Free-radical reductions of arenediazonium ions in aqueous solution. Part III. Kinetics of reactions of toluene-p-diazonium ions with ethanol, propan-2-ol, and acetaldehyde

Abstract

The kinetics of the radiation induced chain reaction between toluene-p-diazonium ions (ArN₂⁺) and the reducing agents ethanol, propan-2-ol, and acetaldehyde (RH₂) is consistent with a mechanism involving both α- and β-hydrogen abstraction from RH₂ by the p-tolyl radical. The ratio k_α/k_β for these reactions has been determined for each of the reducing agents above. α-ṘH Radicals reduce diazonium ions and propagate the chain. β-ṘH Radicals react either with RH₂ to give α-ṘH radicals [reaction (11)] or with ArN₂⁺ in a chain-terminating step [reaction (12)]. The rate constant ratios k₁₁/k₁₂ have been determined and the ratio is larger for acetaldehyde than for the alcohols. The reasons for this and the nature of reaction (12) are discussed, and it is postulated that the β-ṘH radicals add to the terminal nitrogen of the diazonium ions.