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  • 1
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Work reported earlier had shown that the addition of 0.07 micron stearate coated ultrafine precipitated CaCO3 (CUPCC) in medium to high molecular weight PVC resulted in a significant improvement in notched Izod impact strength. The improvement was much more dramatic when the filler loading exceeded 10 phr. The addition of CUPCC to low molecular weight PVC had practically no effect on the notched Izod impact strength at equivalent loadings. More recent studies have demonstrated that when CUPCC is added to an impact modified low molecular weight PVC, it dramatically enhances the efficiency of impact modifier. This was found to be consistent with threee general classes of commercially available impact modifiers used in this study. The ability to extend the impact modifier with CUPCC in low molecular weight PVC, which has gained a wide acceptance in injection molding operations, will result in significant cost savings. The effect of CUPCC addition on other key properties and cost benefits will also be presented.
    Additional Material: 10 Ill.
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  • 2
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [Bis(trimethylsilyl) methylene] (diisopropylamino) borane: an Allene-Type N = B = C SystemThe title compound iPr2N=B=C(SiMe3)2 (4) is formed as a storable colourless liquid by the elimination of FSiMe3 from F-(iPr2N)B-C(SiMe3)3 (3) at 520°C. The compounds O=CHPh and Me3SiN3 are added to the B=C bond of 4 to give the [2 + 2] cycloaddition product 5 and the [2 + 3] cycloaddition product 6, respectively. The alkylideneaminoborane 4 crystallizes in the space group P21/n. Perpendicular planes through C2NB and BCSi2 define an allene-type structure with a linear N=B=C skeleton, bond lengths 136.3 (N=B) and 139.1 pm (B=C).
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0009-2940
    Keywords: Alkylidenoboranes ; 1,2-Oxaboretanes ; 1,2,4-Azasilaboretidines ; 2,3-Diiminoboretane ; Borylsilyldiazomethane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions at the BC Double Bond of iPr2N=B=C(SiMe3)2By thermal elimination of propene and migration of a methyl group at 500-600°C, the alkylidenoaminoborane iPr2N=B=C(SiMe3)2 (1b) is transformed to the azasilaboretidine [-N(iPr)=B(Me)-CH(SiMe3)-SiMe2-] (2). Protic agents HX (X = Cl, Br, OMe, OiPr, NMe2, NEt2) are added to 1b to give iPr2N=B(X)-CH(SiMe3)2 (3a-f); products 3g, h of the same type (X = O—CR=CH2, R = tBu, Ph) are formed from 1b and ketones MeRCO. Products iPr2N=B(X)-C(SiMe3)2-Y [X = Y = Br: 4; X = Me, Y = Li(tmeda): 5] are isolated from the reaction of 1b with the unpolar Br2 or with LiMe, respectively; adduct 5 can be hydrolyzed to 3i (X = Me, Y = H) by HCl. The bromoboration of 1b by MeBBr2 or BBr3 gives iPr2N=B(Br)-(Z)C(SiMe3)-BBrMe (Z = SiMe3: 6a; Z = SiMe2Br: 6b). The CO group of aldehydes RCHO [R = Me, tBu, C(Me)=CH2], ketones PhRCO (R = Me, Ph), and ethyl acetate undergo a [2+2] cycloaddition with 1b to give oxaboretanes [-B(NiPr2)-C(SiMe3)2-CRR′-O-] (7a-f); starting with HCONMe2, the cycloaddition to 1b is followed by ring opening and the migration of a silyl group to yield (iPr2N)B(OSiMe3)-C(SiMe3)=CH(NMe2) (8). Azides RN3 (R = Ph, PhCH2) may be added to 1b with loss of N2, azaboriridines [-(iPr2N)B—C(SiMe3)2-NR-] (9a, b) being formed, whereas Me3SiN3 gives the diazo compound (iPr2N)B[N(SiMe3)2]-C(SiMe3)=N2 (10). The formation of the boretane [-(iPr2N)B—C(SiMe3)2-C(=NtBu)-C(=NtBu)-] (11) is observed from the 2:1 reaction of tBuN≡C with 1b. The alkylidenoaminoborane H14C7N=B=C(SiMe3)2 (1c; H14C7N = 2,6-dimethylpiperidino) is synthesized by a procedure similar to the synthesis of 1b and gives reactions similar to those of 1b: thermal cyclisation to the azasilaboretidine 12, addition of HNMe2 to give 3j, [2 + 2] cycloaddition of RCHO (R = tBu, Ph) and Ph2CO to give 7g-i.
