共查询到20条相似文献,搜索用时 78 毫秒
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南蛇藤中倍半萜生物碱的二维NMR研究 总被引:1,自引:0,他引:1
用DEPT和二维NMR技术包括:1H-1H COSY,1H-13C COSY,NOESY,特别是1H-13C COLOC对两个多酯基取代的倍半萜生物碱的化学及立体结构进行了研究,并对其1H和13C NMR谱峰进行了归属。 相似文献
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乙基紫苏霉素硫酸盐的选择性远程DEPT和二维NMR研究 总被引:1,自引:1,他引:0
本文通过选择性远程DEPT和二维NMR实验研究了由紫苏霉素合成的乙基紫苏霉素硫酸盐的1H和13C NMR谱,推定其结构为(1),并且对其NMR谱峰归属作了确定。 相似文献
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α,α'-二氧代烯酮环二硫代缩醛的NMR研究 总被引:4,自引:3,他引:1
报道了7种新的α,α'-二氧代烯酮环二硫代缩醛化合物的NMR谱.应用1H、13C NMR谱等确定了这7种新化合物的分子结构,并对全部谱峰进行了归属,初步探讨了分子结构对化学位移的影响. 相似文献
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测定了丙酮肟在四氯化碳、氯仿、二氯甲烷、苯和甲苯溶剂中随丙酮肟摩尔浓度变化的1H NMR谱,观察到在氯代甲烷溶剂中,丙酮肟分子中两个甲基和氯代甲烷的质子共振峰随丙同肟摩尔浓度增加而逐渐移向高场,而羟基共振峰却逐渐移向低场。其两个甲基表现为单峰。在芳烃溶剂中,丙酮肟分子中两个甲基和芳烃质子共振峰随丙酮肟摩尔浓度增加逐渐移向低场,且两个甲基表现为双峰,得到了所有化学位移与丙酮肟摩尔浓度呈线性关系。 相似文献
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The π-bond model is applied to the calculation of the proton chemical shifts of a range of benzenoid hydrocarbons. The simple calculations give results which compare well with experiment and with calculations based on the ring current model. Least squares fitting of the predicted chemical shifts to the observed values can give an indication of the occurrence of local aromatic groups in larger molecules. This procedure also yields an empirically adjusted estimate of the anisotropy in the molar magnetic susceptibility from the experimental proton chemical shifts. A simple criterion for aromaticity is also given. The overall results suggest that there is no need to associate a special ring current attribute to π conjugation in aromatic molecules. 相似文献
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The carbon chemical shifts of pyridine associated to various aliphatic and aromatic alcohols are measured. Actual effects of hydrogen bonding formation on 13c shifts, have been characterized by evaluating in first, anisotropy and non specific medium effects. Linear relationships are obtained between 13C shifts and the IR frequency shifts. Positive slopes are observed for C-β and C-γ in agreement with the electron population change, but a reverse slope results for C-α carbon. 相似文献
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本文测定了三个3(或4)-取代苯甲亚氨酸乙酯(1)和八个N-氰甲基-3(或4)-取代苯甲亚氨酸乙酯(2)的~(13)C-NMR谱。归属了1 和2和各碳化学位移。求得了的取代基化学位移(substituent Chemical Shift,SCS)。碳-13化学位移与单取代苯的取代基化学位移(SCS)的相关分析表明:4-取代苯甲亚氨酸酯1 b~g和2b~e中,除C_(2,6)外,其他各芳碳的化学位移值与加和规则基本相符;3-取代苯甲亚氨酸酯1h~j和2f~h中,除C_1外,其他各芳碳的化学位移值与加和规则基本相符。另外,本文还进行了碳-13化学位移与σ_(I)/σ_(R)~O和F/M的双参数相关分析。 相似文献
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Kwok CW Ho CN Chi LM Lam SL 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,166(1):11-18
The sequence and temperature effects on random coil DNA carbon chemical shifts have been investigated using sixteen 17-nucleotide sequences. Temperature effect correction parameters have been determined for the aromatic C6/C8 carbons and the deoxyribose C1', C2', and C3' carbons. The carbon chemical shifts of a specific nucleotide in a random coil sequence have been shown to depend mainly on the type of its nearest neighbors. A carbon chemical shift database containing all 64 different types of triplets has been established for predicting random coil DNA carbon chemical shifts. The use of this triplet database for carbon chemical shift predictions shows good accuracy with experimental data, with root-mean-square deviations of 0.09, 0.10, 0.10, and 0.10 ppm and correlation coefficients of 0.999, 0.996, 0.978, and 0.974 for C6/C8, C1', C2', and C3', respectively. 相似文献
