Dimethyl sulfate



Dimethyl sulfate
Other names Sulfuric acid, dimethyl ester; Me2SO4; DMSO4
Identifiers
CAS number 77-78-1
SMILES O=S(=O)(OC)OC
Properties
Molecular formula S
Molar mass 126.13 g/mol
Appearance Colorless liquid
Density 1.33 g/ml, liquid
Melting point

-32 °C

Boiling point

188 °C decomposes

Solubility in water Reacts with water
Solubility acetone
Hazards
Main hazards Poison, contact hazard, inhalation hazard, corrosive, environmental hazard, carcinogenic, mutagenic
R-phrases R45, R25, R26, R34,
R43, R68
S-phrases S45
Related Compounds
Related compounds Diethyl sulfate, methyl triflate, dimethyl carbonate
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Dimethyl sulfate is a organic synthesis.

Under standard conditions, Me2SO4 is a colourless oily trifluoromethanesulfonic acid.

History

Dimethyl sulfate was first discovered in the early 1800s in an impure form. P. Claesson later extensively studied its preparation.[1]

Production

Dimethyl sulfate can be synthesized in the laboratory by many different syntheses:[2]

2 CH3OH + H2SO4 → (CH3)2SO4 + 2 H2O

Another possible synthesis involves distillation of methyl hydrogen sulfate:[1]

2 CH3HSO4 → H2SO4 + (CH3)2SO4

Methyl nitrite and methyl chlorosulfonate also result in dimethyl sulfate[1]:

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

In the United States, Me2SO4 has been produced commercially since the 1920s. A common process is the continuous reaction of sulfur trioxide.[3]

(CH3)2O + SO3 → (CH3)2SO4

Uses

Dimethyl sulfate is best known as a reagent for the methylation of Dimethyl carbonate has far lower toxicity compared to both dimethyl sulfate and methyl iodide and can be used to instead of dimethyl sulfate for N-methylation.[5] In general the toxicity of methylating agents is correlates with their efficiency as methyl transfer reagents.

Methylation at oxygen

Most commonly, Me2SO4 is employed to methylate phenols. Some simple alcohols are also suitably methylated, as illustrated by the conversion of tert-butyl alcohol to t-butyl methyl ether:

2 (CH3)3COH + (CH3O)2SO2 → 2 (CH3)3COCH3 + H2SO4

Alkoxide salts are rapidly methylated:[6]

RO - Na + + (CH3O)2SO2 → ROCH3 + Na(CH3)SO4

Methylation at amine nitrogen

Me2SO4 is used to prepare both quaternary ammonium salts or tertiary amines:

C6H5CH=NC4C9 + (CH3O)2SO2 → C6H5CH=N+(CH3)C4C9 + CH3OSO3-

Quaternized fatty ammonium compounds are used as a surfactant or fabric softeners. The methylation of a tertiary amine is illustrated as[6]:

CH3(C6H2)NH2 + (CH3O)2SO2 (in HNCO2) → CH3(C6H2)N(CH3)2 + Na(CH3)SO4

Methylation at sulfur

Similar to the methylation of alcohols, mercaptide salts are easily methylated by Me2SO4[6]:

RS-Na+ + (CH3O)2SO2 → RSCH3 + Na(CH3)SO4

An example is:[4]

p-CH3C6H4SO2Na + (CH3O)2SO2 → p-CH3C6H4SO2CH3 + Na(CH3)SO4

This method has been used to prepare thioesters:

RC(O)SH + (CH3O)2SO2 → RC(O)S(CH3) + HOSO3CH3

Other Uses

With DNA dimethyl sulfate can effect the base-specific cleavage of imidazole rings present in guanine.[7] This process can be used to determine base sequencing, cleavage on the DNA chain, and other applications.

Safety

Dimethyl sulfate is likely methanol, which is less toxic than dimethyl sulfate.

References

  1. ^ a b c Suter, C. M. The Organic Chemistry of Sulfur Tetracovalent Sulfur Compounds John Wiley & Sons, Inc. 1944. p 49-53
  2. ^ Shirley, D. A. Organic Chemistry. Holt, Rinehart and Winston. 1966. p. 253
  3. ^ a b Substance Profiles - Dimethyl Sulfate. 11th Report on Carcinogens. Department of Health and Human Services.
  4. ^ a b Fieser, L. F. and Fieser, M. Reagents for Organic Synthesis. John Wiley & Sons, Inc. 1967. p. 295
  5. ^ W. C. Shieh, S. Dell and O. Repic (2001). "1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and Microwave-Accelerated Green Chemistry in Methylation of Phenols, Indoles, and Benzimidazoles with Dimethyl Carbonate". Organic Letters 3 (26): 4279-4281. doi:10.1021/ol016949n.
  6. ^ a b c Dupont product information
  7. ^ Streitwieser, A., Heathcock, C. H., and Kosower, E. M. Introduction to Organic Chemistry. Prentice-Hall Inc. 1992. p. 1169
  8. ^ Rippey, J. and Stallwood, M. Emergency Medicine Journal 2005;22:878-879
 
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