【摘要】 对4-氧-2,2,6,6-四甲基哌啶-1-氧自由基在26种不同溶剂中的顺磁共振谱进行了测定,发现超精细分裂常数A_N随溶剂极性的增加而上升,而g值却呈现微小的下降趋势。A_N与Reichardt E_T、Kosower Z值之间有线性关系,而与ε、μ却不呈现线性关系。由于E_T、Z为模型反应的溶剂微观极性效应参数,而ε、μ为非模型反应的溶剂宏观极性效应参数,所以A_N可以作为一种新的非模型反应的溶剂微观极性效应参数。用HMO方法计算了氮氧自由基中异核双原子三电子键（N—O）的成键和反键轨道能量,采用Streitwieser所推荐的杂原子h_i和K_ij的半经验数值,结果表明离域能在0.4—0.5β范围,与丁二烯的离域能（NMO法）相当,定性地说明了氮氧自由基的稳定性以及溶剂极性对π电子密度分布的影响。更多还原

【Abstract】 The electron spin resonance spectra of 4-oxo-2,2,6,6-telramethy 1-piperidine-1-oxyl in twenty-six solvents of different polarity were deter mined.It was found that the hyperfinc splitting constant AN increased with the increase of the polarity of the solvent while the g value showed a tendency of slight decrease.There was a linear correlation of the AN value with Reichardt ET and Kosower Z,but no such correlation was found with e or μ Since ET,Z are microscopic solvent polarity parameters for model reactions whereas ε,μ macroscopic solvent polarity parameters for nonmodel reactions,AN can thus be used as a microscopic solvent polarity parameter for nonmodel reactions.The bonding molecular orbital energy and antibonding molecular orbital energy of the hcteronuclear diatomic three electron bond in nitroxide were calculated by HMO method,using the semi-empirical value of hi and kii parameters for heteroatoms given by Streitwieser,and it was shown that the delocalization energy was within the range of 0.4-0.5β,comparable to that for butadiene (HMO method).The results could account for the stability of nitroxide radical and also the solvent effect upon the distribution of π-electron density.The electron spin resonance spectra of 4-oxo-2,2,6,6-telramethy 1-piperidine-1-oxyl in twenty-six solvents of different polarity were deter mined.It was found that the hyperfinc splitting constant AN increased with the increase of the polarity of the solvent while the g value showed a tendency of slight decrease.There was a linear correlation of the AN value with Reichardt ET and Kosower Z,but no such correlation was found with e or μ Since ET,Z are microscopic solvent polarity parameters for model reactions whereas ε,μ macroscopic solvent polarity parameters for nonmodel reactions,AN can thus be used as a microscopic solvent polarity parameter for nonmodel reactions.The bonding molecular orbital energy and antibonding molecular orbital energy of the hcteronuclear diatomic three electron bond in nitroxide were calculated by HMO method,using the semi-empirical value of hi and kii parameters for heteroatoms given by Streitwieser,and it was shown that the delocalization energy was within the range of 0.4-0.5β,comparable to that for butadiene (HMO method).The results could account for the stability of nitroxide radical and also the solvent effect upon the distribution of π-electron density.更多还原