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Electron Paramagnetic Resonance and Mass Spectroscopy Study of Spin-Trapped Radicals: Styrene-Amine Photoreactions

Volume 51, Number 6 (June 1997) Page 874-879

Lin, Chiou-Rong; Pan, Kai; Ho, Tong-Ing

The free radical intermediates from the photolysis of eleven substituted styrenes (1-11) with both tertiary and secondary amines were studied by spin trapping and the high-pressure liquid chromatography electron paramagnetic resonance (HPLC-EPR) technique. Eleven alpha -methylbenzyl radicals were trapped by 2-methyl-2-nitrosopropane (MNP) and separated by HPLC. Resolution enhancement was applied to obtain long-range hyperfine splitting constants (hfsc). The nitrogen hfsc are linearly correlated with the Hammett substituent constants. The major mass spectral fragments for the trapped aminoxyl radicals (12-22) include [M + 1]+, [M - 1]+, [MtBu]+ , [M-tBuOH]+, [M-tBuNO]+, and [(CH3) C3]+. The structures of 12-22 were also confirmed by chemical synthesis by adding Grignard reagent to alpha -phenyl- N - tert -butylnitrone (PBN) and its derivatives.