基团共轭效应的经验标度

本文以一取代苯为基本模型,假设取代基对苯环间位和对位上质子的诱导效应大致相等,且间位上的共轭效应受阻,则对位上质子的化学位移(δ_p)与间位上质子的化学位移(δ_m)之差与取代基的共轭效应成正比。因此,共轭效应强度R_H可由下式求得:R_H=1.6(δ_p-δ_m)利用此式,作者计算了一些常见的基团的共轭效应强度,其结果与文献报道值颇为一致,且表现出明显的变化规律。     

从13C化学位移分析取代基的诱导效应、共轭效应和亲电取代反应活性间的关系

以单取代苯为模型,建立并论证了取代基诱导效应参数RI、共轭效应参数RC及诱导和共轭共同作用效应参数R,RI=128.5-δ1,RC=642.5-∑6n=2δn,R=771-∑6n=1δn,δn(n=1～6)是单取代苯苯环上6个碳原子Cn(n=1～6)的化学位移,δ1是取代位C1的化学位移,128.5为苯的13C化学位移。当参数R>0时,取代基对苯环有给电子效应。一般而言,RI<0、RC>0、R>0时,取代基是典型的使苯环活化的邻对位定位基;RI<0、RC<0、R<0时,取代基是使苯环钝化的间位定位基;其余情况参考δn的具体数值判定取代基的作用。能与苯环形成最佳共轭的基团,其与苯环直接相连的是与碳原子同周期的B、C、N、O、F。     

取代苯乙酮羰基17O-NMR化学位移的规律

提出计算取代苯乙酮羰基17O-NMR化学位移的公式δcal=550.0+△o+△m+△p,通过线性回归法确定了12种取代基参数.以44种取代苯乙酮为样本点作回归检验表明该公式的置信度为99.5%,计算值与实验值的偏差△δ在5.0(相对误差约0.5%)以内的羰基17O-NMR化学位移的计算值在90%左右.     

三苄基锡羧酸酯的合成及其结构表征

本文以(三苄基锡)氧化物和相应的羧酸反应, 合成了20个三苄基锡羧酸酯, 由波谱对结构的研究表明, 红外光谱的酰基振动频率与羧基上取代基的空间和电子效应密切相关, 三苄基锡羧酸酯的结构微小变化, 明显地反映了^1^1^9Sn和^1^3CNMR化学位移的差异, ^1^1^9Sn化学位移与三苄基锡取代的苯甲酸酯的对位取代基Hammett常数(σ)之间存在着良好的线性关系: δ~1~1~9~S~n=15.48σ+14.23, n=7, r=0.995, 去烃基化是这一类化合物质谱裂解的特点。     

基团的电子效应与单取代苯对位^1H,^13C的化学位移

基团的电子效应与单取代苯对位１Ｈ、１３Ｃ的化学位移＊韩长日冯娇杨钟照平（海南师范学院化学系海口５７１１５８）关键词１Ｈ的化学位移１３Ｃ的化学位移基团电负性共轭效应引言在１Ｈ、１３Ｃ核磁共振谱中，化学位移值的大小主要取决于屏蔽作用的大小，而屏蔽作用的大...     

唑烷环-Schiff碱互变异构中取代基效应和溶剂效应的NMR研究

合成了十个对位和间位取代的2-苯基-4,4-二基 唑烷, 并用NMR研究了它们在氯仿、丙酮和二甲基亚砜中与相应的Schiff碱之间的互变异构平衡。发现在平衡常数K与取代基常数σ^+之间存在着良好的线性自由能关系, 说明平衡可能经历了带有正电荷的中间体。在2-位质子的化学位移δ与取代基常数σ间也存在着线性关系。logK/K0-σ^+和δ-σ直线的斜率都与溶剂的极性有关。     

唑烷环-Schiff碱互变异构中取代基效应和溶剂效应的NMR研究

合成了十个对位和间位取代的2-苯基-4,4-二基 唑烷, 并用NMR研究了它们在氯仿、丙酮和二甲基亚砜中与相应的Schiff碱之间的互变异构平衡。发现在平衡常数K与取代基常数σ^+之间存在着良好的线性自由能关系, 说明平衡可能经历了带有正电荷的中间体。在2-位质子的化学位移δ与取代基常数σ间也存在着线性关系。logK/K0-σ^+和δ-σ直线的斜率都与溶剂的极性有关。     

三[(苯基二甲硅基)亚甲基]锡 O,O-二芳基二硫代磷酸酯的研究

本文合成了十五个新的[苯基二甲硅基]锡O,O-二芳基二硫代磷酸酯。测定了它们的IR, ^1H, ^1^3C, ^1^1^9Sn NMR及MS, ^1^1^9Sn NMR的化学位移δ和芳环对位取代基的Hammett常数σ之间存在良好的线性关系。     

