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Accuracy of free energies of hydration for organic molecules from 6‐31g*‐derived partial charges
Author(s) -
Carlson Heather A.,
Nguyen Toan B.,
Orozco Modesto,
Jorgensen William L.
Publication year - 1993
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540141013
Subject(s) - chemistry , mulliken population analysis , partial charge , molecule , ab initio , computational chemistry , thermodynamics , physics , organic chemistry
Abstract Absolute free energies of hydration have been computed for 13 diverse organic molecules using partial charges derived from ab initio 6‐31G* wave functions. Both Mulliken charges and charges fit to the electrostatic potential surface (EPS) were considered in conjunction with OPLS Lennard–Jones parameters for the organic molecules and the TIP4P model of water. Monte Carlo simulations with statistical perturbation theory yielded relative free energies of hydration. These were converted to absolute quantities through perturbations to reference molecules for which absolute free energies of hydration had been obtained previously in TIP4P water. The average errors in the computed absolute free energies of hydration are 1.1 kcal/mol for the 6‐31G* EPS charges and 4.0 kcal/mol for the Mulliken charges. For the EPS charges, the largest individual errors are under 2 kcal/mol except for acetamide, in which case the error is 3.7 kcal/mol. The hydrogen bonding between the organic solutes and water has also been characterized. © John Wiley & Sons, Inc.