✦ LIBER ✦

Ionic and biradical mechanisms in thermal and photo cis-trans isomerizations

✍ Scribed by E.M. Evleth

Publisher: Elsevier Science
Year: 1969
Tongue: English
Weight: 235 KB
Volume: 3
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(69)80112-0

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✦ Synopsis

Receded 7 February 1969

Calculations on the planar and twisted configurations of a number of polyenes and related compounds show that photo and thermal isonerization occur through two, conceptually different mechanisms.

The cis-trans isomerization about a 'formal' double bond can, conceptually, occur through two different mechanisms. These mechanisms are classified as either biradical or ionic (zwitterionic) according to the principal resonance structures that can be written for the possible intermediate resulting from twisting the 'formal' double bond by 900. If A and B are substituents attached to a formal double bond then the intermediate resulting from this twisting can be written as follows:

A_CH=CH_B <t=CH-CH=t (biradi,ti)

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