In Situ Formation of Alkylcarbonic Acis with CO_2

摘要

The mutual solubility of carbon dioxide and alcohols over a wide range of temperature and pressure provides a useful and tunable medium for reactions and separations. For many years, researchers have used alcohols as cosolvents in supercritical CO_2, and recently CO_2-swollen alcohols have been used for antisolvent crystallization and as mobile phases for chromatography. However, little consideration has been given to chemical interaction between the alcohols and CO_2. We have confmned that such an interaction does exist and can create an acidic environment. By isolating reaction products we have demonstrated that alcohol- CO_2 complexes react similarly to carboxylic acids with diazodiphenylmethane, a compound typically used to evaluate acid strengths. Our evidence indicates that the behavior of CO_2-alcohol systems is comparable to that of CO_2-water systems, where carbonic acid is formed.