Dimethyl sulfate

Dimethyl sulfate (DMS) 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 Me₂SO₄, where CH₃ or Me is methyl. Me₂SO₄ is mainly used as a methylating agent in organic synthesis. Me₂SO₄ is a colourless oily liquid with a slight onion-like odour. Like all strong alkylating agents, Me₂SO₄ is toxic.^[3] Its use as a laboratory reagent has been superseded to some extent by methyl triflate, CF₃SO₃CH₃, the methyl ester of trifluoromethanesulfonic acid.

Dimethyl sulfate

Names
Preferred IUPAC name Dimethyl sulfate
Other names Dimethyl sulphate; Sulfuric acid dimethyl ester; Me2SO4; DMSO4; Dimethyl ester of sulfuric acid; Methyl sulfate, di-
Identifiers
CAS Number	77-78-1 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:59050 Y
ChEMBL	ChEMBL162150 Y
ChemSpider	6252 Y
ECHA InfoCard	100.000.963
KEGG	C19177 Y
PubChem CID	6497
UNII	JW5CW40Z50 Y
CompTox Dashboard (EPA)	DTXSID5024055
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[1]
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)[1]
Magnetic susceptibility (χ)	−62.2×10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Extremely toxic, contact hazard, inhalation hazard, corrosive, environmental hazard, carcinogenic, mutagenic
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H314, H317, H330, H335, H341, H350
NFPA 704 (fire diamond)	4 2 1
Flash point	83 °C; 182 °F; 356 K[1]
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)[2]
LCLo (lowest published)	97 ppm (human, 10 min)[2]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 ppm (5 mg/m3) [skin][1]
REL (Recommended)	Ca TWA 0.1 ppm (0.5 mg/m3) [skin][1]
IDLH (Immediate danger)	Ca [7 ppm][1]
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 verify (what is YN ?) Infobox references

History

Impure dimethyl sulfate was prepared in the early 19th century.^[4] J. P. Claesson later extensively studied its preparation.^[5][6]

It was investigated for possible use in chemical warfare in World War I^[7][8] in 75% to 25% mixture with methyl chlorosulfonate (CH₃ClO₃S) called "C-stoff" in Germany, or with chlorosulfonic acid called "Rationite" in France.^[9]

The esterification of sulfuric acid with methanol was described in 1835:^[10]

2 CH₃OH + H₂SO₄ → (CH₃)₂SO₄ + 2 H₂O

Production

Dimethyl sulfate is produced commercially by the continuous reaction of dimethyl ether with sulfur trioxide:^[3]

CH₃OCH₃ + SO₃ → (CH₃)₂SO₄

Dimethyl sulfate can be synthesized in the laboratory by several methods.^[11] The reaction of methyl nitrite and methyl chlorosulfonate also results in dimethyl sulfate:^[6]

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

Reactions and uses

Dimethyl sulfate is a reagent for the methylation of phenols, amines, and thiols. One methyl group is transferred more quickly than the second. Methyl transfer is assumed to occur via an S_N2 reaction. Compared to other methylating agents, dimethyl sulfate is preferred by the industry because of its low cost and high reactivity.

Methylation at oxygen

Commonly dimethyl sulfate is employed to methylate phenols.^[12][13]

C₆H₅ONa + (CH₃O)₂SO₂ → C₆H₅OCH₃ + Na(CH₃O)SO₃Na

In some cases, simple alcohols are also methylated, as illustrated by the conversion of tert-butanol to t-butyl methyl ether:

(CH₃)₃COH + (CH₃O)₂SO₂ →(CH₃)₃COH + Na(CH₃O)SO₃H

The methylation of sugars is called Haworth methylation.^[14] The methylation of ketones is called the Lavergne reaction.

