Diethyl carbonate

Chemical Properties

Diethyl carbonate is esters, beta-enamino esters, carbamates and unsymmetrical alkyl carbonates. It is a colourless liquid with a mild odour. Insoluble in water, soluble in alcohol, ether and other organic solvents.

Uses

Diethyl carbonate (DEC) is generally used in the C-alkoxycarbonylation of enolate anions, aryl and alkyl cyanides. It reacts with 1,2-amino alcohols to yield corresponding 2-oxazolidinones. Additionally, DEC is also used as a component of electrolyte solution in lithium ion batteries.

Production Methods

Diethyl carbonate (DEC), one of the most frequently used aliphatic carbonates, is produced by passing gaseous phosgene in boiling ethanol, in a molar ratio of 1 part of phosgene to 2.5 – 4 parts of ethanol, into a glass or enamel apparatus consisting of a heatable reaction vessel with a reflux condenser and a distillation setup. The reaction gives essentially quantitative yields (≥ 99 %) and also forms hydrogen chloride. Excess ethanol is removed from the reaction mixture by distillation, and DEC is obtained as the residue.
Manufacturing steps: (a) reacting chlorine and carbon monoxide to produce (COCl2); (b) reacting phosgene with ethyl alcohol to make ethyl chlorocarbonate (ClCO2C2H5); (c) reacting ethyl chlorocarbonate with anhydrous ethyl alcohol to produce diethyl carbonate.

Definition

ChEBI: Diethyl carbonate is a carbonate ester.

Application

Diethyl carbonate is a well-known linear organic carbonate that has wide applications. It is an active component of electrolytes used in lithium which is used as a solvent for cellulose ethers, nitro cellulose, manufacture of radio tubes, fixing rare earths to cathode elements, natural and synthetic resin and in erythromycin intramuscular injections. It is also used in the synthesis of 3-ethyl-4-methyl-5-phenyl-3H-oxazol-2-one, phenobarbital, pyrethrum batteries.

Preparation

Diethyl carbonate is prepared by reaction of phosgene and ethyl alcohol to produce ethyl chlorocarbonate followed by reaction with anhydrous ethylalcohol at elevated temperatures. direct synthesis of diethyl carbonate (dec) by carboxylation of ethanol with co2 was investigated over ceria catalysts.

Synthesis Reference(s)

Journal of the American Chemical Society, 104, p. 1769, 1982 DOI: 10.1021/ja00370a068

General Description

Diethyl carbonate appears as a colorless liquid with a mild pleasant odor. It is slightly less dense than water and insoluble in water.

Air & Water Reactions

Highly flammable. Insoluble in water.

Reactivity Profile

Diethyl carbonate reacts with acids to liberate heat along with ethanol and carbon dioxide. Strong oxidizing acids may cause a vigorous reaction that is sufficiently exothermic to ignite the reaction products. Heat is also generated by the interaction with caustic solutions. Flammable hydrogen is generated by mixing with alkali metals and hydrides.

Health Hazard

High vapor concentrations can cause headache, irritation of eyes and respiratory tract, dizziness, nausea, weakness, loss of consciousness.

Flammability and Explosibility

Flammable

Safety Profile

Wdly toxic by subcutaneous route. Questionable carcinogen with experimental tumorigenic and teratogenic data. A dangerous fire hazard when exposed to heat or flame; can react with oxidizing materials. To fight fire, use foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and fumes. See also ANHYDRIDES.

Carcinogenicity

A study using male and female mice treated with 0, 50, 250, or 1000 ppm (0–140 mg/kg/day) diethyl carbonate in drinking water indicated no carcinogenic effects.

Purification Methods

Wash the ester (100mL) with an aqueous 10% Na2CO3 (20mL) solution, saturated CaCl2 (20mL), then water (30mL). After drying by standing over solid CaCl2 for 1hour (note that prolonged contact should be avoided because slow combination with CaCl2 occurs), it should be fractionally distilled. Also dry it over MgSO4 and distil it. [Beilstein 3 H 5, 3 I 4, 3 II 4, 3 III 5, 3 IV 5.]