Temprature dependence of the deuterium isotope effect in the deprotonation of some nitroalkanes by anionic bases

The temperature dependences of rates and deuterium isotope effects were determined for the deprotonation of 1‐phenyl‐1‐nitroethane (1), its analogue 1‐ d , 1‐phenyl‐2‐nitropropane (2) and its analogue 2‐ d by methoxide in methanol, ethoxide in ethanol, hydroxide/methoxide in 50% (v/v) methanol–water and hydroxide in water. The isotope effects varied little with substrate or solvent–base combination. k H / k D at 30°C was between 6·0 and 7·1 in all cases. The temperature dependences varied considerably [ A aH / A aD = 0·14–1·35 and E aD – E aH 0·95–2·29 kcal mol −1 (1 kcal = 4·184 kJ)]. A aH / A aD was lower with 1‐phenyl‐1‐nitroethane than with 1‐phenyl‐2‐nitropropane, but there was no consistent variation with solvent/base.