Kinetics of Dimethylated Thioarsenicals and the Formation of Highly Toxic Dimethylmonothioarsinic Acid in Environment

Youn Tae Kim, Hosub Lee, Hye On Yoon, Nam C. Woo

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


Dimethylmonothioarsinic acid (DMMTAV) is a highly toxic, thiolated analogue of dimethylarsinic acid (DMAV). In comparison, a further thiolated analogue, dimethyldithioarsinic acid (DMDTAV), and DMAV both exhibit lower toxicity. To understand the environmental conditions responsible for forming DMMTAV, the kinetics of DMAV thiolation are examined. The thiolation of DMAV is pH-dependent and consists of two consecutive first-order reactions under excess sulfide conditions. The first thiolation of DMAV to form DMMTAV is faster than the second one to DMDTAV. DMMTAV is therefore an intermediate. The first reaction is first-order in H2S at pH 6.0 and 20 °C; therefore, the overall reaction is second-order and the rate coefficient in this condition is 0.0780 M-1 s-1. The rate coefficient significantly decreases at pH 8.0, indicating that H2S(aq) triggers the thiolation of DMAV. The second reaction rate is significantly decreased at pH 2.5; therefore, reaction under strongly acidic conditions leads to accumulation of highly toxic DMMTAV in the early stages of thiolation. The transformation of DMDTAV to DMMTAV is catalyzed in the presence of ferric iron. Formation of DMMTAV should be considered when assessing risk posed by arsenic under sulfidic or sulfate reducing conditions.

Original languageEnglish
Pages (from-to)11637-11645
Number of pages9
JournalEnvironmental Science and Technology
Issue number21
Publication statusPublished - 2016 Nov 1

Bibliographical note

Funding Information:
This research was supported by a grant from the Korea Basic Science Institute (project no. T35760). Youn-Tae Kim was supported by the National Research Foundation of Korea (NRF) and the Center for Women In Science, Engineering and Technology (WISET) Grant under the Program for Returners into R and D (project no. KW-2016-0046). We thank Giehyeon Lee for providing valuable advice and Joo-Hee Chung for her support during ESI-MS measurements.

Publisher Copyright:
© 2016 American Chemical Society.

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry


Dive into the research topics of 'Kinetics of Dimethylated Thioarsenicals and the Formation of Highly Toxic Dimethylmonothioarsinic Acid in Environment'. Together they form a unique fingerprint.

Cite this