Kinetics of proton and deuteron transfer from α,4-dinitrotoluene to 1,8-bis(dimethylamino)naphthalene in alcoholic solvents

Abstract

Evidence is presented to show that the reaction between α,4-dinitrotoluene and 1,8-bis(dimethylamino)naphthalene, in either propan-2-ol or t-butyl alcohol as solvent, is a proton transfer from the carbon acid to the nitrogen base to give an ion pair. The second-order rate constants for the proton and deuteron transfer reactions have been determined over the temperature range 10–45 °C in the two solvents. The reactions are relatively slow and are characterized by enthalpies of activation of 10–14 kcal mol–1(42–58 kJ mol–1) and entropies of activation of –17 to –31 cal mol–1 K–1(–71 to –130 J mol–1 K–1). The isotopic rate ratios are small (kH/kD < 3), although ΔHD‡–ΔHH‡ is normal (ca. 1 kcal mol–1), with compensation by positive values for ΔSD‡–ΔSH‡.