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The secular equations corresponding to the five canonical structures for benzene and the forty-two for naphthalene, considered as six and ten-electron systems, respectively, are set up and solved with certain simplifying assumptions, leading to energy values differing by 1.1055α and 2.0153α, respectively, from those corresponding to unexcited (Kekulé-type) structures, α being a single exchange integral involving neighboring carbon atoms. Equating these values to the empirical values of the resonance energy, α is found to be about — 1.5 v.e. It is pointed out that the dissociation of certain substituted ethanes into free radicals is due not to weakness of the carbon-carbon bond in the ethane but to the stabilization of the free radicals resulting from resonance among the structures in which the unpaired electron is located on the methyl carbon and those in which it is on other atoms (ortho, para, etc., to the methyl carbon). The secular equations for a number of such radicals have been solved, neglecting excited structures. The experimentally determined heat of formation of hexaphenylethane from triphenylmethyl, 0.5 v.e., when equated to the calculated value C–C+2.2156α, with C–C = 3.65 v.e., leads to α = — 1.4 v.e. The calculated tendencies towards dissociation are in satisfactory agreement with observation, such features as the smaller dissociating power of β-naphthyl than of α-naphthyl and of biphenylene than of diphenyl being accounted for, so that resonance among the structures considered may be accepted as the principal effect causing the stability of the hydrocarbon free radicals.

Quinazolones are high-melting solids, stable to heat and resistant to degradative attack.' It was therefore of interest to prepare polymeric quinaeolones and to study some of their properties. Two polymers were synthesized by use of the reaction sequence shown in Figure 1. Pyromellitic dianhydride (PMDA) was treated with excess aqueous ammonia and heated to dryness. The pyromellitic diimide (PMDI) which formed during the prolonged heating was then subjected to Hofmann degradation. According to the literature* only p-diaminoterephthalic acid (DATA) is formed in this reaction. However, in the subsequent treatment of the DATA with acetic anhydride, two benzdi(methy1oxazones) (BDMO) were isolated. It is probable, therefore, that the Hofmann degradation gave a mixture of 4,6-diaminoisophthalic acid (DAIA) and DATA (approximately 80:20 ratio). (One possible explanation for this deviation from the data of the literature is that the PMDI contained some pyromellitic ammonium salts and amides.) Each of the BDMO compounds was reacted with 4,4'-oxydianiline (ODA) to give stereoisomeric polypyrimidone quinaeolones (PPQ) containing diphenyl ether linkages :After a solid-state molecular-weight build-up similar to a technique used for poly-benzimidaeoles3 the PPQ resins were infusible but dissolved readily in cresylic acid. In this solvent, the intrinsic viscosities of PPQ-I and PPQ-I1 were 0.46 and 0.62, respectively. At 300"C., in air, films of the two resins lost approximately 50% weight in 100 hrs.

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