Dimethyl-carbonate

The conventional electrochemical reduction of carbon dioxide tends to give formic acid as the major product, which can be obtained with a 90% current efficiency using, for example, indium, tin, or mercury cathodes. Being able to convert CO2 initially to formates or formaldehyde is in itself significant. In our direct oxidation liquid feed fuel cell, varied oxygenates such as formaldehyde, formic acid and methyl formate, dimethoxymethane, trimethoxymethane, trioxane, and dimethyl carbonate are all useful fuels. At the same time, they can also be readily reduced further to methyl alcohol by varied chemical or enzymatic processes. 

CycHc carbonates are made by treating 1,2-diols with dialkyl carbonates using an alkyl ammonium and tertiary amine catalyst. The combination of propylene glycol and dimethyl carbonate has been reported to result in a 98% yield of propylene carbonate (21). 

Phenyl-3,6-dihydro-l,3,4-oxadiazin-2-one (50) is a high temperature blowing agent used primarily for polycarbonates (qv). It is prepared by the reaction of a-hydroxyacetophenone and methyl carbazate (52), made from hydrazine and dimethyl carbonate (175) ... 

Both dimethyl carbonate [616-38-6] and diphenyl carbonate [102-09-0] have been used, in place of carbon monoxide, as reagents for the conversion of amines into isocyanates via this route (28,29). Alternatively, aniline [62-53-3] toluene diamines (I JJA), and methylene dianilines (MDA) have also been used as starting materials in the carbonylations to provide a wide variety of isocyanate monomers. 

Other approaches have explored the reaction of amines with dimethyl carbonate or its precursors (28). A reaction scheme for the production of polymeric MDI is as follows ... 

An analogue of the transesterification process has also been demonstrated, in which the diacetate of BPA is transesterified with dimethyl carbonate, producing polycarbonate and methyl acetate (33). Removal of the methyl acetate from the equihbrium drives the reaction to completion. Methanol carbonylation, transesterification using phenol to diphenyl carbonate, and polymerization using BPA is commercially viable. The GE plant is the first to produce polycarbonate via a solventiess and phosgene-free process. 

As seen in Figure 1, the organo sulfur compounds are methylated at the boiling point (90°C) of dimethyl carbonate, whereas methylation (or alkylation with other alkyl groups) of other functional groups requites higher temperatures. This has resulted in the selective methylation of sulfhydryl groups of compounds that contain other substituents that can be alkylated. The other substituents can then be alkylated at elevated temperatures (63). 

Unlike chloroformates, diethyl and dimethyl carbonates are only mildly irritating to the eyes, skin, and mucous membranes. Diethylene glycol bis(aHyl carbonate) may be irritating to the skin, but it is not classified as a toxic substance however, it is extremely irritating to the eyes. 

Dimethyl carbonate [616-38-6] and dimethyl oxalate [553-90-2] are both obtained from carbon monoxide, oxygen, and methanol at 363 K and 10 MPa (100 atm) or less. The choice of catalyst is critical cuprous chloride (66) gives the carbonate (eq. 20) a palladium chloride—copper chloride mixture (67,68) gives the oxalate, (eq. 21). Anhydrous conditions should be maintained by removing product water to minimize the formation of by-product carbon dioxide. 

Oxygenates and Chemicals A whole host of oxygenated products, i.e., fuels, fuel additives, and chemicals, can be produced from synthesis gas. These include such produc ts as methanol, ethylene, isobutanol, dimethyl ether, dimethyl carbonate, and many other hydrocarbons and oxyhydrocarbons. Typical oxygenate-producing reactions are ... 

Dimethyl carbonate is available from Aldrich Chemical Company, Inc. The checkers dried the tetrahydrofuran Immediately before use by distillation from the sodium ketyl of benzophenone under a nitrogen atmosphere. The submitters purchased sodium hydride (50% oil dispersion) from Alfa Products, Morton/Thiokol, Inc. The checkers used 12.24 g of a 50% dispersion of sodium hydride in mineral oil obtained from the same supplier. The dispersion was washed with three portions of pentane to remove the mineral oil and the remaining sodium hydride was allowed to dry under nitrogen. 

Dimethyl carbonate Carbonic acid, dimethyl ester (8,9) (615-38-6)... 

Dimethyl carbonate [616-38-5] M 90.1, m 4.65", b 90-91", d 1.070, n 1.369. Contains small amounts of water and alcohol which form azeotropes. Stood for several days in contact with Linde type 4A molecular sieves, then fractionally distd. The middle fraction was frozen slowly at 2°, several times, retaining 80% of the solvent at each cycle. 

Dimethyl sulfate (16 g) is added to a mixture of dimethyl carbonate (400 g) and deuterium oxide (1(X) g) in a 1 liter flask. Two reflux condensers and a drying tube are attached in series (initial rapid evolution of carbon dioxide may entrain some liquid), and the reaction mixture is heated under reflux for 72 hr. The methanol-OD is distilled directly from the reaction flask through a 30 cm Vigreux column. Redistillation from a small amount of sodium yields 275 g of pure methanol-OD bp 66-66.5° isotopic purity, 98.6%. ... 

Dimethyl carbonate, (Bu2N)2C=NMe, 180°, 4.5 h, 54-99% yield. In the presence of this guanidine, aromatic methyl carbonates are converted to methyl ethers with loss of CO2. 

For primary aromatic amines dimethyl carbonate, Y-Zeolite, 130-150°, 72-93% yields. ... 

A solution of 0.1 mol of each of thiophene-2-carboxaldehyde and 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine in dimethyl carbonate (0.2 mol) is held at 27°C for 48 hours. The reaction mixture is then stripped to give a 65% yield of product as the free base. 

Dimethyl carbonate (DMC) is a colorless liquid with a pleasant odor. It is soluble in most organic solvents but insoluble in water. The classical synthesis of DMC is the reaction of methanol with phosgene. Because phosgene is toxic, a non-phosgene-route may be preferred. The new route reacts methanol with urea over a tin catalyst. However, the yield is low. Using electron donor solvents such as trimethylene glycol dimethyl ether and continually distilling off the product increases the yield. ... 

Dimethyl carbonate is used as a specialty solvent. It could be used as an oxygenate to replace MTBE. It has almost three times the oxygen content as MTBE. It has also a high octane rating. However, it must be evaluated in regard to economics and toxicity. 

Ethylene carbonate is a reactive chemical. It reacts smoothly with methanol and produces ethylene glycol in addition to dimethyl carbonate ... 

Diphenol carbonate is produced by the reaction of phosgene and phenol. A new approach to diphenol carbonate and non-phosgene route is by the reaction of CO and methyl nitrite using Pd/alumina. Dimethyl carbonate is formed which is further reacted with phenol in presence of tetraphenox titanium catalyst. Decarbonylation in the liquid phase yields diphenyl carbonate. 

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