What molecule am I?
Dimethylmercury (Me2Hg) is one of the nastiest chemicals made by humans or found in nature. It was known as long ago as 1858, when English chemist/entomologist George B. Buckton isolated it during experiments with methyl- and ethylmercury compounds. It reappeared in the literature in 1899, when prominent French chemist Marcellin Berthelot found that under electrical discharge Me2Hg absorbs nitrogen gas.
In an early discovery of Me2Hg in the environment, Swedish researchers S. Jensen and A. Jernelöv reported in 1969 that it and its cationic degradation product, methylmercury1 (MeHg+), are produced in bottom sediments and rotten fish in mercury-contaminated waters. It didn’t help matters that MeHg+ had been used as a pesticide in Sweden until 1966 and contributed to the pollution.
Knowledge of the distribution of Me2Hg in oceans has been limited because of a lack of measurement methods. In a 2022 effort to combat this problem, Robert P. Mason and collaborators at the University of Connecticut (Groton) and the University of California, Santa Cruz, developed an automatic analyzer for the high-resolution measurement of Me2Hg and other volatile mercury molecules in surface ocean waters.
In 1971, two other Swedish scientists, Leif Bertilsson and Halina Y. Neujahr* at the University of Stockholm, demonstrated another way that methylmercury compounds are formed in nature. They showed that methylcobalamin2, a form of vitamin B12, reacts with mercury(II) ion in human and animal bodies to produce the deadly toxins.
The tragic death in 1997 of rising chemistry star Karen Wetterhahn at Dartmouth College (Hanover, NH) drove home the lethality of Me2Hg. While studying heavy-metal toxicity, Wetterhahn got a small amount of Me2Hg on her rubber gloves, which were later found to be permeable to the compound. She began to experience toxicity symptoms, and, less than a year after the exposure, she died. In 2022, the 25th anniversary of her death, Sam Lemonick wrote an account of Wetterhahn’s life and contributions to chemistry.
At one time, Me2Hg was used as a methylating agent in organic synthesis; but because of its toxicity, it has been replaced by safer reagents such as dimethylzinc, trimethylaluminum, and methylmagnesium halides (Grignard reagents).
For much more on the chemistry, toxicity, and environmental effects of Me2Hg, see the ScienceDirect information page.
1. CAS Reg. No. 22967-92-6.
2. CAS Reg. No. 13422-55-4.
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