Kinetic electron spin resonance spectroscopy. Part III. Proton exchange rates for ketyl radicals in organic solvents

Abstract

Measurements of linewidths and hyperfine splittings in the e.s.r. spectra of some photochemically generated ketyl radicals have been used to determine the rates of acid-catalysed carboxy-proton exchange reactions in these species. For CH₃Ċ(OH)CO₂H radicals in chloroform, ethanol, and propan-2-ol the second-order rate constants k are 1·7, 2·0, and 2·8 × 10⁷ l mol^–1s^–1 respectively at 298 K and for HO₂CCH₂Ċ(OH)CO₂H radicals in ethanol k= 2·8 × 10⁷ l mol^–1s^–1. Measured activation energies are ca. 30 kJ mol^–1.