ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Study of Microstructure and Residual Stresses in Dissimilar Al/Steels Welds Produced by Cold Metal Transfer (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 571-572 (Mar. 2008), p. 347-353 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Recently a new welding technique, the so-called ‘Cold Metal Transfer’ (CMT) techniquewas introduced, which due to integrated wire feeding leads to lower heat input and higherproductivity compared to other gas metal arc (GMA) techniques. Here microstructure formation andresidual stress state in dissimilar steel to aluminum CMT welds are investigated. The intermetallicphase seam between the filler and the steel is only a few micrometers thick. Residual stress analysesreveal the formation of the typical residual stress state of a weld without phase transformation. Bothin longitudinal and in transversal direction compressive residual stresses exist in the steel plateparent material, tensile residual stresses are present in the heat affected zone of the steel and thealuminum alloy. The area containing tensile residual stresses is larger in the aluminum alloy due toits higher heat conductivity than in the steel. Due to the symmetry in the patented voestalpinewelding geometry and the welding from bottom and face side of the weld, the residual stressdistributions at the top and at the bottom side of the weld are very similar
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/18/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.571-572.347.pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Enzymatic and chromatographic chiral discrimination of racemic (thio)glycidyl esters: Part I. A chemoenzymatic approach to both enantiomers of thioglycidyl esters (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 250-254 
    Details
    ISSN: 0899-0042
    Keywords: enzymic kinetic resolution ; porcine pancreatic lipase (PPL) ; hydrolysis ; transesterification ; acylation ; enol esters ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both hitherto unknown (+)-(R)- and (-)-(S)-thioglycidyl esters, (R)-(2) and (S)-(2), have been synthesized with different high enantiomeric excesses (ee) by two routes from the corresponding rac-glycidyl esters rac-(1). The first includes a porcine pancreatic lipase (PPL)-mediated kinetic resolution of these esters followed by sulfuration with practically complete inversion to the (+)-(R)-enantiomer (+)-(R)-(2) (36-86% ee). (-)-(S)-Thioglycidyl esters (-)-(S)-(2) are obtained by the reverse reaction sequence (43-80% ee). In the latter case the hydrolysis rate is lower than that of analogous glycidyl esters. Moreover, the dependence of enantiomeric excess on the size of the acyl-group is of the opposite tendency. Therefore, in both cases suitable selection of the acid residue gives rise to maximum enantioselectivity. The irreversible lipase-catalyzed acylation of rac-glycidol and rac-thioglycidol, however, was found to be a less suitable alternative. The enantiomeric excess of recovered homochiral esters was determined by chiral chromatography using modified cellulose stationary phases (OB, OD). © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050412
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Enzymatic and chromatographic chiral discrimination of racemic (thio)glycidyl esters: Part II. Optical resolution of racemic (thio)glycidyl esters on modified cellulose chiral stationary phases (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 255-257 
    Details
    ISSN: 0899-0042
    Keywords: cellulose tris(3,5-dimethylphenyl carbamate) ; cellulose tribenzoate ; chiral HPLC ; enantiomers ; temperature dependence ; chiral recognition ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral chromatography on cellulose tris(3,5-dimethylphenyl carbamate) (Chiralcel OD) and cellulose tribenzoate (Chiralcel OB) coated stationary phases has been successfully used for the optical resolution of rac-(thio)glycidyl esters (acetate, propionate, butyrate). Glycidyl esters could sufficiently be resolved on the OD column whereas for the thio analogues baseline resolution is obtained on CSP OB using hexane/2-propanol mobile phases. The separation factor (α) and resolution (RS) depend on column temperature, eluent composition, and flow rate, respectively. Best results were obtained for the butyrates and at low temperatures in general. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050413
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Preparative scale enantioseparation of 1-cyclohexyl-1-phenylethyl hydroperoxide and 1,2,3,4-tetrahydro-1-naphthyl hydroperoxide on a modified cellulose stationary phase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 243-247 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; cellulose tris(3,5-dimethylphenyl carbamate) ; hydroperoxides ; enantiomers ; circular dichroism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analytical and preparative scale optical resolution of 1-cyclohexyl-1-phenylethyl hydroperoxide and 1,2,3,4-tetrahydro-1-napthyl hydroperoxide has been achieved by chiral HPLC on a cellulose tris(3,5-dimethylphenyl carbamate) stationary phase coated on silica gel. The method has been used to obtain several hundred milligrams of highly enriched enantiomers (%ee 〉98) which were characterized by [α]D and circular dichroism spectra, respectively. Configurational assignments were achieved for 1,2,3,4-tetrahydro-1-naphthyl hydroperoxide enantiomers. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070410
