The primary deuterium isotope effect has been measured for the proton transfer reaction from di-(4-nitropheny1)methane to t-butoxide ion in a solvent consisting of 10% v/v toluene in 1-butanol at a series of temperatures between 20 and 45 "C. The isotopic rate ratio, kH/kD, is 7.3 at 25 "C. The activation parameters showed an enthalpy of activation difference (AHD* -AHH*) of only ra. ) kcal mol-' and an entropy isotope effect (ASD* -ASH*) of -2.4 cal mol-' deg-I. The latter indicates, according to the theory of Bell, that tunnelling of the proton through the energy barrier is unimportant in this reaction. This result is compared to other reactions in the literature, in which tunnelling has been postulated to occur.

The equilibrium constants, the second-order rate constants, and the activation parameters have been determined for the proton transfer from di-(4-nitropheny1)methane to ethoxide ion in a series of mixed sol- [Traduit par le journal]Can.

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Die Gleichgewichtskonstanten, Geschwindigkeitskonstanten und Aktivierungsparameter für den Protonenübergang von Di‐(4‐nitrophenyl)‐methan zu dem Äthoxid‐ bzw. Butoxid‐ion in Äthanol/Acetonitrilbzw.