Elution volumes of thirty polycycloalkanes with adamantane and other structures were determined for gell chromatography on styrene-divinylbenzene gel in tetrahydrofuran. Elution volumes of methyl ethyladamantanes substituted on bridge heads can be determined on the basis of alkyl increments. In the series of polycycloalkanes of various structures a linear relationship between the distribution constants and effective molecular diameters has been established. A linear correlation has also been found between the elution volumes of isomeric tricycloalkanes and their relative enthalpies calculated from conformational analysis.Polycycloalkanes which constitute a considerable proportion of heavy mineral oil fractions are still little investigated because in consequence of the high number of existing isomers they represent the most complex structural class of hydrocarbons . occurring in petroleum. For the separation of complex hydrocarbon fractions of this type methods are advantageous that permit the separation of the mixtures on the basis of the size or the shape of the molecule. In our preceding papers 1 -3 in which we studied the methods of analysis of polycycloalkanes with adamantane structure we found two methods, viz. extractive crystallization with thiocarbamide 4 and thermodiffusion 5 , as suitable for the isolation of adamantane hydrocarbons from petroleum. In this paper we tested on model substances the method of gel chromatography for the separation of adamantan~ hydrocarbons.Gel chromatography was used originally predominantly for the separation of polymers and other macromolecules. Today, when gels with low exclusion limit are available gel chromatography may also be employed for the separation of smaller molecules. In the separation of hydrocarbon mixtures the elution of components is directed by the effective molecular volume exclusiveJy6. The following factors are mentioned in literature as having a bearing on the effective volume of molecules and which are in correlation with the elution volumes of hydrocarbons: the length of the hydrocarbon chain 7 • 8 , molar volume 9 • 1 0 , molecular mass 11 and various dimensions of molecular models 12 . Schulz 13 found in isoalkanes a relationship between the molar volume and the average number of synclinal (gauche) butane interactions in the molecule, which enables the computation of the elution data from the structure and the conformation. The majority of the relationships mentioned was inferred from the elution volumes of alkanes and aromatic hydrocarbons. No detailed data are available on gel chromatography of saturated polycyclic hydrocarbons.
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