Differential gas–liquid chromatographic behaviour in diastereoisomeric systems. Part II. Assignment of diastereomer configuration in 2,3-dipentylbutanes and 2,4-dipentylpentanes

Abstract

During the preparation of the ditoluene-p-sulphonates of 2,3-dipentylbutane-1,4-diols and 2,4-dipentylpentane-1,5-diols, two competing reactions occurred; the ditoluene-p-sulphonylation and the formation of the appropriate cyclic ethers. Each of the meso-isomers produce a mixture of meso-ditoluene-p-sulphonyl derivative and the cis-cyclic ethers while the (±)-isomers from a mixture of the (±)-ditoluene-p-sulphonyl derivatives and the trans-cyclic ethers. As a result of a difference in the activation energy of formation, the cis- and trans-isomers of each cyclic compound are obtained in unequal amounts with the trans in majority; thus the corresponding ditoluene-p-sulphonyl products are obtained proportionally unbalanced with the (±)-form in minority. The ditoluene-p-sulphonyl derivatives are quantitatively reduced to the corresponding hydrocarbons and after chromatography, help to determine the relative retention times and volatilities of the meso-(±) and cis–trans pairs in the 3,4-dipentyltetrahydrofurans, 3,5-dipentyltetrahydropyrans, 2,3-dipentylbutanes, and 2,4-dipentylpentanes.