Reduced melting points also hasten chemical reactions. New research now demonstrates that dissolved carbon dioxide helps to melt the solid organic materials used to make medicines and so accelerates reactions. This could offer a cheaper 'green' route to some compounds.
Chemicals generally react faster in liquids than in solids.
So solid ingredients are usually dissolved in organic solvents before being used for industrial reactions, even though these solvents can be toxic and are a major source of chemical waste. Carbon dioxide is now making waves as an alternative, environmentally friendly solvent. At high pressures, the gas behaves as a so-called 'supercritical' fluid that dissolves reactants. But supercritical carbon dioxide requires a pressurized equipment and bespoke catalysts. This can make 'going green' an expensive, unattractive alternative.