Diethyl sulfate

Diethyl sulfate (DES) is an organosulfur compound with the formula (C₂H₅)₂SO₄.^[1][2] It occurs as a colorless, oily liquid with a faint peppermint odor. It is toxic, combustible, and likely carcinogenic chemical compound.^[3][2] Diethyl sulfate is used as an ethylating agent.

Diethyl sulfate

Diethyl sulfate
Names
Preferred IUPAC name Diethyl sulfate
Other names Sulfuric acid diethyl ester
Identifiers
CAS Number	64-67-5 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:34699
ChEMBL	ChEMBL163100 Y
ChemSpider	5931 Y
ECHA InfoCard	100.000.536
KEGG	C14706 Y
PubChem CID	6163
RTECS number	WS7875000
UNII	K0FO4VFA7I Y
CompTox Dashboard (EPA)	DTXSID1024045
InChI InChI=1S/C4H10O4S/c1-3-7-9(5,6)8-4-2/h3-4H2,1-2H3 Y Key: DENRZWYUOJLTMF-UHFFFAOYSA-N Y InChI=1/C4H10O4S/c1-3-7-9(5,6)8-4-2/h3-4H2,1-2H3 Key: DENRZWYUOJLTMF-UHFFFAOYAR
SMILES O=S(=O)(OCC)OCC
Properties
Chemical formula	C4H10O4S
Molar mass	154.18 g·mol−1
Appearance	Colorless liquid
Density	1.2 g/mL
Melting point	−25 °C (−13 °F; 248 K)
Boiling point	209 °C (408 °F; 482 K) (decomposes)
Solubility in water	decomposes in water
Vapor pressure	0.29 mm Hg
Magnetic susceptibility (χ)	−86.8·10−6 cm3/mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H312, H314, H332, H340, H350
Precautionary statements	P201, P202, P260, P261, P264, P270, P271, P280, P281, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P308+P313, P310, P312, P321, P322, P330, P363, P405, P501
NFPA 704 (fire diamond)	3 1 1
Flash point	104 °C (219 °F; 377 K)
Related compounds
Related compounds	Dimethyl sulfate; diethyl sulfite
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

Structure and properties

Although the formula for diethyl sulfate is typically written (C₂H₅)₂SO₄, a more descriptive formula would be (C₂H₅O)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.

Reactions

Diethyl sulfate is used to an alkylating agent to prepare ethyl ethers, ethyl amines^[4] 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:^[1]

2 RCO₂Na + (C₂H₅O)₂SO₂ → 2 RCO₂C₂H₅ + Na₂SO₄

Both dimethyl sulfate and diethyl sulfate react with inorganic nucleophiles as well. For example, potassium iodide gives ethyl iodide.

Preparation

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:^[1]

ClSO₃H + C₂H₅OH → C₂H₅OSO₃H + HCl

The resulting ethyl sulfate is then heated with sodium sulfate, leading to a redistribution reaction:

2 C₂H₅OSO₃H + Na₂SO₄ → (C₂H₅O)₂SO₂ + 2 NaHSO₄

Safety

Like other strong alkylating agents and especially dimethyl sulfate, diethyl sulfate is toxic^[2] and genotoxic.^[5] It is classified as a Group 2A (probably carcinogenic to humans) carcinogen by the IARC.^[6] Experimentation with animals has suggested this compound is likely carcinogenic to humans as it was implicated in the development of laryngeal cancer.^[7] Evidence of the effects of this chemical compound on reproductive or developmental health is also lacking.^[8]

Neutralization

Dialkyl sulfates can be rendered nontoxic by treatment with aqueous ammonia.^[1]

Further reading

• Theodore, S.; Sai, P. S. T. (2001). "Esterification of Ethanol with Sulfuric Acid: A Kinetic Study". Canadian Journal of Chemical Engineering. 79 (1): 54–64. doi:10.1002/cjce.5450790109.