Dimethyl sulfate

Dimethyl sulfate is a colorless, sweet-smelling, very toxic liquid. It is the dimethyl ester of sulfuric acid and is available in moderate yield from methanol and H2SO4. It is an extremely potent alkylating agent in chemical synthesis . Its toxicity is based on the alkylation of DNA and proteins.

In Europe, the largest production facility is operated by Grillo-Werke AG in the Höchst industrial park in Frankfurt.

The abbreviation DMS, which is frequently used, is ambiguous as it is also used for dimethyl sulfide, dimethyl sulfone and dimethyl sulfite. Mixing up the substances is dangerous because of their different properties.

The synthesis takes place by reacting dimethyl ether with sulfur trioxide (SO3). Up until the 1980s, this was the main use of dimethyl ether, in 1998 about 15,000 t of the 50,000 t produced in Central Europe were converted into dimethyl sulfate.

The sulfate ion is a very weak nucleophile and thus an excellent leaving group in an SN reaction. This is what gives dimethyl sulfate its powerful ability to methylate. At room temperature only one methyl group reacts at first; when heated, both methyl groups can be used.

Dimethyl sulfate is used in laboratories and technology for the methylation of carboxylic acids, amines, phenols and other compounds. It is a raw material used in the manufacture of cosmetics,fabric softeners,paints,pharmaceuticals and agricultural products. In molecular biology, it was used as a reagent for the methylation of the base guanine(G), which precedes a specific strand break in sequencing

Dimethyl sulfate is clearly classified as carcinogenic and suspected to be mutagenic in humans . It can diffuse quickly through intact skin. Due to its alkylating effect, dimethyl sulfate is a strong poison for the mucous membranes and lungs. The carcinogenic effect of dimethyl sulfate is based on this: The DNA is methylated and can no longer be read, the poisoned cell dies or mutates. The liver, kidneys, heart and nervous system are also attacked. Due to the sulfuric acid produced during hydrolysis, dimethyl sulfate also has a strong corrosive effect. According to Appendix II, No. 6 of the German Hazardous Substances Ordinance (GefStoffV), the substance is classified as a particularly dangerous carcinogenic substance and may only be manufactured or used in closed facilities.

Extreme caution is required when working with the substance. Since there is no warning effect (odorless, no acute irritant effect), dangerous quantities can easily be absorbed unnoticed. After a latency period of around six to twelve hours, severe burns of the airways follow. It is essential to wear special protective gloves and to work in a fume cupboard that pulls well. Any residues of dimethyl sulfate must be destroyed in a mixture of 10% monoethanolamine, 30% butyl diglycol and 60% water.