Mutual correlation between gas chromatographic retention indices of unsaturated and saturated hydrocarbons found by molecular dynamics

It is shown that gas chromatographic retention indices for cycloalkenes can be calculated from the corresponding data for cycloalkanes (and vice versa ) using computer simulation of intramolecular vibrational and rotational pr ocesses by molecular dynamics. For organic compounds structurally related a s A --> B, the total internal energy differences Delta E = E(B) - E(A) corr elate with the corresponding differences in retention indices Delta I = I(B ) - I(A), and a linear relationship exists Delta I = a Delta E + b (a < 0, \p\ > 0.9). Limitations are found for the use of molecular dynamics for com pounds having n-alkyl radicals with no less than four carbon atoms. In thes e cases, a simpler model for the evaluation of dynamic molecular parameters should be preferred for the calculation of retention indices of acyclic al kenes and alkanes. The reliability of the retention indices evaluated by th e proposed technique is comparable to their interlaboratory reproducibility found using standard nonpolar poly(dimethylsiloxane) stationary phases.