Solvent anions in supercritical carbon dioxide: Formation of complexes with polar solutes

It is shown that high-mobility multimer (CO2)(n)(.-) anions in supercritica l (sc)-CO2 form stable complexes with water, aliphatic alcohols, alkyl hali des, and alkyl nitriles. The complexation rate is 10-50% of the diffusion c ontrolled rate or faster. The complexes are formed both with the monomer an d with the dimer polar solutes. The equilibrium constants of the monomer co mplexation range from 10 to 350 M-1; the reaction heat is -(15-21) kJ/mol, and the reaction entropy is negative. The stability of the complex increase s with the dipole moment of the polar group and decreases with the substitu tion at the (x-carbon. None of these polar solutes directly reacts with qua sifree electrons in sc-CO2.