Effects of methanol on the hydrogen bonding structure and dynamics in aqueous N-methylacetamide solution

The effect of methanol on the hydrogen bonding structure and dynamics in aqueous solution of N-methylacetamide (NMA) is investigated by classical molecular dynamics simulations. The modifications of structure and interaction between water and NMA in presence of methanol are calculated by different site-site radial distribution functions and average interaction energies between these species in the solution. It is observed that the methyl-methyl interaction between NMA and methanol prefers even at lower methanol concentration. The slower translational and rotational dynamics of NMA is observed in water-methanol mixtures as it is found for both water and methanol in the mixtures. The lifetime and structural-relaxation time of NMA-water and NMA-methanol hydrogen bonds show a strong increase with addition of methanol in the solution, whereas the change is not linearly dependent on concentration. It is also found that the lifetime of water-water and water-methanol hydrogen bond increases with increasing methanol concentration in the solution. (C) 2014 Elsevier B.V. All rights reserved.