Propylene carbonate

Propylene carbonate (often abbreviated PC) is an organic compound with the formula C4H6O3. It is a cyclic carbonate ester derived from propylene glycol. This colorless and odorless liquid is useful as a polar, aprotic solvent. Propylene carbonate is chiral, but is used exclusively as the racemic mixture in most contexts. Propylene carbonate (often abbreviated PC) is an organic compound with the formula C4H6O3. It is a cyclic carbonate ester derived from propylene glycol. This colorless and odorless liquid is useful as a polar, aprotic solvent. Propylene carbonate is chiral, but is used exclusively as the racemic mixture in most contexts. Although many organic carbonates are produced using phosgene, propylene and ethylene carbonates are exceptions. They are mainly prepared by the carbonation of the epoxides (epoxypropane, or propylene oxide here): The process is particularly attractive since the production of these epoxides consumes carbon dioxide. Thus this reaction is a good example of a green process. The corresponding reaction of 1,2-propanediol with phosgene is complex, yielding not only propylene carbonate but also oligomeric products. Propylene carbonate can also be synthesized from urea and propylene glycol over zinc acetate. Propylene carbonate is used as a polar, aprotic solvent. It has a high molecular dipole moment (4.9 D), considerably higher than those of acetone (2.91 D) and ethyl acetate (1.78 D). It is possible, for example, to obtain potassium, sodium, and other alkali metals by electrolysis of their chlorides and other salts dissolved in propylene carbonate. Due to its high dielectric constant of 64, it is frequently used as a high-permittivity component of electrolytes in lithium batteries, usually together with a low-viscosity solvent (e.g. dimethoxyethane). Its high polarity allows it to create an effective solvation shell around lithium ions, thereby creating a conductive electrolyte. However, it is not used in lithium-ion batteries due to its destructive effect on graphite. Propylene carbonate can also be found in some adhesives, paint strippers, and in cosmetics. It is also used as plasticizer. Propylene carbonate is also used as a solvent for removal of CO2 from natural gas and synthesis gas where H2S is not also present. This use was developed by El Paso Natural Gas Company and Fluor Corporation in the 1950s for use at the Terrell County Gas Plant in West Texas, now owned by Occidental Petroleum. Propylene carbonate product may be converted to other carbonate esters by transesterification as well (see Carbonate ester#Carbonate transesterification). In electrospray ionization mass spectrometry, propylene carbonate is doped into low surface tension solutions to increase analyte charging.