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1.
B环对位取代异黄酮化合物的核磁共振研究 总被引:5,自引:0,他引:5
对14个合成的B环对位取代异黄酮化合物核磁共振氢谱进行了研究.利用超导核磁共振归属了B环无取代异黄酮质子的化学位移,根据取代基化学位移的变化影响规律考察了取代基对分子的影响方式.研究结果表明,2'(6'),3'(5')位质子共振迁移分别与取代基参数σp和So线性相关,说明4'位取代基主要通过电子效应影响其间位质子,其磁各向异性仅影响邻位质子,该取代基对A环质子影响不大,而对C环尤其是对2-H影响较明显. 相似文献
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在B3LYP/6-31G**水平下优化了几种B环间位取代异黄酮衍生物的几何构型,在B3LYP/6-311G**水平下计算了该类化合物的核磁共振谱。研究结果表明:在1E!1H和2E~2H中的分子内氢键,其键长为0.1668nm,使整个分子形成一个四环的交叉共轭体系。从9位羟基取代对异黄酮衍生物NMR数据的影响来看,相邻的碳和相邻的氢化学位移的减少是由于电子云密度的增加和屏蔽作用的加强。而相邻碳的化学位移增加更大。此外,从取代基对化学位移的影响进行了讨论。邻对位氢的化学位移与取代基使苯环电子云密度增大的趋势相一致。A环和C环上的氢基本不受取代基的影响。对位碳的化学位移则与取代基使苯环电子云密度增大的趋势相反,邻位碳的化学位移变化趋势不明显。 相似文献
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取代基对苯环~(13)C和环上质子化学位移的影响具有加和性,基于这一性质而进行的化学位移计算已广泛应用于分子结构的测定.我们发现,取代基对苯环质子偶合常数的影响也具有近似的加和性,并提出简单的计算公式.偶合常数计算与化学位移计算结合起来,可更有效地用于分子结构测定. 苯环上质子间偶合常数的计算公式可表示如下: 相似文献
4.
采用自由基比色法考察苯并呋喃酮衍生物结构对其DPPH捕获能力的影响。结果发现,母体苯环5,7位上甲基和叔丁基的改变以及取代苯环上强供电子取代基的存在对苯并呋喃酮衍生物的DPPH捕获能力没有明显影响。取代苯环2’位存在明显的位阻作用,对苯并呋喃酮衍生物的DPPH捕获能力具有明显的抑制作用:并且当此位为不含活泼氢的氢键受体取代基时,苯并呋喃酮衍生物的DPPH捕获能力会由于取代基与3位活泼氢的氢键作用而被进一步削弱;但此位为含有活泼氢的氢键受体取代基时,此取代基的氢将会由于3位活泼氢与取代基的氢键作用而活化,从而使其位阻作用得到一定程度的抑制。 相似文献
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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 总被引:3,自引:0,他引:3
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。 相似文献
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采用核磁共振氢谱对合成的N-取代苯基马来酰亚胺系列产物和反应过程的跟踪表征.通过研究产物和反应过程混合物的碳碳双键上质子、苯环上质子的化学位移和强度变化,判断反应进行程度.同时还研究了取代基对反应产物和中间产物的碳碳双键质子和苯环质子偶合常数的影响. 相似文献
9.
采用密度泛函(DFT)方法对八个中位有不同取代基的A3型corrole进行了几何结构优化和核磁共振(NMR)理论计算. 几何优化结果显示5,10,15-三苯基corrole的两个环内NH异构体的中位苯环空间排布方向不同. 此外, 虽然A3型corrole两个环内NH异构体A和B的能量相差不大, 但A和B分子的Boltzman分布概率却有较大的不同, 且受取代基影响很大. 因而在计算NMR时必须对A和B异构体的理论化学位移做Boltzman统计平均处理. NMR计算结果表明, 在B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d,p)水平下可以得到较为合理的corrole的1H-NMR化学位移结果. β-位氢的化学位移与取代基Hammett常数σ+P的大小成正比关系. 此外, 由于corrole大环的低对称性, 取代基对不同位置β-位氢的NMR影响程度不同, 其β-位氢化学位移的大小和顺序与中位取代基的电子效应和corrole的立体结构因素有关. 相似文献
10.
采用密度泛函(DFT)方法对八个中位有不同取代基的A3型corrole进行了几何结构优化和核磁共振(NMR)理论计算.几何优化结果显示5,10,15-三苯基corrole的两个环内NH异构体的中位苯环空间排布方向不同.此外,虽然A3型corrole两个环内NH异构体A和B的能量相差不大,但A和B分子的Boltzman分布概率却有较大的不同,且受取代基影响很大. 因而在计算NMR时必须对A和B异构体的理论化学位移做Boltzman统计平均处理.NMR计算结果表明,在B3LYP/6.311+G(2d,p)//B3LYP/6-31G(d,p)水平下可以得到较为合理的corrole的1H-NMR化学位移结果.β-位氢的化学位移与取代基Hammett常数σ-p的大小成正比关系.此外,由于corrole大环的低对称性,取代基对不同位置β-位氢的NMR影响程度不同,其β-位氢化学位移的大小和顺序与中位取代基的电子效应和corrole的立体结构因素有关. 相似文献
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Complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 3-(2-pyridyl)-1-(2-hydroxy phenyl)-2-propen-1-one (PHPO), 3-(1-naphthyl)-1-(2-hydroxy
phenyl)-2-propen-1-one (NHPO) and 3-(3,4-dimethoxy phenyl)-1-(2-hydroxy phenyl)-2-propen-1-one (DMPHPO) have been synthesized
and characterized by analytical, conductivity, thermal, magnetic, infrared, electronic and electron spin resonance data. Based
on analytical data the stoichiometry of the complexes has been found to be 1 : 2. The conductivity data show that all these
complexes are non-electrolytes. The infrared spectral data indicate that the ligand PHPO acts as uninegative tridentately
towards Co(II) and Ni(II) and bidentately with Cu(II), Zn(II) and Cd(II). Ligands like NHPO and DMPHPO act as uninegative
bidentately with all the metal ions. The electronic spectral data suggest that all the Co(II) complexes and Ni(II) of PHPO
complex are octahedral and all the Cu(II) and Ni(II) of NHPO and DMPHPO complex are square-planar. The complex of Zn(II) and
Cd(II) are tetrahedral. ESR parameters of Cu(II) complexes have been calculated and relevant conclusions have been drawn with
respect to the nature of bonds present in them. 相似文献
14.
