Thermal Stability of Polynuclear Aromatic Hydrocarbons and the Polarographic Half-wave Reduction Potential

Abstract

WE have noted a relation of the thermal stability of certain polynuclear aromatic hydrocarbons to the polarographic half-wave potential. In attempting to find some theoretical justification for this relation, it was found that Bergman¹ had related the E_1/2 to the ‘p’ ultra-violet band as determined by Clar². Also, Basu³ has related the E_1/2 to the lowest unoccupied energy orbital. Thermal stabilities were determined by Madison⁴ by pyrolysis followed by mass spectrometric analysis of the gas phase products. Table 1 presents the composite data: there the compounds are grouped into classes on the basis of Bergman's classification. The groups have theoretical justification in so far as that compounds of the same class plot linearly with respect to E_1/2 versus ‘p’ band frequency. Further, comparisons are valid: (a) if the compounds are planar molecules of the same class; and/or (b) if the compounds are members of an anellation series (for example, naphthalene, anthracene, naphthacene).