Propylene carbonate (often abbreviated PC) is an organic compound with the formula CH3C2H3O2CO [1]. It is a polar aprotic substance with very similar physicochemical characteristics to the organic solvents traditionally used for organic synthesis, such as acetonitrile and acetone. Therefore, PC is beginning to be used as a “green” sustainable alternative solvent for chemical transformations. PC can be prepared by a reaction between propylene epoxide and carbon dioxide with 100% atomic economy. The easy preparation of propylene epoxide and the use of an available, abundant, economical, and renewable source of carbon, such as CO2, make this process one of the best routes for the synthesis of PC. PC is a low toxicity, non-corrosive colourless liquid with a high boiling point and low vapour pressure. It is biodegradable and economical, allowing its large-scale use [2].

Properties of Propylene Carbonate

PC is a polar, aprotic solvent that has been used as an electrolyte in lithium batteries, a polymeric precursor (e.g., in polycarbonates), in cosmetics, and as an intermediary in the production of pharmaceutical and chemical products (e.g., dialkyl carbonates, glycols, carbamates, pyrimidines, purines).

Currently, PC is beginning to be used as a “green” sustainable solvent alternative for chemical transformations. PC is a colourless, non-corrosive liquid of low toxicity with a high boiling point and low vapour pressure. It is biodegradable and economical, which allows its large-scale use.

Preparation of Propylene Carbonate

Because of the great current interest in organic carbonates, different synthesis methods are being developed for their production. Among these methods is the treatment of aldehydes with sulphur ylide in the presence of CO2, the reaction of CO2 with propylene glycol, the oxidative carboxylation of diols, the reduction of ethyl lactate followed by direct intramolecular displacement, and the reaction between urea and 1,2-propylene glycol catalysed by zinc acetate.

PC can be prepared by a reaction between propylene epoxide and carbon dioxide with 100% atomic economy. The easy preparation of propylene epoxide and the use of a renewable, available, abundant, and economical source of carbon, such as CO2, make this process one of the best ways to synthesise PC. Additionally, it is estimated that during the 21st century, CO2 emissions will be between 3480 and 8050 Gt. Hence, this reaction is interesting because of the fixation of CO2 from the atmosphere. For this reason, numerous catalytic systems have been developed to improve the efficiency of this reaction [2].

Benefits of Propylene Carbonate

In the context of Green Chemistry, processes that minimise environmental impact are of great interest at both the industrial and academic levels, and the use of solvents that are innocuous to the environment is also a factor of great interest. Propylene carbonate maybe an appropriate choice. Not only it has a low evaporation rate, low toxicity, and VOC exemption, PC also has other benefits such as:

• Improves lubricity
• It is chemically stable
• Co-firing in any atmosphere without oxidation
• Excellent viscosity properties and green strength
• Propylene Carbonate is one of the most eco-efficient alternatives for coating wires [3].

Reference

[1] https://encyclopedia.thefreedictionary.com/Propylene+carbonate
[2] S. Bello Forero Josué, et al. "Propylene Carbonate in Organic Synthesis: Exploring its Potential as a Green Solvent." Current Organic Synthesis 13.6(2016):834-846.
[3] https://ecolink.com/info/uses-and-benefits-of-propylene-carbonate/