Electron spin resonance studies of reduction by solvated electrons in liquid ammonia. Part 7.—α,β-unsaturated carboxylic acids, esters and nitriles

Abstract

The technique of continuously mixing liquid ammonia solutions of solvated electrons (obtained by dissolving sodium) and a substrate in the cavity of an e.s.r. spectrometer has been applied to both acrylic acid and its homologues and the corresponding esters and also unsaturated dicarboxylic acids, all of which give rise to the radical-anion of the substrate. The radical-anion of trans-crotonitrile has also been characterised.With certain esters, s-cis- and s-trans-conformations of the radical-anion have been observed and the radical-anions of the esters of maleic and fumaric acids have been shown to interconvert. Assignment of coupling constants has been made by systematic substitution of protons by alkyl groups, etc., and confirmed both by simple MO calculations and by the INDO method. Reduction of acetylenic to ethylenic bonds has been observed on the ms timescale for phenylpropiolic acid and ethyl propiolate and anomalous spectral linewidths have been noted in the e.s.r. spectrum of the latter.