Methylation at amine nitrogen

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

C₆H₅CH=NC₄H₉ + (CH₃O)₂SO₂ → C₆H₅CH=N⁺(CH₃)C₄H₉[CH₃OSO₃]⁻

Quaternized fatty ammonium compounds are used as a surfactant or fabric softener. Methylation to create a tertiary amine is illustrated as:^[13]

CH₃(C₆H₄)NH₂ + (CH₃O)₂SO₂ (in NaHCO₃ aq) → CH₃(C₆H₄)N(CH₃)₂ + Na(CH₃)SO₄

Methylation at sulfur

Thiolate salts are easily methylated by Me₂SO₄ to give methyl thioethers:^[13]

RSNa + (CH₃O)₂SO₂ →CH₃SR + Na(CH₃O)SO₃Na

In a related example:^[15]

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

This method has been used to prepare thioesters from thiocarboxylic acids:

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

Reactions with nucleic acids

Dimethyl sulfate (DMS) is used to determine the secondary structure of RNA. At neutral pH, DMS methylates unpaired adenine and cytosine residues at their canonical Watson–Crick faces, but it cannot methylate base-paired nucleotides. Using the method known as DMS-MaPseq,^[16] RNA is incubated with DMS to methylate unpaired bases. Then the RNA is reverse-transcribed; the reverse transcriptase frequently adds an incorrect DNA base when it encounters a methylated RNA base. These mutations can be detected via sequencing, and the RNA is inferred to be single-stranded at bases with above-background mutation rates.

Dimethyl sulfate can effect the base-specific cleavage of DNA by attacking the imidazole rings present in guanine.^[17] Dimethyl sulfate also methylates adenine in single-stranded portions of DNA (for example, those with proteins like RNA polymerase progressively melting and re-annealing the DNA). Upon re-annealing, these methyl groups interfere with adenine-guanine base-pairing. Nuclease S1 can then be used to cut the DNA in single-stranded regions (anywhere with a methylated adenine). This is an important technique for analyzing protein-DNA interactions.

Alternatives

Although dimethyl sulfate is highly effective and affordable, its toxicity has encouraged the use of other methylating reagents. Methyl iodide is a reagent used for O-methylation, like dimethyl sulfate, but it is less hazardous and more expensive.^[15] Dimethyl carbonate, which is far less reactive, has far lower toxicity compared to both dimethyl sulfate and methyl iodide.^[18] High pressure can be used to accelerate methylation by dimethyl carbonate. In general, the toxicity of methylating agents is correlated with their efficiency as methyl transfer reagents.

Safety

Dimethyl sulfate is carcinogenic^[19] and mutagenic, highly poisonous, corrosive, and environmentally hazardous.^[20] It is absorbed through the skin, mucous membranes, and gastrointestinal tract, and can cause a fatal delayed respiratory tract reaction. An ocular reaction is also common. There is no strong odor or immediate irritation to warn of lethal concentration in the air. The LD₅₀ (acute, oral) is 205 mg/kg (rat) and 140 mg/kg (mouse), and LC₅₀ (acute) is 45 ppm per 4 hours (rat).^[21] The vapor pressure of 65 Pa^[22] is sufficiently large to produce a lethal concentration in air by evaporation at 20 °C. Delayed toxicity allows potentially fatal exposures to occur prior to development of any warning symptoms.^[20] Symptoms may be delayed 6–24 h. Concentrated solutions of bases (ammonia, alkalis) can be used to hydrolyze minor spills and residues on contaminated equipment, but the reaction may become violent with larger amounts of dimethyl sulfate (see ICSC). Although the compound hydrolyses, treatment with water cannot be assumed to decontaminate it.

One hypothesis regarding the apparently mysterious 1994 "toxic lady" incident is that the person at the centre of the incident had built up dimethyl sulfone crystals in her blood, which were converted by an unknown mechanism to dimethyl sulfate vapour that poisoned attending medical staff.^[23][24]

