Free-radical reductions of arenediazonium ions in aqueous solution. Part I. Toluene-p-diazonium ions reduced with methanol

60 Co γ-Radiation has been used to initiate the free-radical reduction reaction (i) and the mechanism is shown to be as in reactions (ii)—(iv), where reactions (ii) and (iii) are the propagating steps and reaction (iv) the terminating ArN2++ CH3OH → ArH + N2+ CH2O + H+(i), Ar˙+ CH3OH → ArH +·CH2OH (ii), ArN2++·CH2OH → Ar˙+ CH2O + H++ N2(iii), Ar˙+ ArN2+→ products (iv) step. Pulse radiolysis shows reaction (ii) to be rate-determining. The photochemically induced reaction to yield the same products is shown to occur with quantum yields greater than unity. The products and importance of reaction (iv) with respect to some recent e.s.r. flow studies of Norman et al. is discussed.