Molecular Modelling in Chromatostructural Analysis: A New Approach to the GC/MS Study of Isomers

Abstract

The importance of gas-solid chromatography as a source of additional data for the positive structural elucidation of novel isomers by gas chromatography/mass spectrometry is discussed. As an example, a mixture of 11 isomers of perhydroanthracene and perhydrophenanthrene has been considered. The retention parameters of these isomers on thermally graphitized carbon black (TGCB) were calculated by Kiselev's method to predict the order of their separation on a column packed with TGCB. The molecular models required for these calculations were constructed using a conventional approach and molecular mechanics; the corresponding results obtained are compared. The order of separation predicted by molecular mechanics appeared close to that observed experimentally.

The use of molecular-statistical methods for the calculation of thermodynamic characteristics of adsorption for identification of organic compounds by gas chromatography–mass spectrometry

“…This procedure has been used to predict the retention values for perhydroanthracenes and perhydrophenanthrenes. 51 By using this variation, the researchers predicted the order of isomer elution from a GTCB column that coincided with the experimental results. However, the geometry variation, especially for molecules with an unknown structure, is legitimate only in the case of quantitative comparison of theoretical and experimental data, and, naturally, it is impossible to estimate the variation of the AAP parameters in terms of this method.…”

“…49 The AAPs determined in this way were used to predict the TCA for a number of hydrocarbons and their derivatives, which are in good agreement with experimental data. 36,38,46 However, for many molecules [both relatively simple ones such as ortho-halobenzenes, 50 perhydroanthracenes, perhydrophenanthrenes, 51 heterocyclic nitrogen-containing compounds, 52,53 and fairly complex molecules such as molecules with abnormal geometric parameters (strained mole-cules), with bulky substituents, with several heteroatoms, and their unusual combinations], the TCA could not be correctly predicted.…”

Gas chromatography–mass spectrometry of the stereoisomers of heterocyclic compounds. Part 2a.1 Perhydroxanthenes

“…Now it is possible to solve this problem by the quantitative calculation of the retention order of novel adsorbates using the approach published recently. 11 The results of the application of this new quantitative concept to the further structural elucidation of the stereoisomers of PHX will be presented in the next paper of this series.…”

Gas chromatography–mass spectrometry of the stereoisomers of heterocyclic compounds. Part 3.† Perhydro-4-thia-s-indacene

“…As previously 6,7 it was determined by molecular-statistical calculations of the adsorption equilibrium constants (Henry constants, K 1 ) of isomers using Kiselev's method. [10][11][12] The atomic coordinates of adsorbate molecules, required by this method, were obtained after energy minimization of their hypothetical structures by molecular mechanics according to the approach successfully tried out earlier. 6,7,12 This results in plots of the dependence of ln K 1 on the reciprocal temperature 1/T which are shown in Fig.…”

“…[10][11][12] The atomic coordinates of adsorbate molecules, required by this method, were obtained after energy minimization of their hypothetical structures by molecular mechanics according to the approach successfully tried out earlier. 6,7,12 This results in plots of the dependence of ln K 1 on the reciprocal temperature 1/T which are shown in Fig. 4.…”