Structural Analysis of Pyridine Extract of Akabira Coal by 13C-and 1H-NMR Spectra

Abstract

Petroleum ether soluble part of pyridine extract of Akabira coal was fractionated by column chromatography of alumina into five fractions (Fr.A to E), and each fraction was analyzed by 13C-and 1H-NMR spectra. Furthermore, the average mol-ecular structure parameters for the Fr. B to E were calculated from the results of 1H-NMR and quantitative 13C-NMR spectra, elementary analysis and average molecular weight. The quantitative 13C-NMR spectra were measured by the combined use of the chrominum acetylacetonate relaxation reagent and the gated decoupling sequence.The absence of signal in the 24.4-29.4 and the 29.7-31.3 ppm ranges in the 13C-NMR spectrum of Fr. A is indicative of the absence of cyclic alkanes. Consequently, Fr. A con-sists of unbranched C22-37 alkanes and branched alkanes.From the structural parameters, it would be said that the constitutions of Fr. B to E consist of 2 to 4 aromatic rings and 0 to 2 naphthene rings, and percent substitution of alkyl groups on nonbridge aromatic ring carbons are 30-40%.