Study on the Chemical Structure of the Asphalt-like Substance Excavated from Jomon Ruins

Abstract

A structural investigation has been made of an asphalt-like substance of the Jomon era excavated from the Korekawa ruins in Aomori by means of proton magnetic resonance spectroscopy, measurement of mean molecular weight, elementary analysis and infrared spectroscopy.
NMR and IR spectra of the substance are very similar to those of heavy fractions of petroleum. The specimen has a relatively high hydrogen content (9.3%) and a relatively low oxygen content (4.7%). These data shows that it has the characteristics of heavy fractions of petroleum rather than those of coal.
The fundamental structure of the substance consists of the condensed aromatic ring sheets and its condensation form is of an intermediate one of peni- and kata-type. More than 30% of the peripheral protons on the aromatic rings are substituted with paraffinic chains having about 7 carbon atoms. The substance is thus low in aromaticity.
The substance is presumed to have been in contact with oxygen and moisture in air for a long period of time in the course of which the light fractions volatilized and the remaining heavy fractions were subjected to concentration as well as a series of reactions such as oxida- tion, dehydrogenation, condensation and polymerization. Consequently, the precursor of the substance studied should have been lower in oxygen content, in condensation degree of aro- matic rings and in aromaticity than the substance itself. These speculations further suggest that the substance studied was not derived from coal source but from petroleum source.