Photochemical fixation of supercritical carbon dioxide: the production of a carboxylic acid from a polyaromatic hydrocarbon

We present our initial results on the use of supercritical carbon dioxide as both a reactant and as a reaction medium to photo-chemically produce carboxylic acids from polycyclic aromatic hydrocarbons via radical anion intermediates. In the present work, we have found that photolysis of anthracene in supercritical carbon dioxide produces up to 57% yield of 9,10-dihydroanthracene-9-carboxylic acid in the presence of appropriate electron and hydrogen donors. This is in stark contrast to the lack of carboxylic acid formation in conventional non-polar aprotic solvents. Additionally, we have found no evidence that under reaction conditions similar to those necessary for radical anion fixation of carbon dioxide that carbon-centered free radicals produce carboxylic acids. (C) 2002 Elsevier Science Ltd. All rights reserved.