Conformational analysis of the EPR spectra of cyclohexenyl radical and some of its alkyl derivatives

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1975

DOI:https://doi.org/10.2172/4168122· OSTI ID:4168122

de Tannoux, Nancy M. ^[1]

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1. Univ. of Pittsburgh, PA (United States)

Electron paramagnetic resonance spectra have been obtained for radicals produced by x-irradiation of cyclohexene and various alkyl-substituted cyclohexenes trapped in an adamantane matrix. Temperature variations of these spectra permits determination of the enthalpy and entropy of activation for interconversion between the conformations. For cyclohexenyl radical, the enthalpy of activation is 6.81 ± 0.58 kcal/mole and the entropy of activation is -0.04 ± 2.38 e.u. Methyl substitution on C₁ gives a radical with activation parameters similar to the parent radical. Methyl groups attached to C₅ increase the activation parameters significantly. On the basis of these observations, it is suggested the cyclohexenyl radicals exist in two conformations of the same energy which are of the ''envelope'' type, with C₁, C₂, C₃, C₄, and C₆ coplanar. A model involving a planar transition state for the interconversion process is proposed which accounts for most of the experimental results.

• Research Organization: Univ. of Pittsburgh, PA (United States)
• Sponsoring Organization: US Energy Research and Development Administration (ERDA)
• NSA Number: NSA-33-006973
• OSTI ID: 4168122
• Report Number(s): COO--3435-24
• Country of Publication: United States
• Language: English

Related Subjects

*CYCLOALKENES-- RADIOLYSIS
*RADICALS-- ELECTRON SPIN RESONANCE
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* --Chemistry--Radiation Chemistry
ADAMANTANE
N40300* --Chemistry--Radiation Chemistry
X RADIATION