Dimethyl sulfate

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Dimethyl sulfate
Other names
Dimethyl ester of sulfuric acid
Dimethyl sulphate
Methyl sulfate
Sulfuric acid dimethyl ester
Molar mass 126.13 g/mol
Appearance Colorless, oily liquid
Odor Faint, onion-like
Density 1.333 g/cm3 (25 °C)
Melting point −32 °C (−26 °F; 241 K)
Boiling point 188 °C (370 °F; 461 K) (decomposes)
Solubility Miscible with acetone, dichloromethane, methanol
Vapor pressure 0.1 mmHg (20 °C)
Safety data sheet Sigma-Aldrich
Flash point 83 °C (182 °F; 356 K)
Lethal dose or concentration (LD, LC):
205 mg/kg (rat, oral)
140 mg/kg (mouse, oral)
Related compounds
Related compounds
Sulfuric acid
Sodium methyl sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Dimethyl sulfate is a chemical compound with chemical formula (CH3O)2SO2. As the diester of methanol and sulfuric acid, its formula is often written as (CH3)2SO4 or Me2SO4, where CH3 or Me is methyl.



Dimethyl sulfate reacts exothermically with water, to give sulfuric acid and methanol.

(CH3O)2SO2 + 2 H2O → H2SO3 + 2 CH3OH


Dimethyl sulfate is a colorless oily liquid with a slight onion-like odor (although smelling it would represent significant exposure). It reacts with water, but it's miscible with many organic solvents, such as methanol and halocarbons.


Dimethyl sulfate is sold by chemical suppliers. Due to its high toxicity, it's extremely difficult to acquire this compound.


Dimethyl sulfate can be prepared by reacting sulfur trioxide with anhydrous methanol or dimethyl ether.

SO3 + 2 CH3OH → (CH3O)2SO2 + H2O
SO3 + (CH3O)2O → (CH3O)2SO2

Thermal decomposition of sodium methyl sulfate yields dimethyl sulfate:

2 CH3NaSO4 → Na2SO4 + (CH3)2SO4

Methyl nitrite and methyl chlorosulfonate also result in dimethyl sulfate:

CH3ONO + (CH3)OSO2Cl → (CH3)2SO4 + NOCl


  • Methylating agent
  • Make methyl esters
  • Preparation of quaternary ammonium salts and tertiary amines



Dimethyl sulfate is corrosive and highly poisonous. Like all strong alkylating agents, Me2SO4 is extremely toxic, to both touch and inhalation. Dimethyl sulfate is absorbed through the skin, mucous membranes, and gastrointestinal tract, and can cause a fatal delayed respiratory tract reaction. There is no strong odor or immediate irritation to warn of lethal concentration in the air.


Should be kept in an airtight container, inside another larger container filled with a neutralizing medium. A lided bucket with sand may be used.


The compound can be neutralized by very carefully adding it dropwise to crushed ice, then an alkali is gently added until all the remaining acid is neutralized. This procedure must be done outside or in a remote location.


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