Eguilibrium Studies by Electron Spin Resonance. 17. The Effect of a Methyl Group on the Solution Electron Affinity of Nitrobenzene

Article abstract of DOI:10.1021/j100313a049

Electron spin resonance studies have shown that the free energy of electron transfer from the ion-associated anion radical of nitrobenzene to p-methylnitrobenzene (PhNO2^.-, Na⁺ + CH3-PhNO2 = PhNO2 + CH3-PhNO2^.-,Na⁺) in liquid ammonia is 1.52 kcal/mol.The free energies of ion association for both anion radicals were measured, and these values were used in a thermochemical cycle to obtain the free energy of electron transfer involving the unassociated ions.This free energy of electron transfer is 1.4 kcal/mol, which is identical with the difference in the electron affinities of PhNO2 and CH3-PhNO2 in the gas phase.It was found that the ion association constant increased from 320 to 381 for PhNO2^.- and from 380 to 450 for CH3-PhNO2^.- when the solvent is changed from ammonia to methylamine.The increase in the ion association constant caused by placing a methyl group on the solvent is "coincidentally" the same as that caused by placing it on the nitrobenzene anion radical.