离子性指数、极化效应指数烷烃^13C NMR化学位移的 关系研究

定义了烷烃分子中碳原子的离子性指数(INI)，用离子性指数(INI)、极化效应指数(PEI)及N^i~H(i=αβΥ)结构信息参数研究了烷烃的^13CNMR化学位移模型，结果表明，烷烃^13CNMR化学位移(CS)可用下式来定量描述：CS=194.6156-37.7394(INI)+98.6505(ΣPEI)+27.1630(INI/ΣPEI)-652.9106(ΣPEI/INI)+0.7735N^α~H+2.2468N^β~H-0.1742N^γ~H。用上式估算了304个碳原子的化学位移，平均绝对误差仅为0.77δ，标准差0.9860δ，预测值与实验值非常吻合。     

金属羰基化合物的氧原子转移反应——取代亚碘酰苯存在下Cr(CO)6的CO取代反应动力学研究

在取代亚碘酰苯存在下,研究了Cr(CO)₆与外来配体L(L=CH₃CN、PPh₃)间的羰基取代反应动力学.结果表明,该试剂的空间效应加快了反应速度,其活性顺序为:邻位取代>间位取代>对位取代>未取代;不同基团的对位取代亚碘酰苯的电子效应与氧原子转移速度之间呈良好的线性关系.吸电子基促进反应,在位阻相近的情况下,取代亚碘酰苯的活性随I-O键强减小而增大.     

Prediction of the 13C NMR Chemical Shifts of Fluorenone Analogues by the GIAO Method

After the geometry optimization at B3LYP/6-31+G(d,p) level,the NMR calcula-tions of a series of fluorenone analogues have been carried out by GIAO method at HF/6-31+G(d) level and B3LYP/6-311G+(2d,p) level,respectively.The 13C NMR chemical shifts calculated at HF/6-31+G(d) level show better agreement with the observed values.By a series of linear correction equations (δpred=a + bδcalc),accurate prediction of 13C chemical shifts was achieved for the new fluorenone compound.The linear correlation of δpred with δexptl is excellent,and the square of correlation coefficient,r2,is up to 0.994.The maximum absolute difference between δpred and δexptl,Δδ,is 4.6 ppm,and the root-mean-square error between δpred and δexptl is only 2.6 ppm.     

^1^3C化学位移在达玛烷型皂甙结构研究中的应用

本文将迄今为止国内外文献报道的200余种达玛烷型皂甙类化合物的^1^3C化学位移按其结构特征分类整理，以原人参二(三)醇等为模型化合物，讨论了皂甙元结构变化引起的位移变化(△δC)规律。     

Prediction of the ~(13)C NMR Chemical Shifts of 9,10-Dihydrophenanthrene Analogues by the GIAO Method

After the geometry optimizations at the B3LYP/6-31+G(d,p) level, the NMR calculations of a series of 9,10-dihydrophenanthrene analogues have been carried out by GIAO method at the HF/6-31+G(d) level. The calculated 13C NMR chemical shifts are in agreement with the observed values. By a series of linear correlation equations (δpred = a + bδcal.c) of the 13C chemical shifts, accurate prediction of 13C chemical shifts was achieved for the new 9,10- dihydrophenanthrene compound, for which the predicted 13C NMR chemical shifts are in quite good agreement with the experimental values. The linear correlation between δpred and δexptl is excellent, and the square of correlation coefficient, r2, is up to 0.9973. The maximum absolute difference between δpred and δexptl, Δδ, is 4.5 ppm, and the rms error between δpred and δexptl is 2.55 ppm. In the meantime, according to the theoretical predicted result, we could confirm that the new 9,10-dihydrophenanthrene analogue is erianthridin (2,7-dihydroxy-3,4-dimethoxy-9,10-dihydro-phenanthrene).     

1H, 13C, 195Pt and 15N NMR structural correlations in Pd(II) and Pt(II) chloride complexes with various alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline

(1)H, (13)C, (195)Pt and (15)N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with such alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline as LL = 6,6'-dimethyl-bpy, 5,5'-dimethyl-bpy, 4,4'-di-tert-butyl-bpy, 2,9-dimethyl-phen, 2,9-dimethyl-4,7-diphenyl-phen, 3,4,7,8-tetramethyl-phen, having the general [M(LL)Cl(2)] formula were performed and the respective chemical shifts (δ(1H), δ(13C), δ(195Pt), δ(15N)) reported. (1)H high-frequency coordination shifts (Δ(coord)(1H) = δ(complex)(1H)-δ(ligand)(1H)) mostly pronounced for nitrogen-adjacent protons and methyl groups in the nearest adjacency of nitrogen, as well as (15)N low-frequency coordination shifts (Δ(coord)(15H) = δ(complex)(15H)-δ(ligand)(15H)) were discussed in relation to the molecular structures.     

