Abstract
In the solvolysis of aspirin and acyl-α-chymotrypsin, the significant fact is the rate acceleration by the addition of alcohol in water solution. The authors reported that the rate acceleration of the hydrolysis occurs as the content of alcohol increases, since a water of the monomer state reacts with the ester part of aspirin or acyl-α-chymotrypsin. The mechanism was clarified by using nonempirical molecular orbital method. The proton removal energy for methanol corresponds to that for 1.4 waters. The difference of the proton removal energy between CH3OH and H2O is attributed to the electrostatic interaction term. On the other hand the main contributor for the difference between CH3OH and (H2O)2 is the polarization interaction term. Moreover the difference between H2O and (H2O)2 is due to the electrostatic interaction term. For the interaction energies between ester and hydroxyl ion and between ester and water, the charge transfer interaction term and the electrostatic interaction term, respectively, were significant.
