The formation of β-muonium-substituted cyclopentyl and cycloheptyl radicals, and the significance of the A′µ/AH isotope ratio in relation to the conformations of muonium-substituted alkyl radicals

Abstract

From the coupling constants obtained from a wide variety of β-muonium-substituted alkyl radicals and their protiated analogues, we conclude that the preference for the conformation in which the β-C—Mu bond eclipses the singly occupied orbital depends largely on hyperconjugative effects, although steric effects become more important as the size of the substituents at the radical centre is increased. Cyclic radicals, including the β-muonium-substituted cyclopentyl and cycloheptyl radicals, are discussed with respect to the ‘limiting isotope ratio’ towards which all alkyl radicals should tend at high temperatures, according to hyperconjugation theory. We conclude that the value of this limiting ratio is 1.18 ± 0.05.