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of β -Cyperone via Fungal Hydroxylation of thujone-derived tricyclic cyclopropanes (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1707-1720 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of optically active sesquiterpenes with a eudesmane C-skeleton from the chiral starting material thujone involves transformation of a tricyclic intermediate (1R,2R,4S)-1,7-dimethyl-4-(1-methylethyl)tricyclo[4.4.0.02,4]dec-6-en-8-one (2) into the bicyclic compound β -cyperone (5). Hydroxylation of 2 at C(5) or C(11) permits subsequent opening of the cyclopropane ring and rearrangement to β -cyperone. In this publication, studies involving hydroxylation of 2 by fungal cultures are presented. The resultant products are useful intermediates in efficient synthesis of eudesmane sesquiterpenes. Of five fungi tested, Rhizopus oryzae ATCC 11145 proved most versatile. It hydroxylates at the exocyclic C(11) position in high yield (70%) and, to a lesser extent, at C(5) (5%). Enzymatic activity appears at the end of growth phase and at least 2.2 g of 2 per liter can be metabolized without significant loss of product yield. A second fungus, Cunninghamella echinulata ATCC 9244, proved most useful for hydroxylation of derivatives of 2 for the preparation of derivatives of β -cyperone, although product yields were low (2-20%), some derivatives were nonreactive, and hydroxylation at C(9) occurred. The relationship between precursor structure and enzyme affinity is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770704
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Enantiomerically pure 7-oxabicylo[2.2.1]hept-5-en-zyl derivatives as synthetic intermediates. Part IIIPart I, see [1]; Part II, see [2].. Total synthesis of D- and L-ribose derivativesFor a preliminary communication, see Y. Auberson, R. Bimwala, J. Wagner, P. Vogel, Société Suisse de Chimie, Berne, 16 Oct. 1987, Abstract p. 29. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 624-630 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure methyl 5-bromo-5-deoxy-2,3-O- isopropylidene-β-D- (D-5b) and -β-l-ribofuranoside (l-5b) have been derived from (-)-(1R,2S,4R)-2-exo-cyano-7-oxabicylo[2.2.1]hept-5-en-endo,-yl (1′S)-camphanate (1) and (+)-(1S,2R,4S)-2-exo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl(1′R)-camphanate (2), respectively, in 5 synthetic steps and 28% overall yield. Hydrolysis of D-5b and L-5b afforded methyl 2,3-O isopropylidene-β-D-ribofuranoside (D-5a) and methyl 2,3-O-isopropylidene β-L-ribofuranoside (L-5a), respectively. The intermediate (+)-(1R,4R,5R,6R) 5-exo,6-exo-(isopropylidenedioxy)-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7) and its enantiomer(-)-7 were also obtained enantiomerically pure by resolution of (=)-7 by the Johnson-Zeller method. In bothe approaches, the chiral auxiliaries ((-)- and (+)-camphanic acids, or (+)-(S)-N,S-dimethyl-S-phenylsulfoximide) were recovered at an early stage of the synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710316
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Induktion und Variation von Chiralität in discotisch-flüssigkristallinen Polymeren (1990)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 102 (1990), S. 1525-1528 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19901021255
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    N,N,N′,N′-Tetramethylethylendiamin-di(tert-butyl)aluminium-Kationen  -  Molekülstruktur des [(Me3C)2Al · TMEDA]⊕[(Me3C)2AlBr2]⊖ (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 612 (1992), S. 25-34 
    Details
    ISSN: 0044-2313
    Keywords: Reaction of dimeric di(tert-butyl)aluminium halides with tetramethylethylendiamine ; symmetrical and unsymmetrical cleavage ; aluminium cations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: (N,N,N′,N′ -tetramethylethylendiamine) di(tert-butyl)aluminium Cations  -  Molecular Structure of [(Me3C)2Al(TMEDA)]⊕[(Me3C)2AlBr2]⊖Dimeric di(tert-butyl)aluminium halides (Me3C)2AlX (X = Cl, Br) react with N,N,N′,N′ -tetramethylethylendiamine (TMEDA) to give three compounds: the salt-like [(Me3C)2Al(TMEDA)]⊕[(Me3C)2AlX2]⊖ 1, characterized by crystal structure determination, and [(Me3C)2Al(TMEDA)]⊕X⊖ 3 both with chelating amine, and the more covalent, pentane soluble (Me3C)2AlX(TMEDA) 2 with TMEDA bound by only one nitrogen atom. The reaction resembles the symmetrical and unsymmetrical cleavage of diborane(6). 3 (X = Cl) is also formed by treatment of 1 with boiling n-hexane in the presence of TMEDA over a period of 24 hours, while for X = Br the more covalent 2 is the main product under similar conditions. In solution 2 decomposes slowly yielding different products in dependency of the solvent: in benzene 3 and in n-pentane 1 are formed.
