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.[3] This colorless and odorless liquid is useful as a polar, aprotic solvent.[4] Propylene carbonate is chiral, but is used as the racemic mixture in most contexts.

Propylene carbonate[1][2]

Names
IUPAC name 4-Methyl-1,3-dioxolan-2-one
Other names (R,S)-4-Methyl-1,3-dioxolan-2-one Cyclic propylene carbonate Carbonic acid propylene ester Cyclic 1,2-propylene carbonate Propylene glycol cyclic carbonate 1,2-Propanediol carbonate 4-Methyl-2-oxo-1,3-dioxolane Arconate 5000 Texacar PC
Identifiers
CAS Number	108-32-7
3D model (JSmol)	Interactive image
ChemSpider	7636
ECHA InfoCard	100.003.248
PubChem CID	7924
UNII	8D08K3S51E
CompTox Dashboard (EPA)	DTXSID2026789
InChI InChI=1S/C5H8O6/c1-3(11-5(8)9)2-10-4(6)7/h3H,2H2,1H3,(H,6,7)(H,8,9)/p-1 Key: ZEBXBLIKXVICMJ-UHFFFAOYSA-M InChI=1/C5H8O6/c1-3(11-5(8)9)2-10-4(6)7/h3H,2H2,1H3,(H,6,7)(H,8,9)/p-1 Key: ZEBXBLIKXVICMJ-REWHXWOFAP
SMILES CC1COC(=O)O1
Properties
Chemical formula	C4H6O3
Molar mass	102.089 g·mol^−1
Appearance	Colorless liquid
Density	1.205 g/cm^3
Melting point	−48.8 °C (−55.8 °F; 224.3 K)
Boiling point	242 °C (468 °F; 515 K)
Solubility in water	Very soluble (240 g/L at 20°C)
Refractive index (nD)	1.4189
Structure
Dipole moment	4.9 D
Hazards
Main hazards	Xi
Safety data sheet	MSDS by Mallinckrodt Baker
R-phrases (outdated)	R36
S-phrases (outdated)	S26 S36
NFPA 704 (fire diamond)	1 1 1
Flash point	132 °C (270 °F; 405 K)
Autoignition temperature	455 °C (851 °F; 728 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Although many organic carbonates are produced using phosgene, propylene and ethylene carbonates are exceptions. They are mainly prepared by the carbonation of the epoxides[4] (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 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.[5]

Applications

As a solvent

Propylene carbonate is used as a polar, aprotic solvent.[6] 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).[1] 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.[7]

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.[8]

Propylene carbonate can also be found in some adhesives, paint strippers, and in cosmetics.[9] 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.[10]

Other

Propylene carbonate product may be converted to other carbonate esters by transesterification as well (see Carbonate ester#Carbonate transesterification).[4]

In electrospray ionization mass spectrometry, propylene carbonate is doped into low surface tension solutions to increase analyte charging.[11]

In Grignard reaction propylene carbonate (or most other carbonate esters) might be used to create tertiary alcohols.

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.[12] 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.[13]

See also

• Ethylene carbonate
• Trimethylene carbonate

References

1. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. ISBN 1439855110.
2. Propylene carbonate at Sigma-Aldrich.
3. WebBook page for propylene carbonate.
4. Hans-Josef Buysch. "Carbonic Esters". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_197..
5. Synthesis of propylene carbonate from urea http://pubs.acs.org/doi/abs/10.1021/ie049948i
6. Dieter Stoye. "Solvents". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_437..
7. J. Jorné; C. W. Tobias (1975). "Electrodeposition of the alkali metals from propylene carbonate". J. Appl. Electrochem. 5 (4): 279–290. doi:10.1007/BF00608791. S2CID 93629501.
8. Doron Aurbach (1999). Nonaqueous Electrochemistry. CRC Press. ISBN 978-0824773342.
9. Record in the Household Products Database of NLM.
10. Schendel, R. "Comparison of Fluor Solvent and Selexol Processes" (PDF). Retrieved 4 April 2016.
11. Teo C. A., Donald W. A. (May 2014). "Solution additives for supercharging proteins beyond the theoretical maximum proton-transfer limit in electrospray ionization mass spectrometry". Anal. Chem. 86 (9): 4455–62. doi:10.1021/ac500304r. PMID 24712886.
12. "Environmental Profile for Propylene Carbonate". U.S. Environmental Protection Agency. 1998.
13. Johnson, William L. "REVISION TO DEFINITION OF VOLATILE ORGANIC COMPOUNDS - EXCLUSION OF PROPYLENE CARBONATE AND DIMETHYL CARBONATE". US Environmental Protection Agency. US EPA. Retrieved 11 July 2015.