STRUCTURAL FEATURES OF COAL-TAR MALTENES BY FT-IR SPECTROSCOPY

Four bituminous coal tar maltenes were fractionated into saturates, aromatics, and polars by extrography and complexation chromatography on a silica gel/silver nitrate column. For each fraction, the integral absorptivities for aliphatic and aromatic hydrogen were determined by using FT-IR and H-1 NMR spectroscopy. Whereas the aromatic integral absorptivities have been found relatively independent on the polarity of the fractions, the values of the aliphatic integral absorptivities decreased from saturates to polars. This is most likely due to the structural inconsistency of the fractions and, simultaneously, the changes in dipole moments of the C-H bonds in alpha-position to the aromatic ring. The integral absorptivities previously published by Solomon were less suitable for calculation of aromaticity of polar fractions; however, an excellent agreement with H-1 NMR results has been found for maltenes and aromatic fractions.