A method for the calculation of molecular weights of aromatic compounds, and its application to petroleum fractions

Moderately accurate molecular weights of aromatic compounds containing only one basic aromatic system can be calculated using the ratio of peripheral carbon atoms (Cp) to the total number of aromatic carbon atoms (Ca). This ratio is readily determined from nuclear magnetic resonance/infra-red measurements and carbon-hydrogen analysis. Hydrogens in CH3 and CH2 groups in α-position to the aromatic ring were considered only in the n.m.r./ i.r. measurements of Cp and Ca when these calculations were applied to petroleum fractions. The method described here is applicable to compounds containing heteroatoms, and may also be used for average weights of mixtures. Sample contamination with non-aromatic hydrocarbons does not influence the calculated molecular weight.