Interrelation of Dissociation Energy, Internuclear Distance and Bond Order for Carbon-Carbon Linkages

Abstract

Fox and Martin¹ have found that the heat of dissociation (D kgm.-cal.) for different carbon-carbon linkages (organic compounds, graphite, diamond) follows smooth curves when plotted against either internuclear distance (r_e angstroms) or bond order x. When the assigned values of any pair of the three magnitudes D, r_e, x are plotted against each other logarithmically, approximately linear relations are obtained, from the slopes and intercepts on the axes of which it may be deduced that the following relations should hold very approximately: Fox and Martin² have independently deduced the relation Dr³_e equals a constant, by a semi-empirical method, as consistent with a potential energy function of a simple form recently proposed by Sutherland, and with a modified Morse-Clark relation connecting bond constant k_e with r_e. It is of interest to note that the latter type of relation, originally devised for spectroscopic diatoms only, is found to have application to molecular linkages. This has also been shown by Thompson and Linnett³.