Propylene carbonate (often abbreviated PC) is an organic compound with the formula C₄H₆O₃. It is a cyclic

carbonate ester In organic chemistry, a carbonate ester (organic carbonate or organocarbonate) is an ester of carbonic acid. This functional group consists of a carbonyl group flanked by two alkoxy groups. The general structure of these carbonates is and they ...

derived from

propylene glycol Propylene glycol ( IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two alcohol groups, it is classed as a diol. It is ...

. This colorless and odorless liquid is useful as a

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the cli ...

aprotic solvent A polar aprotic solvent is a solvent that lacks an acidic proton and is polar. Such solvents lack hydroxyl and amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Am ...

. Propylene carbonate is

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...

, but is used as the

racemic mixture In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

in most contexts.

Preparation

Although many organic carbonates are produced using

phosgene Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, esp ...

, propylene and ethylene carbonates are exceptions. They are mainly prepared by the

carbonation Carbonation is the chemical reaction of carbon dioxide to give carbonates, bicarbonates, and carbonic acid. In chemistry, the term is sometimes used in place of carboxylation, which refers to the formation of carboxylic acids. In inorganic ...

of the epoxides (epoxypropane, or propylene oxide here): :CH₃CHCH₂O + CO₂ → CH₃C₂H₃O₂CO 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 Propylene glycol (IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. Containing two alcohol groups, it is classed as a diol. It is ...

with phosgene is complex, yielding not only propylene carbonate but also oligomeric products. Propylene carbonate can also be synthesized from

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...

and

over

zinc acetate Zinc acetate is a salt with the formula Zn(CH3CO2)2, which commonly occurs as the dihydrate Zn(CH3CO2)2·2H2O. Both the hydrate and the anhydrous forms are colorless solids that are used as dietary supplements. When used as a food additive, it ha ...

Applications

As a solvent

Propylene carbonate is used as a polar,

aprotic A polar aprotic solvent is a solvent that lacks an acidic proton and is polar. Such solvents lack hydroxyl and amine groups. In contrast to protic solvents, these solvents do not serve as proton donors in hydrogen bonding In chemistry, a hydro ...

solvent. It has a high molecular dipole moment (4.9 D), considerably higher than those of

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscible wi ...

(2.91 D) and ethyl acetate (1.78 D). It is possible, for example, to obtain potassium, sodium, and other

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

s by

electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from na ...

of their

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...

s and other salts dissolved in propylene carbonate.

Electrolyte

Due to its high relative permittivity (dielectric constant) of 64, it is frequently used as a high- permittivity component of electrolytes in

lithium batteries Lithium battery may refer to: * Lithium metal battery, a non-rechargeable battery with lithium as an anode ** Rechargeable lithium metal battery, a rechargeable counterpart to the lithium metal battery * Lithium-ion battery, a rechargeable batt ...

, 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

adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...

paint stripper Paint stripper, or paint remover, is a chemical product designed to remove paint, finishes, and coatings, while also cleaning the underlying surface. The product's material safety data sheet provides more safety information than its product l ...

s, and in

cosmetics Cosmetics are constituted mixtures of chemical compounds derived from either natural sources, or synthetically created ones. Cosmetics have various purposes. Those designed for personal care and skin care can be used to cleanse or protect ...

. 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.

Other

Propylene carbonate product may be converted to other carbonate esters by transesterification as well (see Carbonate ester#Carbonate transesterification).. In

electrospray ionization Electrospray ionization (ESI) is a technique used in mass spectrometry to produce ions using an electrospray in which a high voltage is applied to a liquid to create an aerosol. It is especially useful in producing ions from macromolecules becaus ...

mass spectrometry, propylene carbonate is doped into low surface tension solutions to increase analyte charging. In

Grignard reaction The Grignard reaction () is an organometallic chemical reaction in which alkyl, allyl, vinyl, or aryl-magnesium halides (Grignard reagent) is added to a carbonyl group in an aldehyde or ketone. This reaction is important for the formation of ...

propylene carbonate (or most other carbonate esters) might be used to create

tertiary alcohol In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...

Safety

Clinical studies indicate that propylene carbonate does not cause skin irritation or sensitization when used in cosmetic preparations, whereas moderate skin irritation is observed when used undiluted. No significant toxic effects were observed in rats fed propylene carbonate, exposed to the vapor, or exposed to the undiluted liquid. In the US, propylene carbonate is not regulated as a volatile organic compound (VOC) because it does not contribute significantly to the formation of smog and because its vapor is not known or suspected to cause cancer or other toxic effects.

References

{{Authority control Ester solvents Plasticizers Carbonate esters