取代基效应对二芳基硝酮CH=N(O)桥基1HNMR化学位移的影响  

Substituent Effects on the ~1H NMR Chemical Shifts of CH=N(O) Bridge Group in Diaryl Nitrone

作　　者：曹朝暾[1] 罗青青[1] 曹晨忠[1] CAO Chao-tun;LUO Qing-qing;CAO Chen-zhong(Key Laboratory of Theoretical Organic Chemistry and Function Molecule, Ministry of Education, Key Laboratory of QSAR/QSPR of Hunan Provincial Universities, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China)

机构地区：[1]湖南科技大学化学化工学院,理论有机化学与功能分子教育部重点实验室,分子构效关系湖南省普通高等学校重点实验室,湖南湘潭411201

出　　处：《波谱学杂志》2017年第1期69-77,共9页Chinese Journal of Magnetic Resonance

基　　金：国家自然科学基金资助项目(21272063);湖南省教育厅科研资助项目(14C0466);湖南省自然科学基金资助项目(14JJ3112)

摘　　要：合成一系列取代二芳基硝酮XArCH=N(O)ArY化合物测定其核磁共振氢谱(~1H NMR)指认出桥基CH=N(O)上质子的化学位移δ_(H[CH=N(O)]),定量研究取代基效应对δ_(H[CH=N(O)])的影响.得到一个4参数定量方程,标准偏差(S)为0.020,较好地表达了δ_(H[CH=N(O)])的变化规律.结果表明,该类化合物的δ_(H[CH=N(O)])主要受4个因素影响:X基团的场/诱导效应[σ_F(X)];Y基团的共轭效应[σ_R(Y)];基团X和Y之间的特殊交叉作用(△σ~2);以及基团X和O^-之间的特殊交叉作用[△σ~2_(X-O)].其中,△σ~2_(X-O)对δ_(H[CH=N(O)]变化的贡献超过70%.通过δH[CH=N(O)]与二芳基希夫碱XArCH=NArY桥基CH=N上质子化学位移的δ_(H(CH=N))比较发现,这两类化合物桥基上质子的化学位移之间没有良好的线性关系.因而,在应用NMR谱图解析有机化合物分子结构时,不能简单地用δ_(H(CH=N))的变化去类比δ_(H[CH=N(O)]的变化.A series of substituted diaryl nitrones XArCH=N(O)ArY were synthesized, and their 1H NMR spectra were measured. The 1H chemical shift of the CH=N(O) bridge groups, ? H[CH=N(O)], in each compound was determined. The effects of substituents X and Y on ? H[CH=N(O)] were investigated quantitatively. A four parameters correlation equation was constructed to model the changes of ? H[CH=N(O)] with substituents, yielding a standard error of 0.020. The result indicated that ? H[CH=N(O)] in substituted diaryl nitrones are mainly affected by four factors: field/inductive effect (S) of substituent X [σF(X)], conjugative effect of substituent Y [σR(Y)], substituent specific cross-interaction effect between X and Y (Δσ2 ) and substituent specific crossinteraction effect between X and O– [ _2(X-O )Δσ ]?? Among these factors, the contribution of _2(X-O )Δσ to ? H[CH=N(O)] was more than 70%. A comparison of ? H[CH=N(O)] in substituted diaryl nitrones to ? H(CH=N) of the CH=N bridge group in diaryl Schiff base XArCH=NArY revealed no good linear relationship between ? H[CH=N(O)] and ? H(CH=N). Therefore it should be noted that one cannot simply use the change of ? H(CH=N) to deduce the change of ? H[CH=N(O)] when carrying out organic molecule structure elucidation with NMR spectra.

关 键 词：核磁共振(NMR) 1HNMR化学位移 取代基效应 二芳基硝酮 二芳基希夫碱 基团特殊交叉作用 

分 类 号：O482.53[理学—固体物理]