Abstract
The catalytic efficiencies of several alkylthioureas in N-nitrosodimethylamine formation were compared in aqueous acetate buffer of pH 4.0. The rate law, v0=kT[dimethylamine]0[nitrite]0[alkylthiourea]0, is suggested for the initial rate of the catalytic reaction, where the concentration terms represent initial stoichiometric concentrations of the indicated species. No clear-cut explanation could be given for the variation, within a factor of ten, of the kT value with the structure of the thioureas. However, the overall catalytic efficiency of the thioureas, or the net rate of nitrosamine formation, is shown to depend not only on the kT value but also on the rate of decomposition of the thioureas. Thus, the marked difference in the efficiency of thiourea and tetramethylthiourea, which have similar kT values, is ascribed to the faster decomposition of thiourea as compared with its tetramethyl derivative.
