Specific ³H‐labelling by diimide reduction of unsaturated bonds. I. Mechanism of reductions with hydrazine in aprotic solvents

The applicability of aprotic solvents for hydrazine reductions was studied for labelling purposes and acetonitrile was found to be a favourable medium for this reaction. The reaction can be carried out in the absence of protons, but small amounts of acetic acid have a catalytic effect. Kinetic investigations have shown that oxygen supply in the medium is the rate‐determining step under the conditions applied. The mechanism of the reaction is discussed. No explanation can be given of the autocatalytic and acid‐catalysed acceleration of the reaction.