Diethyl sulfate is primarily used as an ethylating agent in organic synthesis. It is commonly employed in the production of ethyl derivatives of various compounds, such as dyes, pharmaceuticals, and fragrances. In the pharmaceutical industry, it plays a role in the synthesis of certain drugs by introducing ethyl groups into molecules. Additionally, it is utilized in the manufacture of ethyl esters, which are important in the production of flavors and perfumes. However, due to its toxic and potentially carcinogenic nature, handling requires strict safety measures and controlled environments.