摘要:
2-Methyl-2-nitrosopropane (MNP) was used as a spin-trap reagent to study the radicals formed in the photochemical reaction of substituted trans-stilbenes (TS) with tertiary amines. Seven 1,2-(p,p'-disubstitited phenyl)ethyl radicals were trapped by MNP and isolated and identified by HPLC-EPR. The nitrogen hyperfine splitting constants (hfsc) of these radicals are linearly correlated with the Hammett substituent constants sigma-P. There is also a linear correlation of the nitrogen hfsc with both the single sigma-P parameter and the dual sigma-R', sigma-I parameters. The inductive and resonance effects are of equal importance. The correlation between proton hfsc and a single sigma-P parameter is not linear. There is fair correlation between the beta-proton hfsc and the dual parameters sigma-R', sigma-I. The only fair correlation may be due to the large dihedral angle between the nitrogen pi orbital and the N-C-H plane.