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The simultaneous formation of urea and carbonate from aqueous soh tions of ammonium, barium, or sodium cyanate has been studied near 60' and 80". The ionic strength was virtually constant at 0.25, and [OH-] ranged from 4 x 10-7 to 2 x 10-3. The rate of reaction was given bywhere the first term accounts for urea formation and the others are responsible for the production of carbonate. A first-order decomposition of urea to cyanate sometimes contributes slightly, and must be taken into account when considering the overall reaction. These rate equations permit an explanation of earlier observations, and other evidence indicates that they can be expected to apply whenever the pH is greater than 2. Borate ions and triethylamine do not affect the rate specifically.The Bronsted relations for acid and base catalysis apply to K and h',respectively, but general acid or base catalysis is not observed. It therefore seems likely that all the reactions involve nucleophilic addition to cyanic acid in the rate-determining step, with formation of carbonate occurring via carbamic acid or the carbamate ion. This mechanism is subject to the restriction that the addition complex resulting from this nucleophilic attack must be capable of forming urea, carbamic acid, or the carbamate ion by proton transfer and bond rupture. Any reactions of these complexes with water or hydroxide ions appear to be too slow to prevent return to the initial reactants, This accounts for the absence of catalysis by borate ions, triethylamine, or cyanate ions in the reactions of cyanic acid.INORGANIC cyanates decompose in aqueous solution to form urea and carbonate." When it is borne in mind that reactants and products will be partly present as their conjugate acids or bases, the reactions may be represented by the stoicheiometric equations* Throughout this paper the term carbonate is used collectively, and refers to all forms in which carbonates may be present, i.e., carbonate ions, hydrogen carbonate ions, carbonic acid, and carbon dioxide. Similarly, cyanate refers to cyanate ions and cyanic acid, and a m m o n i u m to ammonium ions and ammonia.

The heat capacity of activation for the solvolysis of benzyl chloride in 50% aqueous acetone and 50% aqueous ethanol has been determined. Two mechanistic explanations can be advanced to account for all the data now available for these reactions. Hydrolysis (or ethanolysis) may involve a single bimolecular reaction path, with an appreciable contribution of the valence-bond structure involving the carbonium ion, Ph*CH,+, to the structure of the transition state. Alternatively, a continuous " spectrum " of transition states may be available to the reactant, but only a small fraction, a t most, of the total solvolysis can proceed by unimolecular mechanisms. Concurrence of only the extreme forms of the two mechanisms is not supported by the evidence.