Molecular Dynamics Simulation of Infinite Dilution Diffusion and Local Structure of Eight n-Alkanols in 1-Octanol

The diffusion and local structure of eight normal alkanols in 1-octanol at infinite dilution from 298 to 370 K have been investigated via molecular dynamics simulation. For short-chain n-alkanols, the simulated infinite dilute diffusion coefficients D12 are in good agreement with the experimental data, while for long-chain n-alkanols, the simulated D12 overestimate the experimental data. Meanwhile, the local structures are characterized by calculating the radial distribution functions, hydrogen bond, radius of gyration, and end-to-end distance. It is interesting that the average number of hydrogen bonds decreases as the chain length of n-alkanols increases from methanol to 1-heptanol, but unexpectedly, the average number of hydrogen bonds for 1-nonanol begins to increase. The simulation results demonstrate that a kind of intertwist effect through alkyl chain-chain interactions and caused by the molecular flexibility could explain the abnormal change of hydrogen bond number and the serious overestimation of simulated D12 for long-chain n-alkanols.