Gas-phase and liquid-state properties of esters, nitriles, and nitro compounds with the OPLS-AA force field

Nonbonded and torsional parameters for carboxylate esters, nitriles, and ni tro compounds have been developed for the OPLS-AA force field. In addition, torsional parameters for alkanes have been updated. These parameters were fit to reproduce ab initio, gas-phase structures and conformational energet ics, experimental condensed-phase structural and thermodynamic properties, and experimental free energies of hydration. The computed densities, heats of vaporization, and heat capacities for fifteen liquids are in excellent a greement with experimental values. The new parameters permit accurate molec ular modeling of compounds containing a wider variety of functional groups, which are common in organic molecules and drugs. (C) 2001 John Wiley & Son s, Inc.