Ab initioMO calculations on the acidities of water and methanol, and hydrogen bond energies of the conjugate ions with a water molecule

✍ Scribed by Shigeru Ikuta

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 604 KB
• Volume: 5
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540050415

✦ Synopsis

The acidities, deprotonation energies, of water and methanol were calculated by the use of the ab initio self-consistent-field (SCF) molecular orbital (MO) method with electron correlation computed by the thirdorder Meller-Plesset perturbation method and configuration interaction with double excitations. Zero-point vibrational energy correction, translational energy change, and the PV work term were included to evaluate the accurate acidities. The calculated acidity difference including these corrections was 7 kcal/mol, which is somewhat smaller than the experimental ones (9.5-12.5 kcal/mol) recently determined. The hydrogen bond energies of the conjugate ions (OH-and CH,O-) with a water molecule were calculated to be 2.3 kcal/mol near the Hartree-Fock limit; this energy only amounts to 25% of the (total) hydration energy difference between the two negative ions. The aqueous solvation effect on the acidity scale was discussed.