105 to 240°C, the n-butane diffusivities were in the range 10-8 to 10-6 cm2/s. Similar results were obtained with n-hexane and calculated diffusivities were about an order of magnitude smaller than the corresponding n-butane values. In contrast, limited experiments with cyclohexane, 2, 2-dimethylbutane, and trans-decalin were entirely consistent with the linear chromatography theory. At the measurement temperatures, the intracrystalline diffusion was too rapid to be detected in any of these systems. Attempts to operate at lower temperatures where diffusion might be significant were frustrated by extensive peak broadening and concomitant loss of detector response.
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    AIChE Journal 27 (1981), S. 125-131 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alteration in concentration-independent catalyst decay rates due to the presence of finite external and internal mass transfer resistances is examined. Analytical expressions for external and overall time-dependent catalytic effectiveness are developed. Analysis of diffusion-limited catalyst deactivation in flow reactors is discussed.
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    AIChE Journal 27 (1981), S. 138-148 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A correlation is developed for the solubility of hydrogen in hydrocarbon solvents at temperatures from 310 to 700 K and pressures to 30 MPa (300 bar). The fugacity of dissolved hydrogen at zero pressure is correlated as a function of solubility parameter and temperature. The high-pressure fugacity is obtained upon applying a Poynting factor for which the required partial molal volume of hydrogen is also correlated in terms of solubility parameter and temperature. The Henry constant of hydrogen is included in the correlation. The correlated results are compared with experimental data for 22 systems of binary and ternary solutions and five narrow-boiling cuts of coal liquids. The overall average absolute deviation for all systems studied is approximately 6%.
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    AIChE Journal 27 (1981), S. 120-125 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The interrelation between internal diffusion and concentration-independent deactivation is examined using a simple mathematical model. Analytical procedures are developed for evaluating the performance of single catalyst particles in the presence of diffusion and deactivation. By incorporating time-dependent effectiveness factors in design equations, reactor performance under the combined influence of diffusion and deactivation is predicted. By analogy to the effectiveness factor for non-deactivating systems, the concept of a deactivation effectiveness factor is introduced.
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    AIChE Journal 27 (1981), S. 159-162 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 163-166 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 170-172 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 174-174 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 203-207 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new static cell for vapor-liquid equilibria up to 100 MPa between 233 and 433 K is presented. A detachable sampling microcell and a special chromatographic injector are used in a new sampling system suitable for gas chromatographic analysis of mixtures with high boiling components. The test system is N2 - n-Heptane at 305.45 K.
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    AIChE Journal 27 (1981), S. 193-202 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust particles originally generated by two steelmaking processes were dispersed in an air stream and passed through a pilot-scale high gradient magnetic filter. In accordance with theoretical predictions, the experimental results showed that collection was improved by increasing the depth or density of the steel wool filter, increasing the applied magnetic field, or decreasing the filtration velocity. Collection efficiency increased with particle size up to about 2 μm, above which the efficiency tapered off, apparently due to reentrainment effects. Collection efficiencies of greater than 99% were obtained, indicating that high gradient magnetic filtration may be a practical method of controlling particulate emission from processes in the iron and steel industry.
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    AIChE Journal 27 (1981), S. 284-292 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The existence of multiple stable and unstable steady states in a continuous stirred tank biological reactor (CSTBR) was demonstrated experimentally for the first time. These experiments resulted in the determination of growth rate, yield and intermediate metabolite concentration data entirely from continuous culture. This information was used to qualitatively interpret the stability behavior in terms of the biochemistry and bioenergetics of substrate metabolism.
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    AIChE Journal 27 (1981), S. 301-303 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 316-316 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981) 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 372-377 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents numerical solutions to the nonlinear, coupled boundary-layer equations governing laminar condensation heat and mass transfer in the vicinity of the forward stagnation point of a spherical cold water droplet translating in a saturated mixture of three components. The environment surrounding the droplet is composed of a condensable (steam), a noncondensable and nonabsorbable (air), and a third component which is noncondensable but absorbable (Elemental Iodine, for example). The dispersed and the continuous phases have been treated simultaneously. Results obtained here show excellent agreement with experimental results where available. An important conclusion is that for laminar condensation on a freely falling droplet, for a given thermal driving force and noncondensable gas concentration in the bulk, the dimensionless heat transfer decreases with increasing saturation temperature of the outside medium.
