In addition to their widespread use in industry and agriculture, dithiocarbamates have generated considerable interest as potential therapeutic agents. Delineating the mechanisms and chemical species responsible for the adverse effects reported for dithiocarbamates could help in designing dithiocarbamates that have structural properties that diminish the occurrence of these effects. One established metabolic pathway involves acid promoted decomposition to CS2, a well-recognized toxicant, and amine. In this investigation the influence of electronic and steric properties of nitrogen substituents upon the rate of decomposition is examined in a series of 21 dithiocarbamates. The data show that the decomposition of N,N-dialkyl dithiocarbamates follows first-order kinetics in buffered aqueous solutions near neutrality. Decomposition is initiated by a change in the hybridization of the nitrogen from sp2 to sp3 that facilitates transfer of the acid derived proton to nitrogen with a concomitant weakening of the nitrogen-thiocarbonyl bond and release of CS2. This proposed mechanism has two implications: (1) Nitrogen substituents that stabilize the developing positive charge make the dithiocarbamate more susceptible to acid promoted decomposition and (2) for a cyclic dithiocarbamate, the rate of decomposition is governed by its ring size.
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