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Lev R. Ryzhkov 《光谱学快报》2013,46(5):1089-1096
1H-NMR spectra of DBH (1), DBO (2) and of the synthetic precursor to 1, 1,4-phenyl-2,4,6-triazatricyclo[5.2.1.02,6]heplanc-3,5-dione (3), were recorded in acetone-d6 and C6D6 at 500 MHz. Assignment was aided by complete resolution of signals of 1 and 3 in C6D6 by aromatic solvent-induced shifts (ASIS). The effect of the change from phenyllriazolinedione to a diazene functional group on the chemical shifts of the exo,endo and syn,anti protons was investigated. The chemical shifts of the exo,endo protons of 1 are exceptionally sensitive to the functional group at the hetero substituted bridge in the DBH skeleton. However, the relative chemical shift of the syn,anti proton pair is independent of the nature of the functional group. The role of stereochemical effects on these chemical shifts is discussed. 相似文献
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Angelika Baranowska-Łączkowska Krzysztof Z. Łączkowski Manuel Vilas-Varela Sara Collazos 《Molecular physics》2017,115(17-18):2201-2208
ABSTRACTUsing computational chemistry methodology, we evaluate the proton magnetic shieldings and the corresponding chemical shifts of 12 polycyclic aromatic hydrocarbons that derive from chrysene, perylene and picene. Due to the large size of the studied compounds, we resort to density functional theory (DFT) and use it together with the B3LYP and the KT1 functionals. After a systematic method and basis set selection study carried out on methane, benzene and anthracene, the DFT(B3LYP) method and the 6-31G*, 6-31G** and 6-311++G** bases are selected to carry out the calculations, because of the efficiency in providing shifts close to the experimental data available. Additionally, we select the DFT(KT1) method together with the aug-pcS-1 basis set, and HF/6-31G* shifts are also calculated. In order to estimate the error in the theoretical results, we take as reference accurate experimental chemical shifts obtained for the molecules under investigation. Extra measurements are needed for this purpose and are included in the present work. The best combination of method and basis set is DFT(B3LYP)/6-31G**, proving to be very efficient in getting shifts close to experiment at a relatively low computational cost, and therefore we recommend it for the evaluation of proton shifts in larger polycyclic aromatic hydrocarbons. 相似文献
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三环已基羧酸锡的13C和119Sn NMR研究 总被引:2,自引:2,他引:0
测定了33个三环己基脂肪族和芳香族羧酸锡在非配位溶剂(CDCl3)中的13C和119Sn NMR谱。结果表明:化学位移δ(119Sn)值主要由锡原子的配位数决定,结构上微小的变化。都能在δ(119Sn)值上明显地表现出来。讨论了不同类型化合物间NMR参数间的关系。 相似文献
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Dachraoui H Michelswirth M Siffalovic P Bartz P Schäfer C Schnatwinkel B Mattay J Pfeiffer W Drescher M Heinzmann U 《Physical review letters》2011,106(10):107401
A time-resolved study of core-level chemical shifts in a monolayer of aromatic molecules reveals complex photoinduced reaction dynamics. The combination of electron spectroscopy for chemical analysis and ultrashort pulse excitation in the extreme ultraviolet allows performing time-correlated 4d-core-level spectroscopy of iodine atoms that probe the local chemical environment in the adsorbate molecule. The selectivity of the method unveils metastable molecular configurations that appear about 50 ps after the excitation and are efficiently quenched back to the ground state. 相似文献