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    AIChE Journal 27 (1981), S. 396-403 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simultaneous biological and activated-carbon treatment of organic wastewaters appears promising. The effects of bacterial film growth on adsorbent particles is investigated by laboratory work and mathematical modelling. Regeneration of the adsorbent due to film growth does occur, but faster than predicted. The discrepancy reflects uncertainty about the structure of bacterial films.
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    AIChE Journal 27 (1981), S. 429-442 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of processes requires the consideration of a wide variety of reactions which are required to transform raw materials into desired products, solve separation problems, and heat or cool process streams. These reactions have to be evaluated on the basis of raw material costs, kinetics, potential separation difficulties, catalyst costs, safety and reliability, as well as other factors that would arise in their industrial implementation. In this paper, the current status of research in reaction path synthesis has been reviewed. Details have been presented on the REACT program that has been developed for the synthesis of reaction paths for industrial organic chemicals.
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    AIChE Journal 27 (1981), S. 277-284 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A calculational method is proposed for the simulation of steady-state, multisolute, countercurrent extraction with axial dispersion. The method provides for complex chemical-equilibrium and phase-equilibrium relationships, and accounts for the individual resistances of the liquid phases in the calculation of mass-transfer rates. The solution procedure follows that developed by Newman (1967, 1968) for systems of simultaneous, second-order difference equations.Three example problems are solved to demonstrate the efficiency and flexibility of the method. These include (1) an example from McSwain and Durbin (1966), (2) calculation of axial-dispersion and mass-transfer parameters from experimental data for the extraction of acetic acid from water by a tertiary amine in an RDC extractor, and (3) simultaneous extraction of solutes that interact in an acid-base complexing reaction at the liquid-liquid interface. The examples all assume that extraction is governed by interphase mass-transfer rates and cell-wise backmixing; however, the method is also applicable to equilibrium-stage separators, separators described by the diffusional model of axial dispersion, and other countercurrent separation processes.
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    AIChE Journal 27 (1981), S. 312-315 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 588-592 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Quantitative measurements of the effect of a third phase of buoyant solid particles on the settling rates of suspensions of heavy particles are reported. It is found that for a wide range of concentration of both buoyant and heavy particles, the settling rates of both solid phases are greatly increased. If the phases are dilute, the settling velocities of both are retarded. The total settling time of heavy particles can be halved, but only under conditions that the light phase is unaccelerated. This suggests that small gas bubbles would form a more satisfactory buoyant phase. The high concentrations of thickened suspensions which result from the acceleration process are also reported.
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    AIChE Journal 27 (1981), S. 632-636 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 673-679 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A procedure for inserting vapor pressure data in the equations of state is presented. It provides a straightforward scheme for the extension of direct methods to the study of phase equilibria of polar mixtures and of solutions containing nonvolatile electrolytes. Some examples of application are also given.
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    AIChE Journal 27 (1981), S. 861-863 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental data and theory both support the contention that there is a maximum solubility in solid-fluid equilibria. An example system, naphthalene-ethylene, at temperatures between the upper and lower critical end points and at pressures from 1 to 1000 bar is considered. There is also a solubility minimum in this system.
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    AIChE Journal 27 (1981), S. 829-836 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general analysis of a cascade of identical recycle units is presented by means of studying the fluid history inside the system. This is an extension of Part I (Mann et al., 1979) in which a single recycle unit was analyzed. The history of a fluid element is expressed in terms of the number of cycles it completes, the time it resides in the system and the total time it resides in a specific section of the system - all are random variables. Concepts from probability theory and stochastic processes are used to derive the number of cycles distribution (NCD), residence time distribution (RTD) and various total regional residence time distributions (TRRTDs) as well as their means and variances. Expressions for the joint distributions of pairs of these random variables are also derived as well as explicit expressions for their covariances and correlation coefficients. Two applications of the results are illustrated: one in analyzing a continuous spouted-bed coating unit and the second in using the cascade as a flexible, physically based multi-parameter flow model.
