August 1972

Document Type


Degree Name



Dept. of Chemistry


Oregon Graduate Center


Orbital symmetry considerations suggest that cheletropic fragmentation of 2,5-diphenyl-3,4-diazacyclopentadienone-3,4-dioxide (5[underline ≈]) along the thermally allowed [ δ[superscript 2] s + δ [superscript 2] s + δ [superscript 2] a + ω [superscript 2] s] pathway would yield benzonitrile oxide and carbon monoxide as primary products. However, experiments show that benzonitrile and carbon dioxide are the major products in solid phase and dilute solution pyrolyses of 5[underline ~] in complete agreement with its mass spectral fragmentation. Benzonitrile oxide and carbon monoxide are produced, but the major reaction pathway is not the postulated cheletropic fragmentation. The rate of disappearance of 5[underline ~] during dilute solution pyrolysis is first order in [5[underline ~]]; k = 2.08 x 10[superscript -4] sec [superscript -1] (157-58°), ΔG[superscript +] = 32.7 kcal/mole. A scheme is proposed which accounts for the formation of the major products in the thermal and mass spectral fragmentation of 5[underline ~], and the mass spectrum of 2, 5-dicarbomethoxy-3,4-diazacyclopentadienone-3,4-dioxide is discussed. Total pi bond orders calculated by the simple HMO method are discussed as a means of predicting mass spectral fragmentation and correlation of mass spectral and thermal processes for the compounds examined. An unsuccessful attempt to synthesize 3,4-diazacyclopentadienorie- 3,4-dioxide is described.





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