摘要:

AbstractStereoselective synthesis is attracting more and more attention. Successful stereoselective syntheses require the availability of reactions of known stereochemistry which give maximum yields of the desired products. This is particularly so with reactions proceedingviacyclic transition states. Of these, the stereochemistry of [3,3]sigmatropic processes has long been known. This article now summarizes the factors determining the stereoselectivity of [2,3]sigmatropic rearrangememts.

ISSN:0570-0833    

DOI:10.1002/anie.197905633

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractAn adiabatic photoreaction is a chemical process that occurs entirely on a single excited electronic energy surface. As a rule, most photoreactions of organic molecules start on an excited electronic surface but “jump” to a lower surface somewhere along the reaction coordinate. There are, however, exceptions to this general rule. For example, photoreactions involving small structural changes and minor alterations in covalent bonding (e.g., proton transfer and complex formation) are commonly found to occur adiabatically. The purpose of this review is to survey examples of more complicated adiabatic photoreactions such as fragmentation, electrocyclic rearrangements, and geometrical isomerizations. The concepts employed are presented in an introductory discuss

ISSN:0570-0833    

DOI:10.1002/anie.197905721

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractAnions of sodium, potassium, rubidium, and cesium are stable both in suitable solvents and in crystalline solids. The latter can be prepared either by cooling a saturated solution or by rapid solvent evaporation. Thermodynamic arguments show that alkali metal anions can probably exist in saturated solutions of the alkali metals in any compatible solvent, but that below saturation, dissociation into the cation and solvated electrons is favored in highly polar solvents such as ammonia. The key to solvent‐free salts of the alkali metal anions is stabilization of thecationby incorporation into a suitable crown or cryptand complex. By using such complexes it also appears possible to produce “electride” salts in which the charge of the complexed cation is balanced by a trapped electron. The chemical, electrical, and optical properties of salts of the alkali metal anions and “electrides” could provide useful app

ISSN:0570-0833    

DOI:10.1002/anie.197905871

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe present article is concerned with the practical and theoretical aspects of gelation in protein systems. The processes involved are,inter alia, so complicated that several types of protein molecule assemblies and conformational changes during the association have to be considered. The gel network can be stabilized by five types of interaction: covalent crosslinking, polar interactions, hydrogen bonding, salt bridges and hydrophobic interactions. The microstructures of gels formed from fibrillated proteins (collagen) and from globular proteins (e.g.α‐ and β‐ casein) differ considerably. Of practical interest are methods of controlling the solubility of gels, includinge.g.the use of cross‐linking agents and addition o

ISSN:0570-0833    

DOI:10.1002/anie.197905991

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197906111

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197906121

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197906142

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197906151

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197906161

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197906171

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY