Naphthoyl σ-radicals: elucidation of their conformational behaviour by electron spin resonance

Abstract

The relative conformer stability in a series of naphthoyl σ-radicals has been investigated by e.s.r. techniques over a wide temperature range. In the case of the 1-naphthoyl radical two rotamers, with a conformational ratio apparently different from that of the parent molecule, were detected. In contrast, in the 2-naphthoyl radical the relative amounts of the conformers are, most likely, dependent upon those in the precursor aldehyde. Structural assignments were achieved by comparing the experimental data with INDO h.f.s. constants. The steric effect on the ratio of the conformers caused by methyl substituents was also examined in order to ascertain the reliability of the INDO approximation.