preparation-dmmtav-dmdtav-using-dmav-for-environmental-applications

Preparation of DMMTAV and DMDTAV Using DMAV for Environmental Applications: Synthesis, Purification, and Confirmation

Dimethylated thioarsenicals such as dimethylmonothioarsinic acid (DMMTAV) and dimethyldithioarsinic acid (DMDTAV), which are produced by the metabolic ...

Korea Basic Science Institute, Seoul Center

Dimethylmonothioarsinic acid (DMMTA) is a highly toxic, thiolated analogue of dimethylarsinic acid (DMA). In comparison, a further thiolated analogue, dimethyldithioarsinic acid (DMDTA), and DMAboth exhibit lower toxicity. To understand the environmental conditions responsible for forming DMMTA, the kinetics of DMAthiolation are examined. The thiolation of DMAis pH-dependent and consists of two consecutive first-order reactions under excess sulfide conditions. The first thiolation of DMAto form DMMTAis faster than the second one to DMDTA. DMMTAis therefore an intermediate. The first reaction is first-order in HS at pH 6.0 and 20 °C; therefore, the overall reaction is second-order and the rate coefficient in this condition is 0.0780 Ms. The rate coefficient significantly decreases at pH 8.0, indicating that HS(aq) triggers the thiolation of DMA. The second reaction rate is significantly decreased at pH 2.5; therefore, reaction under strongly acidic conditions leads to accumulation of highly toxic DMMTAin the early stages of thiolation. The transformation of DMDTAto DMMTAis catalyzed in the presence of ferric iron. Formation of DMMTAshould be considered when assessing risk posed by arsenic under sulfidic or sulfate reducing conditions.

Hosub Lee

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