How reliable are GIAO calculations of 1H and 13C NMR chemical shifts? A statistical analysis and empirical corrections at DFT (PBE/3z) level

Reliability of calculated (1)H and (13)C NMR chemical shifts for various classes of organic compounds obtained with gauge-invariant atomic orbital (GIAO) approach has been studied at the PBE/3ζ level (as implemented in PRIRODA code) using linear regression analysis with experimental data. Empirical corrections for the calculated chemical shifts δ(H,calc) = δ(PBE/3ζ) - 0.08 ppm (RMS 0.18 ppm, MAD 0.66 ppm) and δ(C,calc) = δ(PBE/) (3) (ζ) - 6.35 ppm (RMS 3.09 ppm, MAD 9.42 ppm) have been developed using the sets of 263 and 308 experimental values for (1)H and (13)C chemical shifts, respectively. The confidence intervals of NMR chemical shifts at 95% confidence probability are δ(H,calc) ± 0.35 ppm for (1)H and δC,calc) ± 6.05 ppm for (13)C.     

Solid state NMR spectroscopy as a precise tool for assigning the tautomeric form and proton position in the intramolecular bridges of o-hydroxy Schiff bases

Two analogous Schiff bases, (S,E)-2-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylimino)methyl)phenol (1) and (S,Z)-2-hydroxy-6-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylamino)methylene)cyclohexa-2,4-dienone (2), exist in the solid state as phenol-imine and keto-amine tautomers, respectively. Their crystal structures were solved using the X-ray diffraction method. Sample 1 forms orthorhombic crystals of space group P2(1)2(1)2(1), while 2 forms monoclinic crystals of space group P2(1). In each sample, one molecule is in the asymmetric unit of the crystal structure. One-dimensional and two-dimensional solid state NMR techniques were used for structure assignment and for inspection of the (13)C and (15)N δ(ii) of the chemical shift tensor (CST) values. NMR study indicates that the span (Ω = δ(11)-δ(33)) and the skew (κ = 3(δ(22)-δ(iso)/Ω) are extremely sensitive to change in the tautomeric form of the Schiff bases. Theoretical calculations of NMR shielding parameters for 1 and 2 and a model compound with reduced aliphatic residue were performed using the GIAO method with B3LYP functional and 6-311++g(d,p) basis sets. From comparative analysis of the experimental and theoretical parameters, it was concluded that the position of hydrogen in the intramolecular bridge has tremendous influence on (13)C and (15)N CST parameters. Inspection of Ω and κ parameters allowed for the establishment of the nature of the hydrogen bonding and the assignment of the equilibrium proton position in the intramolecular bridges in the solid state.     

固体化合物YbCl~2和AYbI~3(A=Cs,Rb, K)中^1^7^1Yb NMR谱 及核磁屏蔽性质

首次在室温下测定了^1^7^1Yb在YbCl~2中的化学位移、化学位移各向异性、自旋-晶格弛豫时间、自旋-晶格弛豫时间的各向异性,计算出自旋-自旋弛豫时间。根据TMS(^1H)的绝对屏蔽常数,计算了^1^7^1Yb在YbCl~2和在AYbI~3(A=K,Rb,Cs)中的平均绝对屏蔽常数(σ~i~s~o),逆磁绝对屏蔽常数(σ~i~s~o^d)和顺磁绝对屏蔽常数(-σ~i~s~o^p),并且对^1^7^1Yb的各项屏蔽常数与结构之间的关系进行了讨论。     

Carbon-13 NMR spectra of monosubstituted pyrazines

Carbon-13 NMR chemical shifts and one-bond carbon–hydrogen coupling constants have been obtained at 15·09 MHz. The trends in the carbon chemical shifts obtained for the pyrazines parallel those of monosubstituted benzenes and 2-substituted pyridines, except for the direct effect of substitution where the pyrazines resemble pyridines not benzenes. The substituent effects on the ¹³C NMR spectra are generally quite similar to those in the ¹H NMR spectra. The ¹³C NMR spectrum of the tautomeric hydroxypyrazine has been compared with the ¹³C NMR spectra of 2-, 3- and 4-hydroxypyridines. Hydroxy compounds that can exist as a cyclic amide show a large meta substituent effect on the chemical carbon shift.     

Comparison of the substituent effects on the 13C NMR with the 1H NMR chemical shifts of CHN in substituted benzylideneanilines

Fifty‐two samples of substituted benzylideneanilines XPhCH?NPhYs (XBAYs) were synthesized, and their NMR spectra were determined in this paper. Together with the NMR data of other 77 samples of XBAYs quoted from literatures, the ¹H NMR chemical shifts (δ_H(CH?N)) and ¹³C NMR chemical shifts (δ_C(CH?N)) of the CH?N bridging group were investigated for total of 129 samples of XBAYs. The result shows that the δ_H(CH?N) and δ_C(CH?N) have no distinctive linear relationship, which is contrary to the theoretical thought that declared the δ_H(CH?N) values would increase as the δ_C(CH?N) values increase. With the in‐depth analysis, we found that the effects of σ_F and σ_R of X/Y group on the δ_H(CH?N) and the δ_C(CH?N) are opposite; the effects of the substituent specific cross‐interaction effect between X and Y (Δσ²) on the δ_H(CH?N) and the δ_C(CH?N) are different; the contributions of parameters in the regression equations of the δ_H(CH?N) and the δ_C(CH?N) [Eqns 4 and 7), respectively] also have an obvious difference. Copyright © 2015 John Wiley & Sons, Ltd.