Jump to main content
Jump to site search

Issue 6, 1988
Previous Article Next Article

Captodative effect on rates of addition reactions of arylthiyl radicals to disubstituted olefins

Abstract

The rate constants for the addition reactions of the para-substituted phenylthiyl radicals (ZC6H4Ṡ) to disubstituted olefins (CH2[double bond, length as m-dash]CXY) have been determined by the flash photolysis method. The substituents X and Y in the olefins were chosen in order to obtain kinetic evidence for a captodative effect on the free-radical addition reactions in which the captodative radicals (PhSCH2ĊXY) were formed. When X was an electron-withdrawing (captive) group such as CN, electron-donating (dative) substituents (Y) accelerated the reactions of the olefins with the arylthiyl radicals. The order of acceleration is as follows: NR2 > OR > Cl > OC([double bond, length as m-dash]O)CH3 > CH3 > H. This result was interpreted in terms of a lowering of the activation energy caused by captodative stabilization of the transition state. For substituted propenes [CH2[double bond, length as m-dash]C(Y)CH3], the rate constants for addition increase with the electron-withdrawing power of the substituents Y. Localization energies for captodative-substituted olefins, from MO calculations, are well correlated with the kinetic data obtained in this study.

Back to tab navigation
Please wait while Download options loads

Article type: Paper
DOI: 10.1039/P29880000869
Citation: J. Chem. Soc., Perkin Trans. 2, 1988, 869-873
  •   Request permissions

    Captodative effect on rates of addition reactions of arylthiyl radicals to disubstituted olefins

    O. Ito, Y. Arito and M. Matsuda, J. Chem. Soc., Perkin Trans. 2, 1988, 869
    DOI: 10.1039/P29880000869

Search articles by author