Dimethyl sulfate (DMS) is a highly toxic and reactive chemical compound with the formula (CH₃O)₂SO₂. While its use has declined in recent years due to safety concerns, there are still a few applications of dimethyl sulfate in the chemical industry. However, it is important to note that handling dimethyl sulfate requires specialized knowledge, appropriate safety measures, and compliance with strict regulations.

Here are some of the historical applications of dimethyl sulfate:

1. Methylation Agent: Dimethyl sulfate is primarily known for its use as a methylation agent in the synthesis of organic compounds. It can methylate a variety of functional groups, including amines, alcohols, phenols, and thiols. This reaction is often employed in the production of pharmaceuticals, dyes, pesticides, and other fine chemicals.

2. Chemical Intermediates: Dimethyl sulfate is used as an intermediate in the synthesis of various chemical compounds. For example, it is involved in the production of certain surfactants, quaternary ammonium compounds, and cationic polymers. These compounds find applications in detergents, hair care products, fabric softeners, and water treatment chemicals.

3. Herbicides and Pesticides: Dimethyl sulfate has been historically used in the production of herbicides and pesticides, particularly in the synthesis of some organophosphate compounds. However, due to safety concerns, alternative methods and safer chemicals have largely replaced the use of dimethyl sulfate in this context.