Solvents dimethyl carbonate

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 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. 

The alkali-catalysed methanolysis of poly(2,2-bis(4-hydroxyphenyljpropane carbonate) (PC) in a mixture of methanol (MeOH) and toluene or dioxane was studied. The treatment of PC in meOH, with a catalytic amount of sodium hydroxide, yielded only 7% bisphenol A. Using a mixed solvent of MeOH and toluene completely depolymerised PC to give 96% free bisphenol A in solid form and dimethyl carbonate in solution. The eharaeteristies of the catalysis are discussed together with the pseudo-first rate kinetics of the depolymerisation. The reaetion eonditions were investigated to facilitate the reeyeling of PC plasties. 17 refs. 

Currently, graphite-based lithium ion batteries use mixed solvent electrolytes containing highly viscous ethylene carbonate (EC) and low viscosity dilutants such as dimethyl carbonate (DMC) or diethyl carbonate (DEC) as main solvents. EC is indispensable because of its excellent filming characteristics. DMC and/or DEC are required to get the low temperature... 

Current single-mode continuous-flow microwave reactors allow the processing of comparatively small volumes. Much larger volumes can be processed in continuous-flow reactors that are housed inside a multimode microwave system. In a 2001 publication, Shieh and coworkers described the methylation of phenols, indoles, and benzimidazoles with dimethyl carbonate under continuous-flow microwave conditions using a Milestone ETHOS-CFR reactor (see Fig. 3.11) [104]. In a typical procedure, a solution containing the substrate, dimethyl carbonate, 1,8-diazabicy-clo[5.4.0]undec-7-ene (DBU) base, tetrabutylammonium iodide (TBAI), and a solvent was circulated by a pump through the microwave reactor, which was preheated to 160 °C and 20 bar by microwave irradiation (Scheme 4.31). Under these condi-... 

A potential green route to dimethyltin carbonate can be based on the reaction of methanol and carbon dioxide, catalyzed by dimethyltin dimethoxide. In supercritical CO2 as solvent, the dimethoxide reacts to give the monocarbonate, which at 180 °C and 300 atm pressure gives dimethyl carbonate, probably by an intramolecular rearrangement, with regeneration of the dimethoxide (Equation (139)).385,386... 

Electrolyte solutions of various aprotic organic solvents are used in primary lithium batteries. Among the organic solvents are alkyl carbonates [PC (er = 64.4-), ethylene carbonate (EC, 89.640°c)> dimethyl carbonate (DMC, 3.1), diethyl carbonate (DEC, 2.8)], ethers [DME (7.2), tetrahydrofuran (THF, 7.4), 2-Me-THF (6.2),... 

Aresta and Quaranta studied the reactivity of alkylammonium N-alkylcarbamates (RNH3)02CNHR towards a different acylating substrate, such as dimethyl carbonate (DMC) [62a, b]. Carbamate salts (RNH3)02CNHR (R = benzyl, allyl, cyclohexyl), prepared in situ from aliphatic primary amines and C02, reacted with DMC to afford N-alkyl methylcarbamates (Equation 6.6). The reaction requires mild conditions (343-363 K 0.1 MPa C02 pressure) and can be carried out in DMC used as solvent and reagent. At 363 K, carbamate esters were obtained in satisfactory yield (45-92%) with high selectivity, as side products such as ureas, N,N-dialkylcarbamate esters, and alkylated amines were formed in very small amounts. 

For example, the ratio of ene products 71a/71b decreases by a factor of 5 in going from carbon tetrachloride to the most polar solvent, dimethyl sulfoxide (DMSO). 

Freshly prepared sodium methoxide (0.1 ml of a 1 M solution in methanol, 10 mmol) was added dropwise to a solution of cis-3,5-cyclohexadiene-l,2-diol (112 mg, 1 mmol) in dimethyl carbonate (1.7 ml) and methanol (0.2 ml) at RT under argon, and stirred for 20 min. A small aliquot was removed, solvent evaporated in vacuum (bath T 22°C) and the resulting solid was washed with a small volume of chilled (-20°C) ether and chilled (-20°C) petrol (b.p. 30°-40°C) to afford the 3a,7a-dihydrobenzo[l,3]dioxol-2-one (cyclic carbonate) as a beige-coloured solid, mp 90°C (dec.). 

The ene-yne CM of fatty acid-derived terminal alkenes with several alkyne derivatives was shown by Bruneau et al. [75], These reactions, which led to renewable conjugated dienes, were performed in a one-pot two-step procedure. In the first step, the ethenolysis of methyl oleate was performed in the presence of the first-generation Hoveyda-Grubbs catalyst (2.5 mol%) using dimethyl carbonate as solvent at room temperature. After completion of the ethenolysis (90% conversion), C4 (1 mol%) and the corresponding alkyne (0.5 equivalents with respect to olefins) were added and the reaction was run at 40°C for 2 h (Scheme 9). The desired dienes were thus obtained in high yields close to the maximum theoretical value (50%). Moreover, in order to maximize the formation of functional dienes, the same reaction sequence was applied to the diester obtained by SM of methyl oleate. In this way, the yield of functional dienes was increased up to 90% depending on the... 

As already mentioned, salt-containing liquid solvents are typically used as electrolytes. The most prominent example is LiPF6 as a conductive salt, dissolved in a 1 1 mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) as 1 molar solution. It should be mentioned that this electrolyte is not thermodynamically stable in contact with lithium or, for example, LiC6. Its success comes from the fact that it forms an extremely stable passivation layer on top of the electrode, the so-called solid-electrolyte interface (SEI) [35], Key properties of such SEI layers are high Li+ and very low e conductivity - that is, they act as additional electrolyte films, where the electrode potential drops to a level the liquid electrolyte can withstand [36],... 

Electrolyte solvent Aprotic solvent Propylene carbonate, Diethyl carbonate, Dimethyl carbonate, Dimethoxy ethane... 

Figure 4. Comparison of observed solvation times to predictions of the SC and DMSA theories. The points show the comparison between the DMSA theoiy for an ionic solute with polar aptotic solvents denoted by circles and associated solvents by squares. For clarity, the SC and DMSAd comparisons are only shown as the linear fits to the log-log data with the SC predictions being the lower dashed line and the DMSAd the uiqjer dashed line. The solvents represented here are, in order of increasing fj, acetonitrile, acetone, tetrahydrofiiran, dimethyl-formamide, dimethylsulfoxide, propylm carbonate, dimethyl carbonate, chloroform, and benzonitrile (circles) and water [16], formamide, methanol, ethylene glycol, ethanol, 1-propanol, l-pentanol, and 1-decanol (squares).

The Williamson reaction, discovered in 1850, is still the best general method for the preparation of unsymmetrical or symmetrical ethers.The reaction can also be carried out with aromatic R, although C-alkylation is sometimes a side reaction (see p. 515). The normal method involves treatment of the halide with alkoxide or aroxide ion prepared from an alcohol or phenol, although methylation using dimethyl carbonate has been reported. It is also possible to mix the halide and alcohol or phenol directly with CS2CO3 in acetonitrile, or with solid KOH in Me2SO. The reaction can also be carried out in a dry medium,on zeolite-or neat or in solvents using microwave irradiation. Williamson ether synthesis in ionic liquids has also been reported. The reaction is not successful for tertiary R (because of elimination), and low yields are often obtained with secondary R. Mono-ethers can be formed from diols and alkyl halides. Many other... 

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