References

1. NIOSH Pocket Guide to Chemical Hazards. "#0229". National Institute for Occupational Safety and Health (NIOSH).
2. "Dimethyl sulfate". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
3. Weisenberger, Karl; Mayer, Dieter; Sandler, Stanley R. (2000). "Dialkyl Sulfates and Alkylsulfuric Acids". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a08_493. ISBN 978-3-527-30385-4.
4. Dumas, J.; Péligot, E. (1835). "Mémoire sur l'esprit de bois et sur les divers composés ethérés qui en proviennent" [Memoir on spirit of wood [i.e., methanol] and on various ethereal compounds that come from it]. Annales de Chimie et de Physique. 2nd series (in French). 58: 5–74.
5. Claesson, Peter (1879). "Ueber die neutralen und sauren Sulfate des Methyl- und Aethylalkohols" [On the neutral and acid sulfates of methyl and ethyl alcohol]. Journal für praktische Chemie. 2nd series (in German). 19: 231–265. doi:10.1002/prac.18790190123.
6. Suter, C. M. (1944). The Organic Chemistry of Sulfur: Tetracovalent Sulfur substans. John Wiley & Sons. pp. 49–53. LCCN 44001248.
7. "Dimethyl Sulfate 77-78-1". EPA.
8. "Poison Facts: Low Chemicals: Dimethyl Sulfate". The University of Kansas Hospital.
9. Sartori, Mario (1939). The War Gases. D. Van Nostrand. pp. 262, 266.
10. Dumas, J.; Péligot, E. (1835). "Mémoire sur l'esprit de bois et sur les divers composés ethérés qui en proviennent" [Memoir on spirit of wood [i.e., methanol] and on various ethereal compounds that come from it]. Annales de Chimie et de Physique. 2nd series (in French). 58: 5–74.
11. Shirley, D. A. (1966). Organic Chemistry. Holt, Rinehart and Winston. p. 253. LCCN 64010030.
12. G. S. Hiers, F. D. Hager (1929). "Anisole". Organic Syntheses. 9: 12. doi:10.15227/orgsyn.009.0012.
13. "Dupont product information". Archived from the original on 2008-11-19. Retrieved 2006-05-08.
14. W. N. Haworth (1915). "III. A New Method of Preparing Alkylated Sugars". Journal of the Chemical Society, Transactions. 107: 8–16. doi:10.1039/CT9150700008.
15. Fieser, L. F.; Fieser, M. (1967). Reagents for Organic Synthesis. John Wiley & Sons. p. 295. ISBN 9780471258759.
16. Zubradt, Meghan; Gupta, Paromita; Persad, Sitara; Lambowitz, Alan; Weissman, Jonathan; Rouskin, Silvi (2017). "DMS-MaPseq for genome-wide or targeted RNA structure probing in vivo". Nature Methods. 14 (1): 75–82. doi:10.1038/nmeth.4057. PMC 5508988. PMID 27819661.
17. Streitwieser, A.; Heathcock, C. H.; Kosower, E. M. (1992). Introduction to Organic Chemistry (4th ed.). Macmillan. p. 1169. ISBN 978-0024181701.
18. Shieh, W. C.; Dell, S.; Repic, O. (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. PMID 11784197.
19. "Dimethyl Sulfate CAS No. 77-78-1" (PDF). 12th Report on Carcinogens (RoC). US Department of Health and Human Services. 2011.
20. Rippey, J. C. R.; Stallwood, M. I. (2005). "Nine Cases of Accidental Exposure to Dimethyl Sulphate — A Potential Chemical Weapon". Emergency Medicine Journal. 22 (12): 878–879. doi:10.1136/emj.2004.015800. PMC 1726642. PMID 16299199.
21. "Material Safety Data Sheet - Dimethyl sulfate MSDS". ScienceLab. Archived from the original on 2012-04-06. Retrieved 2011-10-02.
22. ICSC
23. "What's the story on the "toxic lady"?". The Straight Dope. 1996-03-22. Retrieved 2024-01-15.
24. Grant, P. M.; Haas, J. S.; Whipple, R. E.; Andresen, B. D. (1997-06-23). "A possible chemical explanation for the events associated with the death of Gloria Ramirez at Riverside General Hospital". Forensic Science International. 87 (3): 219–237. doi:10.1016/s0379-0738(97)00076-5. ISSN 0379-0738. PMID 9248041.

External links

• WebBook page for C2H6SO4
• International Chemic