Simplification of the CBS‐QB3 method for predicting gas‐phase deprotonation free energies

Simplified versions of CBS-QB3 model chemistry were used to calculate the free energies of 36 deprotonation reactions in the gas phase. The best such version, S9, excluded coupled cluster calculation (CCSD(T)), and empirical (Eemp) and spin- orbit (Eint) correction terms. The mean absolute deviation and root mean square thus obtained (viz. 1.24 and 1.56 kcal/mol, respectively) were very-close to those provided by the original CBS-QB3 method (1.19 and 1.52 kcal/mol, respectively). The high- accuracy of the proposed simplification and its computational expeditiousness make it an excellent choice for energy calculations on gas-phase deprotonation reactions in complex systems. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem 110: 323-330, 2010

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