MOLECULAR-DYNAMICS OF PARAFFINS IN THE NORMAL-ALKANE UREA CLATHRATE

Simulations of the molecular dynamics of n-CNH2N+2 in the n-alkane/urea clathrate have been performed for N = 13,23,33, for a period of 1 ns. Parallel simulations were performed starting from conformations in which all CH2-CH2 bonds were in the trans conformation, and starting from a conformation in which one of the terminal CH2-CH2 bonds was in a gauche conformation. These simulations suggest less than 3% of the terminal CH2-CH2 bonds would be in a gauche state at equilibrium. The gauche content is much smaller at the CH2-CH2 bonds further removed from the ends of the chain. No significant differences are seen in the simulations performed with n-alkanes with N = 13,23,33. The mobility of the C-H bond vectors about the axis defined by the channel is greater at the ends than in the middle of the chain. The angular distribution is nearly randomized in 1 ns-for the C-H vector in a methyl group, but a longer time scale would be required for randomization of this distribution for the C-H vector bonded to the central methylene group in C33H68.