CHARACTERIZATION OF SMITHS NITRENE AND 1-PHENYL-3-(ALPHA-CYANO)BENZYLIDENETRIAZENE WITH THEORETICAL, NMR, AND FLASH PHOTOLYTIC METHODS

Doubly enriched (C-13, N-15) 1-phenyl-3-(alpha-cyano)benzylidenetriaze ne, Ph-N=N-N=C(C*equivalent to N)-Ph, did not show C-13-N-15 splittin gs in the NMR spectra in solution that would be expected from the pres ence of a cyclic nitrene in reversible equilibrium, a theory proposed in 1964 by Smith, Krbechek, and Resemann to explain its chemical behav ior. Molecular orbital calculations at the 6-31G level on the core st ructures (Ph replaced by H) also indicated substantially greater stabi lity for the open-chain compound. Flash photolysis (337 nm) of 1,4-dip henyl-5-azido- 1,2,3-triazole in solution led to the open-chain triaze ne within about 20 ns but with no observable transient absorbing speci es.