Pressure stabilization and solvation thermodynamics of a hemiketal reaction intermediate

This work reports the first pressure stabilization of a hemiketal intermedi ate, 2-methoxy-2 propanol, formed in the reaction of acetone and methanol, observed using Raman spectroscopy. Acetone dissolved in methanol is found t o under go a two-step reaction, with the ketal 2,2-dimethoxy-propane as the final product and the hemiketal observed as an intermediate. In a more dil ute stoichiometric mixture of acetone and methanol in liquid tetrahydrofura n (THF), quantitative formation of the hemiketal is observed at pressures a bove 2 GPa. The complete set of reaction thermodynamic functions (DeltaH de grees, DeltaV degrees, DeltaS degrees, DeltaG degrees, DeltaU degrees, Delt aA degrees) is obtained for the hemiketal formation reaction in THF as a fu nction of temperature and pressure and compared with previous measurements of DeltaH degrees, DeltaS degrees, and DeltaG degrees for acetone dissolved in methanol. Comparisons with quantum calculations for the isolated reacta nt and product species are used to completely quantitate the effects of sol vation on the hemiketal formation reaction.