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Stereochemistry of nitrate esters of polyols Livingstone, David James

Abstract

The solution infrared spectra and proton magnetic resonance (PMR) spectra of several series of polyol nitrates have been examined in order to assess the potential of these two spectroscopic methods for the study of the stereochemistry of nitrate esters in solution. This thesis reports the first systematic study of the solution infrared spectra of nitrate esters. Correlations of the frequencies of the three principal nitrato group bands with structure and stereochemistry were observed for 1, 4:3, 6-dianhydrohexitol, benzocycloalkane, cyclohexane, sugar, 1, 2-diphenylethane, and polyhydric alcohol nitrates. The frequencies of the Ʋa(NO₂) and Ʋ (ON) bands were clearly dependent on molecular structure while that of the Ʋs(NO₂) band exhibited a marked steric dependence. On the basis of their solution infrared spectra, configurations were assigned to several 1,4:3,6-dianhydrohexitol mononitrates which were consistent with other properties of these compounds. A rationale of certain aspects of the spectral correlations is presented. Examination of the PMR spectra of the nitrate esters and of other esters of polyhydric alcohols revealed a relationship between molecular symmetry and the multiplicity of methylene resonances. The PMR spectrum of glycerol trinitrate could be classified as that of an (AB)₂X system and a complete spectral assignment was possible for both the methine and methylene resonances. The effect of solvent and substituent on the methylene chemical shifts of pentaerythritol derivatives has been studied on a qualitative basis and the application of PMR spectroscopy to the elucidation of the structure of previously unreported 1,2-O-isopropylidene- α-D- glucofuranose- 3, 5, 6-trinitrate, for which a complete PMR spectral assignment was possible, is described. Thin-layer chromatography (TLC) has been successfully applied to the polyol nitrates and for several groups of these a dependence of Rf value upon stereochemistry has been noted. A stereoselective detection has been found for the 1, 4:3, 6-dianhydrohexitol nitrates and a preliminary study (by TLC) of the reactions of a homologous series of twelve polyhydric alcohol nitrates with pyridine indicated large differences between the rates of reaction of homologues but not of diastereoisomers. The p-toluenesulfonate and p- bromobenzenesulfonate esters of 1, 4:3, 6-dianhydro-D- glucitol- 5-nitrate, 1, 2- O-isopropylidene-α-D- glucofuranose-3, 5, 6-trinitrate, pentaerythritol trinitrate p-bromobenzene sulfonate, allitol hexabenzoate, L-threitol tetrani-trate, L-iditol hexanitrate, and D-talitol hexanitrate are reported for the first time.

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