Cycloalkylmethyl radicals. Part 4.1 electron spin resonance study of conformational equilibria in cyclohexenylmethyl and 4-alkylcyclohexenylmethyl radicals

John C. Walton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

For cyclohex-2-enylmethyl and 4-alkylcyclohex-2-enylmethyl radicals the quasi-axial and the quasiequatorial conformers can both be observed by e.s.r. spectroscopy. Similarly, the axial and equatorial conformers of cyclohex-3-enylmethyl radical can be distinguished by e.s.r. spectroscopy. The conformational free-energy difference of the CH2’ group in the 2-position, -∆G°300., was found to be 0.17 ± 0.03 kcal mol-1 and in the 3-position -∆G°300 = 0.0 ± 0.1 kcal mol-1. The Arrhenius parameters for inversion of the half-chair conformation of cyclohex-2-enylmethyl radical were determined by line shape analysis of the exchange-broadened spectra and found to be: log(/kf/s-1) = 12.3 - (5.7 kcal mol_1)/2.3RT and log(/kb/s-1) = 12.0 - (5.5 kcal mol-1)/2.3RT. The barrier to rotation about the Cα-Cβ bond in a cyclohexenylmethyl radical is much less than the barrier in a cyclohexylmethyl radical because the former radical has only one syn-axial hydrogen on C(5) to impede the rotation whereas the latter radical has two syn-axial hydrogens on C(3) and C(5).

Original languageEnglish
Pages (from-to)1641-1646
Number of pages6
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number10
DOIs
Publication statusPublished - 1 Jan 1986

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