Experimental and theoretical determinations of bond lengths in naphthalene, anthracene and other hydrocarbons

Abstract

Recent independent determinations by X-ray crystallography of the C—C bond lengths in naphthalene and anthracene are shown to agree well. The experimental values agree to about 0-01 Å with both the simple molecular orbital and simple Pauling theories. These theories also make satisfactory predictions for 1.2 : 8.9-dibenzacridine and chrysene (except for the bond most affected by steric hindrance). The agreement between the two theories for aromatic molecules is traced to a correlation of their respective bond orders. For ethylene, butadiene, cyclo octatetraene and diphenyl the Pauling method is superior to the simple m. o. method.