Monte Carlo Studies of the Aqueous Hydration of cis‐ and trans‐ N‐ Methyl‐Acetamide: Sensitivity of Results to Convergence and to Choice of Intermolecular Potential Functions

A series of liquid state Monte Carlo computer simulations on the N‐methyl acetamide in water (NMA molecule) are described, considering both the cis and trans isomeric forms of NMA. Two independent sets of calculations were performed, one set based on the potential functions developed by Clementi and co‐workers (CPF) used in conjunction with the Matsuoka et al. (MCY) water‐water potential, and the other set using the OPLS potential of Jorgensen and coworkers for solute‐water interactions and the TIP4P potential for the water‐water interactions. The relative hydration energies of the cis and trans isomers of NMA and the transfer energies of NMA from free space to water are discussed with respect to the convergence level of the simulations and the sensitivity of results to the choice of the intermolecular potential functions. The structural chemistry of the aqueous hydration for NMA is developed from the simulation result based on Proximity Analysis. The sensitivity of the structural and energetic indices of analysis to choice of potential is described. Preliminary results of the calculation of the hydration contribution to the free energy are also presented.