Determination Rapide de la Configuration Cis Trans des Alcenes CHCHCH Utilisation des Complexes de Terres Rares
✍ Scribed by G. J. Martin; N. Naulet; F. Lefevre; M. L. Martin
- Publisher
- John Wiley and Sons
- Year
- 1972
- Tongue
- English
- Weight
- 481 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
In Z-CH-CH=CH-Y compounds (Z or Y being an alkyl group) the ethylenic part of the spectra is often very complex and the 3J(H-C=C-H) coupling constant which is a good tool for determining the configuration, is not easily determined. We have studied such allylic derivatives and many configurations have been assigned through stereospecific synthesis. Except a very few cases, 6 CH(Z) of the cis isomer is larger than 6 CHZ of the trans isomer. In alcohols RCH=CH-CHOHR' the stereoisomers behave differently in solutions with europium, praseodymium, holmium and dysprosium complexes. The spectra of the trans isomers remain strongly coupled but 3J(H-C==C-H) becomes easy to measure in the cis compounds.
R6sum6-Dans les compos6s de structure Z CH-CH=CH-Y la complexit6 du spectre rend souvent dificile I'obtention du couplage J(H-C=C-H) et donc l'identification de la configuration. L'etude de nombreux derives de ce type prtparks par des mCthodes stCr6ospCcifiques montre qu'B de rares exceptions pres, le deplacement chimique 6 CH(Z) de I'isomkre cis est suptrieur B 6,,(Z) de I'isomkre trans. Dans le cas des alcools R CH=CH CHOH R les isomkres configurationnels ont des comportements diffkrents en presence de complexes d'europium ou de praseodyme, holmium et dysprosium. Si le spectre des isomeres trans reste fortement coup16 en presence de complexe I'obtention de 3J(H-C=C-H) devient aisCe dans les composes cis.