    Notes: Die dimeren Di(tert-butyl)halogenalane (Me3C)2AlX (X = Cl, Br) reagieren mit N,N,N′,N′-Tetramethylethylendiamin (TMEDA) in heißem Benzol zu insgesamt drei Verbindungen: den salzartigen Derivaten [(Me3C)2Al (TMEDA)]⊕[(Me3C)2AlX2]⊖ 1, die, wie die Kristallstrukturbestimmung am entsprechenden Bromderivat zeigt, im Festkörper isolierte Anionen und Kationen aufweisen, den ebenfalls salzartigen [(Me3C)2Al(TMEDA)]⊕X⊖ 3 und den eher kovalenten, in n-Pentan löslichen (Me3C)2AlX(TMEDA) 2, in denen das Amin nicht mehr chelatartig an das Aluminiumatom, sondern nur noch über ein Stickstoffatom gebunden ist. Die Reaktion gleicht damit der symmetrischen und unsymmetrischen Spaltung des Diborans(6). 2 ist in Lösung unbeständig und wandelt sich je nach Lösungsmittel zu unterschiedlichen Produkten um: in Benzol bildet sich 3, aus n-Pentan scheidet sich 1 ab. Mehrstündiges Behandeln von 1 mit siedendem n-Hexan in Gegenwart von wenig TMEDA ergibt für X = Cl das Monohalogenidderivat 3, für X = Br aber die kovalente Verbindung 2.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926120106
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Trialkylhydridoalanate RxR′3-xAlH⊖ [R = CMe3; R′ = CH(SiMe3)2] (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 613 (1992), S. 67-75 
    Details
    ISSN: 0044-2313
    Keywords: Trialkylalanes ; tert-butyl lithium ; β-elimination ; hydridoalanates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Trialkylhydridoalanates RxR′3-xAlH⊖ [R = CMe3; R′ = CH(SiMe3)2]The very strong base tert-butyl lithium reacts in the presence of chelating tetramethylethylendiamine with the aluminium organyls Al[CH(SiMe3)2]2CMe3 1 and Al[CH(SiMe3)2](CMe3)2 2 not under proton abstraction from the C—H acidic elementorganic substituent, but under β-elimination and addition of the thereby formed LiH to the coordinatively unsaturated aluminium atom. Two alanates  -  [Hal{CH(SiMe3)2}2CMe3]⊖ 3 and [HAl{CH(SiMe3)2}(CMe3)2]⊖ 4 each with Li(TMEDA)2⊕ as counterion  -  were isolated; they exhibit separate anions and cations in solid state as shown by a crystal structure determination on 3. In absence of the chelating amine tert-butyl lithium decomposes under the catalytic effect of the aluminium compound to LiH, which does not add to aluminium and precipitates in a reactive form.