Chlorofluorinate with Trifluoromethylhypochlorite CF3OCl. Preparation and Spectroscopic Characterization of Trifluormethyliodinechloridefluoride CF3I(Cl)F The preparation of a new iodine(III) compound, trifluormethyliodinechloridefluoride CF3I(Cl)F, via oxidative addition of trifluoromethylhypochlorite CF3OCl to trifluoromethyliodide CF3I is described. The thermolabile compound has been characterized by i.r., Raman, 19F NMR, and mass spectroscopy. 相似文献
15.
5,10,15,20-四(对氯苯基)卟啉羟基稀土配合物的光谱研究 总被引:8,自引:0,他引:8
研究了四(对氯苯基)卟啉及其羟基稀土配合物的紫外-可见光谱、红外光谱和拉曼光谱,对主要谱带进行了经验归属,讨论了中心离子对紫外光谱和共振拉曼光谱结构敏感带频率的影响. 相似文献
16.
Derivatives of Tricyanomethane. 2. Studies on Methyl Tricyanomethane (1,1,1-Tricyanoethane) The title compound H3C? C(CN)3 has been characterized by means of nuclear magnetic resonance, vibrational, and mass spectra. 相似文献
17.
Diffuse reflection FTIR spectral database of dyes and pigments 总被引:1,自引:0,他引:1
Silva CE Silva LP Edwards HG de Oliveira LF 《Analytical and bioanalytical chemistry》2006,386(7-8):2183-2191
24 pigments commonly used in art have been characterized by diffuse reflection infrared spectroscopy (DR). All of the compounds
have also been characterized by means of infrared absorption spectroscopy to demonstrate the reliability of the DR technique.
This is the first record of the use of this technique as an analytical tool in conservation science, and the results appear
to be promising for the identification of unknown pigments used on historical and artwork artifacts. Although the DR technique
used here is not nondestructive, it can still be usefully applied to the analysis of artwork since it requires only a very
small quantity of sample for analysis. 相似文献
18.
N.C.A. de Sousa M.T. de Araujo C. Jacinto M.V.D. Vermelho N.O. Dantas C.C. Santos I. Guedes 《Journal of solid state chemistry》2011,184(11):3062-3065
Optical and vibrational studies have been carried out on 60B2O3·(20−x)Na2O·10PbO·10Al2O3:xTiO2 (x=0, 1, 2, 3, 4, and 5 mol%) glasses, in order to understand the role of TiO2 in the 60B2O3·20Na2O·10PbO·10Al2O3 glass matrix. The X-ray patterns reveal homogeneous glasses over the entire compositional range. The absorption spectra show that the energy of the optical band gap (ΔEopt) and Urbach's energy (EU) decreases as TiO2 content increases. The changes observed in the Raman and IR spectra are related to the BO4→BO3 back conversion effect and the appearance of “loose” BO4− groups. The data indicate that titanium ions act as a network modifier. 相似文献
19.
V. A. Shlyapochnikov G. I. Oleneva N. O. Cherskaya O. A. Luk'yanov V. P. Gorelik O. V. Anikin V. A. Tartakovsky 《Russian Chemical Bulletin》1995,44(8):1449-1453
The vibrational and electronic spectra of dinitramide salts MN(NO2)2 (M=K, Na, Li, NH4, Fe, Ag, Mn, Mg, Rb, C(NH2)3) have been studied. The IR and Raman spectra of solutions and melts of the salts have been satisfactorily interpreted on the basis of the anion model withC
2v
symmetry. The complication of the spectra in the crystalline phase has been explained by restructurization of the anion that reduces its symmetry and makes the nitro groups nonequivalent.For part 6, seeIzv. Akad. Nauk, Ser. Khim., 1995, 113 [Russ. Chem. Bull.,44, 108 (Engl. Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1508–1512, August, 1995. 相似文献
20.
E. E. Laukhina Yu. M. Shul'ga V. I. Rubtsov V. N. Vasilets V. P. Bubnov E. B. Yagubskii N. V. Avramenko M. N. Frolova 《Russian Chemical Bulletin》1995,44(5):819-822
Crystals containing up to 30 wt. % CS2, according to the data of IR and X-ray photoelectron spectroscopy, were isolated from the C60-TSeT-CS2 (TSeT is tetraselenotetracene) system. The unusually high concentration of carbon disulfide results in the complete sublimation of the crystals at a relatively high temperature (520 °C). The electron energy loss spectra of the crystals obtained were measured and analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 845–848, May, 1995.This work was financially supported by the Russian Foundation for Basic Research (Projects No. 93-03-18002, 93-03-18705, and 93-03-5650). 相似文献