氮氧自由基中的多光子化学反应(Ⅰ)(英文)

MULTI-PHOTON CHEMICAL REACTION IN NITROXIDE FREE RADICALS (Ⅰ)

在不同光源照射下，作者利用乙基亚硝基有机化合物在乙醇溶剂下，产生双光子的化学反应，用电子自旋共振吸收谐振腔为反应器．在不同的流速下，生成3种同分异构自由基．其结构由电子自旋共振光谱确定、微观的氢键跳动频率由不同波形的氮核超精细偶合常数的变化而确定、利用Charm软件计算，确定β-氢超精细偶合常数的意义及其几何形状．

In order to understand the simultaneous interactions of nitric oxide and reactiveintermediates derived from ethanol in the blood stream and liver within our human body, wechose ethyl nitrite, a compound synthesized from ethanol and sodium nitrite at neutral pHvalue, equivalent to physiological conditions, to study the radical intermediates during pho-tolysis within the ESR,cavity with various light power sources. Under a two-photon Chemicalreaction pathway, three isomer radicals were formed and characterized by their ESR spec-tra. The intermolecular formation of these isomeric radicals and the unequivocal detectionof two diastiomeric, two strongly intramolecular hydrogen bonded di-α-hydroxyethyl nitrox-ide radicals are of considerable interests by the investigation of dynamic alternate linewidthvariations of the nitrogen isotropic hyperfine splittings. Different kinetic flow experimental studies indicated one photon process for the for-mation of ethoxyl-ethyl nitroxides. Under a more intense light source, from the orbitalinteractions and correlation diagrams, the homolytic α-cleavage reaction similar to the n,π states of ketones (so-called 'Norrish Type I' reaction) is initiated by the absorption ofa photon to promote another n-orbital electron mainly on the oxygen atom of alkoxy groupinto the electrophilic half-filled π-orbital. Two-photon process will generate two (d,l andmeso form) di-α-hydroxyethyl nitroxides.The potential surfaces of the rotations of two methyl groups in both isomers were stud-ied by the charm software. Due to van der waals interactions, the two methyl groups arehighly hindered rotated with approximately 150 kJ/mol in planar structure of the meso formof di-α-hydroxyethyl nitroxide, where the two methyl groups in the d,l form is about 3.3kJ/mol. The assignment of the β- proton hyperfine splitting constants of the two isomersare based on molecular models and McConnell's equation. Their production rates are asym-metrical in solution with 60 % for meso-form and 40 % for d,1-form. Based on the alternatelinewidth effects of the nitrogen hyperfine splittings, the jump rates of the two hydroxylprotons in the planar di-a-hydroxyethyl nitrokides are estimated t0 be about l0-ll s.