Proton-transfer mechanism in the decarboxylation of ammonium trichloroacetate in acetonitrile

Abstract

The rate constants, k, for the decomposition of ammonium trichloroacetate in acetonitrile were determined at 298 K BHCCl₃COO [graphic omitted] CHCl₃+ CO₂+ B where B is an N-base. The first-order decarboxylation of trichloroacetic acid in the presence of N-bases is strongly dependent upon proton transfer in ([graphic omitted]) complexes.

Discussion of the rate constants, k, obtained shows 3 types of complexes in the proton-transfer mechanism, i.e. a symmetrically positioned proton, and without proton transfer for 2 cases: [graphic omitted]. The sigmoidal curve of rate constants, – log k, plotted against pK^AN_a(BH⁺) describes the location of the proton in the hydrogen bridge. The behaviour of (CCl₃COOHR)^– complexes has many similarities to the molecular complexes, CCl₃COOHB, discussed above. Implications of these results for carboxylate additives in overbased lubricating oils are discussed.