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    AIChE Journal 27 (1981), S. 928-937 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Isotherm Migration Method of numerically analyzing conduction with phase change is modified to handle surface and external resistances, appearance, and propagation of successive fronts into slabs of composite material of one or more constituents finely dispersed in a matrix, different components transforming at different temperatures. Procedures are developed for selecting temperature intervals between isotherms, initially locating isotherms by means of analytical approximations to the earliest stages, and thereafter inserting and removing isotherms as appropriate, particularly when each component gives rise to a separate front.
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    AIChE Journal 27 (1981), S. 968-974 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An improved model and solution procedure for nonequilibrium, multicomponent, two-phase, steady-state mass transfer problems are developed. Processes as diverse as packed column operation and the drying of porous solids are included. Ideas such as “HETP,” “HTU” or “mass transfer section” are avoided. “Stiff” systems appear to be handled well.
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    AIChE Journal 27 (1981), S. 1002-1008 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Our purpose is to give the physical conditions under which transfer of a surfactant through a fluid interface between two immiscible liquids may induce aperiodic convective motion.Adsorption-desorption rates are considered together with diffusional exchanges. New kinds of surface instabilities are then predicted.
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    AIChE Journal 27 (1981), S. 1017-1020 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 1026-1028 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 1039-1041 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 509-514 
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    AIChE Journal 27 (1981), S. 521-523 
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    AIChE Journal 27 (1981), S. 527-528 
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    AIChE Journal 27 (1981), S. 526-526 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 529-545 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The increasing demands for oil, water, and food produced in an environmentally sound manner have placed emphasis on the manner of their production, a major part of which is concerned with flow through porous media.The movement of materials through porous media is of interest in many disciplines: in chemical engineering - adsorption, chromatography, filtration, flow in packed columns, ion exchange, reactor-engineering; in petroleum engineering - displacement of oil with gas, water and miscible solvents including surface-active agent solutions and description of reservoirs; in hydrology - movement of trace pollutants in water systems, recovery of water for drinking and irrigation, salt water encorachment into fresh water reservoirs; in soil physics - movement of water, nutrients, and pollutants into plants; in biophysics - life processes such as flow in the lung and the kidney.This paper reviews the fundamentals of steady flow through porous media: it discusses the pseudotransport coefficients permeability, capillary pressure, and dispersion and relates these coefficients to the geometry of porous media. It also discusses single-fluid flow, multifluid immiscible flow, and multifluid miscible flow including the effects of heterogeneity, nonuniformity, and anisotropy of media.
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    AIChE Journal 27 (1981), S. 578-587 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper deals with the problem of finding, among many alternatives, the sequence of separation units that will isolate desired products from given feed at the minimum cost. Multicomponent products can be specified. An evolutionary procedure is presented. This method consists of two phases. In the first phase, a good initial structure is created by heuristic methods. In the second phase, the initial structure is successively modified by making evolutionary structural changes. This logic has been programmed on a digital computer and has been tested on several problems.
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    AIChE Journal 27 (1981), S. 605-613 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previously published data for the six binary combinations that can be formed from CO2, H2S, N2 and methanol are used to obtain parameters of the four-suffix Margules equation describing liquid solution behavior. The vapor phase is described by the Soave modification of the Redlich-Kwong equation of state. Isothermal binary data are fit well by these equations. The effects of temperature on the Margules parameters are significant and, except for N2-containing mixtures, the parameters were taken to be inversely proportional to absolute temperature.Experimental data were obtained for multicomponent mixtures of CO2, H2S, N2 and methanol. Model predictions were tested against these data. Comparisons of predicted and measured values of bubble point pressure and equilibrium vapor compositions are satisfactory.
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    AIChE Journal 27 (1981), S. 613-619 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The objective of this paper is to point out the relationship between the relative gain array (RGA) and control system stability and design. Rigorous stability limits are presented for a general 2 × 2 system for several cases involving both steady state and dynamic interactions. These stability limits explicity involve the RGA. Two specific examples of interaction in distillation models are also discussed.