    Notes: Die starke Base tert-Butyllithium reagiert mit den gemischt substituierten tert-Butyl[bis(trimethylsilyl)methyl]alanen Al[CH(SiMe3)2]2CMe3 1 und Al[CH(SiMe3)2](CMe3)2 2 in Gegenwart des Chelatbildners Tetramethylethylendiamin (TMEDA) nicht unter Deprotonierung am elementorganischen Substituenten, sondern unter β-Eliminierung und Anlagerung des gebildeten LiH an das koordinativ ungesättigte Aluminiumatom. Dabei entstehen die Hydridoalanate [HAl{CH(SiMe3)2}2CMe3]⊖ 3 und [HAl{CH(SiMe3)2}(CMe3)2]⊖ 4 jeweils mit Li(TMEDA)2⊕ als Gegenion, die, wie die Kristallstrukturbestimmung an 3 zeigt, im Festkörper isolierte Anionen und Kationen aufweisen. In Abwesenheit des Chelatliganden zersetzt sich das tert-Butyllithium unter dem katalytischen Einfluß des Aluminiumorganyls bei Zimmertemperatur zu LiH, das nicht an Aluminium angelagert wird und in reaktiver Form ausfällt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19926130112
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Thermolyse sterisch überladener Alanate; Synthese zweier neuer 1-Sila-3-alanata-cyclobutan-Derivate mit AlC2Si-Heterozyklus (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 249-257 
    Details
    ISSN: 0044-2313
    Keywords: C—H acidic alanates ; deprotonation of bis(trimethylsilyl)methyl groups ; AlC2Si heterocycles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolysis of Sterically Stressed Alanates; Synthesis of Two New 1-Sila-3-alanata-cyclobutane Derivatives with Four-membered AlC2Si-HeterocyclesThe reaction of high shielded alkyl or aryl alanes with LiCH(SiMe3)2 in the presence of the chelating N,N′,N″-trimethyl-triazinane yields the sterically stressed alanates [(Me3C)2Al{CH(SiMe3)2}2]- 12 and [R—Al{CH(SiMe3)2}3]- (R = Me3SiCH2 13, Et 14, Me 15, C6H5 16) each with a Li(triazinane)2 counter ion. On thermolysis of the sterically most shielded derivatives 12 and 13 at 130 to 150°C one equivalent of bis(trimethylsilyl)methane is liberated, and by deprotonation of methyl groups carbanionic species are formed, which are stabilized by intramolecular coordination to the unsaturated aluminium atoms under formation of AlC2Si heterocycles (19 and 20). 20 was characterized by a single crystal structure determination. The remaining alanates give under similar conditions either under dismutation the recently published heterocycle 1 with two intact CH(SiMe3)2 groups (14 and 15) or a methyl alanate by the replacement of a elementorganic substituent (16).
    Notes: Durch Umsetzung sterisch hoch abgeschirmter Alkyl- oder Arylalane mit LiCH(SiMe3)2 in Gegenwart des Chelatbildners N,N′,N″-Trimethyltriazinan sind die sterisch überladenen Alanate [(Me3C)2Al{CH(SiMe3)2}2]- 12 und [R—Al{CH(SiMe3)2}3]- (R = Me3Si—CH2 13, Et 14, Me 15, C6H5 16) jeweils mit dem Li(Triazinan)2-Gegenion zugänglich. Beim Erwärmen der Alanate im festen Zustand auf 130 bis 150°C beobachtet man für die sterisch am höchsten abgeschirmten Derivate 12 und 13 die Freisetzung eines Äquivalents Bis(trimethylsilyl)methan; eine Methylgruppe eines CH(SiMe3)2-Rests wird deprotoniert, und die entstehenden Carbanionen stabilisieren sich jeweils durch intramolekulare Bindung zu einem Al-Atom. Dabei bilden sich die viergliedrigen AlC2Si-Heterozyklen 19 und 20, von denen 20 kristallstrukturanalytisch charakterisiert wurde. Die Alanate 14 und 15 reagieren unter Dismutierung zu dem bereits länger bekannten Heterozyklus 1 mit zwei intakten CH(SiMe3)2-Gruppen, und das Phenylalanat 16 ergibt unter Austausch eines elementorganischen Substituenten gegen eine Methylgruppe das Methylalanat 23.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210214
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...