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Multiple‐substituent effects on the isomerization of unsymmetrical cis ‐1,3‐diphenyltriazenes
Author(s) -
Zhang Huaibin,
Barra Mónica
Publication year - 2005
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.900
Subject(s) - chemistry , isomerization , substituent , photoisomerization , medicinal chemistry , cis–trans isomerism , reaction rate constant , stereochemistry , computational chemistry , catalysis , kinetics , organic chemistry , physics , quantum mechanics
Abstract Trans ‐to‐ cis photoisomerization of unsymmetrical 4,4′‐disubstituted trans ‐1,3‐diphenyltriazenes renders a non‐equilibrium mixture of two isomeric cis pairs which, as in the case of symmetrical 1,3‐diphenyltriazenes, undergo thermal cis ‐to‐ trans isomerization by means of 1,3‐prototropic rearrangements catalyzed by general acids and general bases. A quantitative analysis, by means of a multiple‐substituent Hammett equation, of the rate constants for restricted rotation around the N‐2—N‐3 bond in cis ‐1,3‐diphenyltriazenes renders ρ values of −1.93±0.08 and 0.82±0.08 for N‐1 and N‐3, respectively. Copyright © 2005 John Wiley & Sons, Ltd.