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    AIChE Journal 27 (1981), S. 637-645 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 654-663 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical model is presented to describe the kinetics of nonisothermal sorption for a system in which the main resistance to mass transfer is the macrodiffusional resistance of the absorbent particle bed while the main resistance to heat transfer is the resistance at the external surface of the adsorbent sample. The model is used to interpret experimental kinetic data for the sorption of several hydrocarbons in 10X and 13X zeolite crystals. By varying the configuration of the sample bed and the size of the zeolite crystals it is shown that, for n-heptane and iso-octane in 13X, the intracrystalline diffusional resistance is negligible even in 40-μm crystals. The assumption of intracrystalline diffusion control which has been made in earlier kinetic studies of similar systems is therefore incorrect.
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    AIChE Journal 27 (1981), S. 690-693 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general theory for examining the dynamic as well as static interactions among inputs and outputs in a multivariable control system has been developed. Both state space and frequency domain approaches are used, and at steady state the interaction equations assume the same form as the relative gain array developed by Bristol. Implications of selecting input-output pairings with regard to steady state vs. dynamic consideration are discussed. The application of the method of analysis to a distillation column control system is presented.
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    AIChE Journal 27 (1981), S. 697-699 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981) 
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    AIChE Journal 27 (1981), S. 733-739 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model and iterative correction algorithm are described for the exact solution of separation systems which contain interlinked columns in which some stages have two liquid phases and others have a vapor and liquid phase. The correction algorithm is based on Newton's method and provides for simultaneous correction of all iteration variables. The derivatives are calculated analytically from the model equations. The separation of a binary mixture which forms a heterogeneous azeotrope is analyzed. Modifications to the correction algorithm which provide for fixed condenser temperature and fixed product flows are described. The separation of butanol and water is used to illustrate the method.
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    AIChE Journal 27 (1981), S. 761-767 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the esterification of n-butyl alcohol with acetic acid has been studied experimentally in concentrated solutions at near ambient temperature in the presence of a sulphuric acid catalyst and the rate constants for the forward and reverse reaction determined.The rate data obtained from the homogeneous system has been applied to analyse the performance of a batch-extractive reactor using n-heptane as solvent. The rate of mass transfer of the ester was found to be significant and when introduced in a model of the reaction process gave good agreement with the experimental results.
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    AIChE Journal 27 (1981), S. 793-805 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper deals with defining the relation between modeling of process units and controller design. In the process industries, it is often difficult to obtain accurate process models. It is shown that advanced algorithms such as dead-time compensators require more detailed process information for design than do with PI and PID controllers. A method is described to systematically evaluate the relation between process identification and controller design, stability, and performance. It is shown that conventional gain and phase margins do not provide proper safety margins for dead-time compensators and optimal controllers. Methods for safe design of dead-time compensators are derived, and the approach could be useful in a wide class of problems.To illustrate the approach presented, the design of PI controllers by conventional methods is analyzed. The conditions, as well as the exceptions, are specified in which methods such as described by Ziegler and Nichols or Cohen and Coon will give good results. It is shown that for any stable nonlinear system with an input/output function y = G*p(u), a linearized design function G′pd can be constructed and identified that guarantees stability and reasonable performance of the controller (Eqs. 21 and 22 and Figures 4-7) over a wide range of operating conditions. A rigorous framework for identifying the exceptions and understanding the reason why such methods work is presented.
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    AIChE Journal 27 (1981), S. 819-823 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrochemical measurements of overall mass transfer rates from a single sphere have been performed in a highly turbulent liquid. The increase in mass transfer rate due to turbulence has been shown to be more important at high Reynolds number and high turbulence intensity. Various equations of correlation have been proposed between the overall Sherwood number, the Reynolds number and turbulence intensity, the simplest one being \documentclass{article}\pagestyle{empty}\begin{document}$$ Sh = 6.82\,{\mathop{Re}\nolimits} ^{0.559}\, Tu^{0.069} $$\end{document} A correct agreement has been found with previous heat or mass transfer results between a gas and a sphere.
