A Diels-Alder reaction in supercritical water is studied by means of combin
ed electronic structure and liquid state theories. The target system is the
cycloaddition of cyclopentadiene with methyl vinyl ketone. The rate and th
e yield of the reaction in supercritical water are calculated and compared
with those in ambient water. The activation free energies of the two isomer
s, cis and trans, are compared. The results are in agreement with the exper
imentally observed increase of the rate and the yield. The solvation effect
for the rate constant is decreased in supercritical water, but the rate is
increased because of the thermal excitation rather than the solvation effe
ct. The trans-conformer has shown less activation energy in ambient water a
nd supercritical water compared to the cis-conformer. The estimated yield i
n supercritical water is more than 600 times higher than in ambient water.
The high yield in supercritical water is due to the high solubility of the
reactants to supercritical water.