Diethyl sulfate

Diethyl sulfate is an organosulfur compound with the formula ₂SO₄. It occurs as a colorless, oily liquid with a faint peppermint odor. It is a toxic, combustible, and likely carcinogenic chemical compound. Diethyl sulfate is used as an ethylating agent.

Structure and properties

Although the formula for diethyl sulfate is typically written ₂SO₄, a more descriptive formula would be ₂SO₂. It is a diester of sulfuric acid. Sulfur is tetrahedral.
Diethyl sulfate hydrolyzes readily, forming ethanol and ethyl sulfate. Eventually sulfuric acid is formed with excess water.

Diethyl sulfate is used to an alkylating agent to prepare ethyl ethers, ethyl amines and ammonium salts, and ethyl thioethers. In preparing ethyl esters of fatty acids, both equivalents of the ethyl electrophile are transferred, unlike the usual alkylation of phenoxides:
Both dimethyl sulfate and diethyl sulfate react with inorganic nucleophiles as well. For example, potassium iodide gives ethyl iodide.

Diethyl sulfate cannot be prepared efficiently analogously to the method used for dimethyl sulfate. The reaction of oleum with diethyl ether results in excessive oxidation of the ethyl groups. Instead, diethyl sulfate is prepared in two steps starting from chlorosulfuric acid:
The resulting ethyl sulfate is then heated with sodium sulfate, leading to a redistribution reaction:

Like other strong alkylating agents and especially dimethyl sulfate, diethyl sulfate is toxic and genotoxic. It is classified as a Group 2A carcinogen by the IARC. Experimentation with animals has suggested this compound is likely carcinogenic to humans as it was implicated in the development of laryngeal cancer. Evidence of the effects of this chemical compound on reproductive or developmental health is also lacking.

Dialkyl sulfates can be rendered nontoxic by treatment with aqueous ammonia.