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    AIChE Journal 27 (1981), S. 851-853 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 27 (1981), S. 853-856 
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    AIChE Journal 27 (1981), S. 864-866 
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    AIChE Journal 27 (1981), S. 872-875 
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    AIChE Journal 27 (1981), S. 876-876 
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    AIChE Journal 27 (1981), S. 881-888 
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We hereby submit three different numerical methods for the solution of the multicomponent distillation model for two partially immiscible liquids. A procedure to define the real number of phases present on each stage has been developed. The proposed Newton-Raphson method allows efficient solution of problems with a large selection of the unknowns and the specification equations.
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    AIChE Journal 27 (1981), S. 888-892 
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    Notes: Based on terLinden's (A. J. terLinden, “Investigations into Cyclone Dust Collectors,” IME Proc., 160, 233, 1949) experimental observations, a three-region model is proposed for the fluid flow in a cyclone. Within each region, turbulence is assumed to promote mixing of the suspended particles. Incorporation of this mixing concept into the three-region model allows an analytic expression for the collection efficiency of the cyclone to be developed.The theoretical result is compared with data obtained in the high temperature, high pressure exhaust from a pressurized fluidized bed combustor.
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    AIChE Journal 27 (1981), S. 920-927 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A series of seven coals were oxidized in a fixed bed reactor to determine the controlling reaction regimes during mild coal oxidation. The effects of coal porosity and particle size, reactor temperature, and oxygen partial pressure were evaluated. The results show that coal-oxygen reactions are controlled by the rate of internal gaseous diffusion for most coals, and by the rate of chemical reaction for the most porous coal of the set tested. Particle size effects also suggest internal diffusional control. Determinations of cumulative oxygen deposition indicate that surface areas several orders of magnitude greater than the superficial surface can participate in oxidation reactions, putting in doubt the applicability of the model previously derived by Kam et al. (1976a) for external mass transfer control.
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    AIChE Journal 27 (1981), S. 946-951 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel experimental setup allowed both the kinetics of the thermal cracking of ethane and of the coke formation to be studied over a temperature range extending from 750 to 870°C. The overall kinetics of ethane disappearance are in excellent agreement with previously reported pilot results. Coking rates are initially high but rapidly decrease to reach an asymptotic value. The initial product distribution also differs from the asymptotic product distribution. A kinetic model for the coking is derived from the experiments and used in conjunction with a set of conservation equations for the simulation of industrial ethane cracking. The predicted run length, thickness of the coke layer and evolution of the tubeskin temperatures are in agreement with industrial observations.
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    AIChE Journal 27 (1981), S. 984-993 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical model of venturi scrubber performance consisting of the governing differential equations for momentum, material, and energy exchange is solved using a Milne fourth-order predictor - Hamming corrector numerical integration procedure. The model provides for specification of the operating variables, including scrubber geometry, throat gas velocity, liquid to gas loading ratio, and collector droplet and particle-size distributions. Liquid loading ratio and gas velocity are shown to be the two most important operating variables, while the dispersity of the droplet size distribution only slightly affects collection efficiency over the operating range normally encountered. Location of the liquid injection site and length of the throat are also important design considerations. While particle collection in venturi scrubbers has typically been assumed to occur in the potential flow regime, the present results show that collection can also occur under conditions corresponding to viscous flow about the collecting droplets. The transition Reynolds number used to change from the potential to viscous flow equations affects the predicted performance.
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    AIChE Journal 27 (1981), S. 1024-1026 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 1035-1038 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 1-4 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 27 (1981), S. 20-25 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The trend observed on variation of the operating conditions during CO oxidation on platinum in a CSTR is as follows: stable states → simple oscillations → multipeak oscillations → stable states. Analysis of the experimental results indicates that a third or higher order system of differential equations is necessary to describe most of the observations.
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    AIChE Journal 27 (1981), S. 26-32 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A branched pore kinetic model for aqueous phase activated carbon adsorption is presented in which the carbon particle is separated into rapidly and slowly diffusing regions. The model was developed to overcome problems arising from a single rate parameter analysis and is shown to describe experimental data well. In addition to very different rates of transport in the two regions, parameters estimated by regression analysis indicated differences in the adsorptive characteristics.
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