Gasphasenthermolyse von Pyrazolinen, 3 [1] . Elektronische Struktur und Gasphasenpyrolyse von 4‐substituierten 3,5,5‐Trialkyl‐3,5‐dihydro‐4 H ‐1,2,3‐triazolen untersucht durch Photoelektronenspektroskopie und semiempirische Rechnungen

Gas‐Phase Thermolysis of Pyrazolines, 3 [1] . – Electronic Structure and Gas‐Phase Pyrolysis of 4‐Substituted 3,5,5‐Trialkyl‐3,5‐dihydro‐4 H ‐1,2,3‐triazoles Studied by Photoelectron Spectroscopy and Semiempirical Calculations The PE spectra of the 3,5‐dihydro‐4 H ‐1,2,3‐triazoles 1–3 have been recorded. The ionization potentials have been assigned to molecular orbitals on the basis of MNDO, AM1, and PM3 calculations. The most important occupied MOs are characterized as π NNN , π C=X (X = O, NCH 3 , CH 2 ), n N‐3 , n NN + , n NN – and n X . The gas‐phase thermolyses of 1–3 have been studied by PE‐controlled real‐time gas analysis. After extrusion of molecular nitrogen, the remaining reactive species cyclize to three‐membered rings. At higher temperatures and in flash vacuum pyrolysis, subsequent reactions lead to smaller acyclic compounds.