    Notes: Das Alkylidenaminoboran iPr2N=B=C(SiMe3)2 (1b) geht bei 500-600°C unter Propenabspaltung und Methylwanderung in das Azasilaboretidin [-N(iPr)=B(Me)-CH(SiMe3)-SiMe2-] (2) über. Protische Stoffe HX (X = Cl, Br, OMe, OiPr, NMe2, NEt2) addieren sich an 1b zu iPr2N=B(X)—CH(SiMe3)2 (3a-f); die Produkte 3g, h desselben Typs (X = O—CR=CH2; R = tBu, Ph) erhält man mit Ketonen MeRCO. Weiterhin kann man an 1b das unpolare Br2 sowie LiMe unter Bildung von iPr2N=B(X)—C(SiMe3)2-Y addieren [X = Y = Br: 4; X = Me, Y = Li(tmeda): 5]; 5 wird durch HCl zu 3i verseift (X = Me, Y = H). Die Bromoborierung von 1b mit MeBBr2 und BBr3 führt zu iPr2N=B(Br)—(Z)C(SiMe3)-BBrMe (Z = SiMe3: 6a; Z = SiMe2Br: 6b). Die CO-Gruppe von Aldehyden RCHO [R = Me, tBu, C(Me)=CH2], Ketonen PhRCO (R = Me, Ph) und Ethylacetat geht mit der BC-Bindung von 1b [2 + 2]-Cycloadditionen zu den Oxaboretanen [-B(NiPr2)-C(SiMe3)2-CRR′-O-] (7a-f) ein; im Falle von HCONMe2 folgt der Cycloaddition eine Silylverschiebung unter Ringöffnung zu (iPr2N)B(OSiMe3)-C(SiMe3)=CH(NMe2) (8). Azide RN3 (R = Ph, PhCH2) addieren sich an 1b unter Abspaltung von N2 zu den Azaboriridinen [-(iPr2N)B—C(SiMe3)2-NR-] (9a, b), während das Azid Me3SiN3 unter Silylwanderung die Diazoverbindung (iPr2N)B[N(SiMe3)2]-C(SiMe3)=N2 (10) ergibt. Mit tBuN≡C reagiert 1b im Verhältnis 2:1 zum Boretan [-(iPr2N)B—C(SiMe3)2-C(=NtBu)-C(=NtBu)-] (11). Das Alkylidenaminoboran H14C7Nd—B=C(SiMe3)2 (1c, H14C7N = 2,6-Dimethylpiperidino) bildet sich ähnlich und reagiert analog 1b: thermische Cyclisierung zum Azasilaboretidin 12, Addition von HNMe2 zu 3j, [2+2]-Cycloaddition von RCHO (R = tBu, Ph) und Ph2CO zu 7g-i.
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  • 4
    ISSN: 0009-2940
    Keywords: Alkylideneboranes ; Boron, two-coordinated ; 1,2-Oxaboretane derivatives ; 1,2,4-Azadiboretidine derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkylaklyideneboranes R—B=C(Sime3)2: Isolable molecules with a Two-Coordinated Sextet Boron AtomThe colourless, liquid, pyrophoric alkylalkylideneboranes R—B=CA2 (2c, d: R = Me, tBu; A = SiMe3) are formed from Me(MeO)B—CA3 and tBu(F)B-CA3 by elimination of AOMe at 560°C and AF at 490°C, respectively. At ambient temperature 2d can be stored, whereas 2c cyclodimerizes to form 5. 2d crystallizes at 225 K; a structure determination at 120 K reveals the C—B=C skeleton to be linear with BC bond lengths of 154.7 and 136.1 pm. The adduct 6 and the [2 + 2] cycloadducts 7a, 8 are formed from 2c and 2,6-dimethylpyridine, benzophenone, and the iminoborane tBuB≡NtBu, respectively. 2d gives the cycloadduct 7b with benzophenone.
    Notes: Die farblosen, flüssigen, pyrophoren Alkylalkylidenborane R—B=CA2 (2c, d: R = Me, tBu; A = SiMe3), bilden sich aus Me(MeO)B—CA3 bzw. tBu(F)B—CA3 durch Abspaltung von AOMe bei 560°C bzw. von AF bei 490°C. Bei 25°C ist 2d lagerfähig, während sich 2c zu 5 cyclodimerisiert. In 2d, das bei 225 K kristallisiert, findet man bei 120 K ein lineares C—B=C-Gerüst mit BC-Bindungslängen von 154.7 und 136.1 pm. Mit 2,6-Dimethylpyridin bildet 2c das Addukt 6 und mit Benzophenon bzw. dem Iminoboran tBuB≡NtBu die [2 + 2]-Cycloaddukte 7a und 8; 2d reagiert mit Benzophenon zu 7b.
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  • 5
    ISSN: 0021-8758
    Source: Cambridge Journals Digital Archives
    Topics: English, American Studies , History , Political Science , Sociology , Economics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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