Dimethylsulfate

Dimethyl sulfate

Names
Other names Sulfuric acid dimethyl ester; Me2SO4; DMSO4; Dimethyl ester of sulfuric acid, Methyl sulfate
Identifiers
CAS Number	77-78-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:59050 Y
ChemSpider	6252 Y
ECHA InfoCard	100.000.963
KEGG	C19177 Y
PubChem CID	6497
InChI InChI=1S/C2H6O4S/c1-5-7(3,4)6-2/h1-2H3 Y Key: VAYGXNSJCAHWJZ-UHFFFAOYSA-N Y InChI=1/C2H6O4S/c1-5-7(3,4)6-2/h1-2H3 Key: VAYGXNSJCAHWJZ-UHFFFAOYAK
SMILES COS(=O)(=O)OC
Properties
Chemical formula	C2H6O4S
Molar mass	126.13 g/mol
Appearance	Colorless, oily liquid
Odor	faint, onion-like
Density	1.33 g/ml, liquid
Melting point	−32 °C (−26 °F; 241 K)
Boiling point	188 °C (370 °F; 461 K) (decomposes)
Solubility in water	Reacts
Solubility	Methanol, dichloromethane, acetone
Vapor pressure	0.1 mmHg (20°C)
Magnetic susceptibility (χ)	-62.2·10−6 cm3/mol
Hazards
Main hazards	Extremely toxic, contact hazard, inhalation hazard, corrosive, environmental hazard, carcinogenic, mutagenic
R-phrases (outdated)	R45, R25, R26, R34, R43, R68
S-phrases (outdated)	S53, S45, S30, S60, S61
NFPA 704	2 4 1
Flash point	83 °C; 182 °F; 356 K
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	8.6 ppm (rat, 4 hr) 75 ppm (guinea pig, 20 min) 53 ppm (mouse) 32 ppm (guinea pig, 1 hr)
LCLo (lowest published)	97 ppm (human, 10 min)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 1 ppm (5 mg/m3) [skin]
REL (Recommended)	Ca TWA 0.1 ppm (0.5 mg/m3) [skin]
IDLH (Immediate danger)	Ca [7 ppm]
Related compounds
Related compounds	Diethyl sulfate, methyl triflate, dimethyl carbonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

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

Under standard conditions, Me₂SO₄ is a colourless oily liquid with a slight onion-like odour (although smelling it would represent significant exposure). Like all strong alkylating agents, Me₂SO₄ is extremely toxic. Its use as a laboratory reagent has been superseded to some extent by methyl triflate, CF₃SO₃CH₃, the methyl ester of trifluoromethanesulfonic acid.

Dimethyl sulfate was first discovered in the early 19th century in an impure form. P Claesson later extensively studied its preparation. It was used in chemical warfare in WWI.

Dimethyl sulfate can be synthesized in the laboratory by many different syntheses, the simplest being the esterification of sulfuric acid with methanol:

Another possible synthesis involves distillation of methyl hydrogen sulfate:

Methyl nitrite and methyl chlorosulfonate also result in dimethyl sulfate:

Me₂SO₄ has been produced commercially since the 1920s. A common process is the continuous reaction of dimethyl ether with sulfur trioxide.