摘要:

AbstractGangliosides are found in the brain and other organs, and are composed of sphingosine, fatty acids, hexoses, and sialic acid. Types of gangliosides differ in the fatty acids and the sugar residues. The carbohydrate residue in the quantitatively predominating brain gangliosides is ganglio‐N‐tetraose, a tetrasaccharide. In these gangliosides, this residue combines with one or more molecules of sialic acid. The oligosaccharide part is a carrier of serologic properties. Gangliosides are characteristic lipid components of some neuronal membranes in the central nervous system, and can be localized on the synaptic apparatus of nerve cells in the cerebral cortex. Their site of occurrence and physiological action point to their participation in the transmission of impulses. It was in the brains of the mentally ill that gangliosides were first discoverd, and indeed their pathologic accumulation can possibly be attributed to congenital defect of enzymes involved in their synthesis or metabolism. Gangliosides are produced from their components by acceptor‐specific transfe

ISSN:0570-0833    

DOI:10.1002/anie.196800871

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThermotropic mesomorphous phases such as occur in the melts of many organic substances are considered. Though mesomorphous melts were first observed by Reinitzer in 1888, fundamental structural problems regarding such melts have not, as yet, been completely solved. Part I of this article deals mainly with such structural problems and with the theories of crystalline organic liquids. Part II describes the use of nematic solvents for magnetic resonance studies on oriented molecules. Examples are given to illustrate the possibilities offered by this procedure, and some of the results obtained so far are reviewed.

ISSN:0570-0833    

DOI:10.1002/anie.196800971

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThe direct synthesis of organohalogenosilanes, particularly methyl‐ and phenylchlorosilanes, is the main process for the production of the monomers required for silicone polymers. This complex heterogeneous catalytic reaction involves the interaction of a gaseous component (the organic halide) with two solid components (silicon and copper), the relative quantities of which change as the reaction proceeds. The mechanism of the direct synthesis has not yet been conclusively established. The free‐radical mechanism originally proposed supposes the formation of organic free radicals. On the other hand, the chemisorption mechanism suggested later postulates the dissociative adsorption of the organic halide on the silicon‐copper double center (the silicon and the copper being joined by a chemical bond). The results obtained so far indicate that the chemisorption mechanism is of decisive importance, but it is not impossible that both mechanisms operate simultane

ISSN:0570-0833    

DOI:10.1002/anie.196801121

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

摘要:

AbstractThe mechanism of the Wolff‐Kishner reaction is discussed in the light of accumulated information about the kinetics, thermodynamics, and solvent effects of the process. Wolff‐Kishner reduction under normal conditions is thought to involve the trans hydrazone anion, which, in the rate‐determining step, exhibits a more or less concerted proton capture at the carbanion terminal and undergoes a solvent‐induced proton loss at the nitrogen terminal. The stereochemistry of the Wolff‐Kishner reduction is believed to be affected by the presence of “ortho” substituents and by a change to a nonpolar, aprotic reaction medium. The mechanism elaborated for the Wolff‐Kishner reduction is extended to the Wolff‐Kishner elimination and isomerization reactions. Conformational analysis of the intermediates permits correlation of the competitive reduction and elimination processes with the structures o

ISSN:0570-0833    

DOI:10.1002/anie.196801201

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196801281

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196801292

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196801301

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196801312

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196801321

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196801331

出版商:Hüthig&Wepf Verlag    

年代:1968

数据来源: WILEY