Research On The Mechanism Of Free Radical Reactions By CIDNP Technique

Single Electron Transfer (SET) reaction is a rising front field. Chemical Induced Dynamic Nuclear Polarization (CIDNP) technique is the useful means of studying the mechanisms of free radical reactions and the structures of reaction intermediates.It is important for the CIDNP experiment to control the light route. Thus, the excited light resource focusing control was made on the base of the previous light route of the lab, making light focusing well and making control flexible. So that requirement of the excited light intensity was satisfied.In this paper, the mechanisms of photo-reaction systems such as benzoquinone/benzodioxoles, 1-acetylisatin H-abstraction reduction and benzoquinone/ schiff bases were studied.1. Investigation on the photo-induced reaction mechanism of benzoquinone/benzodioxolesbenzoquinone/benzodioxoles was studied in the unpolar solvent C6D6 and polar solvent CD3CN by CIDNP technique, which indicates thatSolvent separated ion radical pairs (SSIP) are formed in acetontrile and neural radical pairs (RP) are formed in benzene as evidenced by the emissive and enhanced absorptive polarizations of methylene protons in CD3CN and C6D6, respectively. Therefore, the polarity of the solvent has significant effect on the reaction path.2. Investigation on the photo-reduction of 1 -acetylisatin H-abstraction The reactions of benzalhyde, 1-acetylisatin/benzalhyde and1 -acetylisatin/penol were studied by CIDNP technique. The results show that the excited state of 1-acetylisatin acquires the hydrogen proton of phenol hydroxy by carbonyl oxygen, producing free radical pairs. During the photo-reaction of 1-acetylistin with piperonals, the carbonyl oxygen acquires the methylene proton of piperonals and form free radical pairs, producing nuclear polarizations. And the free radical reaction mechanism of photo-induced H-abstraction was come up with.3. Investigation on the photo-induced reaction mechanism of benzoquinone/schiff basesThe photo-CIDNP studies on the benzoquinone/schiff bases indicate that the methine protons of schiff bases produce emission polarization in polar solvent CD3CN, which was caused by electron transfer reaction, while nuclear polarization was not observed in the unpolar solvent...