X-Ray Diffraction and Computer Simulation Studies of the Structure of Liquid Aliphatic Aldehydes: From Propanal to Nonanal

Synchrotron X-ray diffraction experiments and molecular dynamics (MD) simulations have been performed on simple aliphatic aldehydes, from propanal to nonanal. The performance of the OPLS (Optimized Potentials for Liquid Simulations) all-atom interaction potential model for aldehydes has been assessed via direct comparison of simulated and experimental total scattering structure factors. In general, MD results reproduce the experimental data at least semi-quantitatively. However, a slight mismatch can be observed between the two datasets in terms of the position of the main diffraction maxima. Partial radial distribution functions have also been calculated from the simulation results. Clear differences can be detected between the various O-H partial radial distribution functions, depending on whether the H atom is attached to the carbon atom that is doubly bonded to the oxygen atom of the aldehyde group or not.