In situ formation of alkylcarbonic acids with CO2

The mutual solubility of carbon dioxide and alcohols over a wide range of t emperature and pressure provides a useful and tunable medium for reactions and separations. For many years, researchers have used alcohols as cosolven ts in supercritical CO2, and recently CO2-swollen alcohols have been used f or antisolvent crystallization and as mobile phases for chromatography. How ever, little consideration has been given to chemical interaction between t he alcohols and CO2. We have confirmed that such an interaction does exist and can create an acidic environment. By isolating reaction products we hav e demonstrated that alcohol-CO2 complexes react similarly to carboxylic aci ds with diazodiphenylmethane, a compound typically used to evaluate acid st rengths. Our evidence indicates that the behavior of CO2-alcohol systems is comparable to that of CO2-water systems, where carbonic acid is formed.