Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The PE spectra of the 4,5-dihydro-3H-pyrazoles 1, 2, of 2,5-dihydro-1,3,4-oxadiazole 3, and 2,5-dihydro-1,3,4-thiadiazole 4 have been recorded. Based on HAM/3, MNDO, AM1, and PM3 calculations, the ionization potentials have been assigned to molecular orbitals. The gas-phase thermolyses of 1-4 have been studied by PE-controlled gas analysis. Extrusion of molecular nitrogen leads to reactive species which cyclize to three-membered rings of different stability. At higher temperatures and in flash vacuum pyrolysis, consecutive reactions may lead to smaller acyclic molecules. The cyclo-propanol 7, obtained by denitrogenation of 2, is thermally rather stable. Its PE spectrum has been recorded and analyzed.
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