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研究了In(Ⅲ)和Y(Ⅲ)-1,2-丙二胺四乙酸配合物 ̄1HNMR谱的温度依赖性,其结果显示出8个乙酸质子处于不同的磁环境中,分4组AB谱。AB谱交换现象由氮原子翻转引起,通过全线型分析求得了速率常数及相关热大学参数。对不对称的氮原子,其翻转速率不同,靠近CH_3─基团的氮原子翻转速率要比远离CH_3─的小.活化能与金属离子的离子势呈线性关系。 相似文献
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Keum SR Roh HJ Choi YK Lim SS Kim SH Koh K 《Magnetic resonance in chemistry : MRC》2005,43(10):873-876
(1)H and (13)C NMR spectra of symmetric and asymmetric bis-spiropyrans, Series 1-3, were completely assigned. Especially, the (1)H assignment of asymmetric spiropyrans was achieved by utilizing (1)H-(1)H COSY and nOe experiments. All of the carbons in the dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR), together with an attached proton test (APT). 相似文献
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该文用完全线形分析法、磁化强度迁移法和自选锁定技术等三种具体的DNMR法对含有不同取代基的金属烯烃有机化合物中因碳碳键转动引起的分子内质子的化学交换的动力学行为进行了较为详细的研究。结果表明,测得的化学交换的速率常数是合理的。它们满足Eyring 和Ar-rehenuius 关系式;由此获得的化学交换的活化能参数和活化自由能的变化与化合物中的取代基的Hammett 常数6存在很好的一致关系。 相似文献
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S. G. Sakharov N. I. Pakuro A. A. Arest-Yakubovich L. V. Shcheglova P. V. Petrovskii 《Journal of organometallic chemistry》1999,580(2):2283
Mixtures of 2-ethylhexylsodium and 2-ethylhexyllithium are studied by 1H- and 13C-NMR spectroscopy in the temperature range from 20 to −50°C in hydrocarbon solutions. Characteristic temperature-dependent spectra obtained are indicative of dynamic exchange processes taking place in the system. The following activation parameters are found: ΔH≠=31.7±2.7 kJ mol−1; ΔG≠313=58.7±0.6 kJ mol−1; ΔS≠=−86.37±10.8 J mol−1 K−1. The negative value of the activation entropy indicates that the exchange proceeds through the associative mechanism. The participation in exchange reactions of aggregates, containing both sodium and lithium derivatives, is suggested. 相似文献
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用核磁共振波谱仪测定了Mg、Ca、Sr和Ba-PDTA络合物分子在一定温度时的~1H-NMR谱。通过对这些谱线的定性分析和定量研究得到了一些新的结果,求出了Ca和Mg-PDTA络合物的在不同温度时的分子内交换的速率常数和活化参数,并对这些结果进行了讨论。 相似文献
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By means of a base-catalysed ring enlargement of triazapentalenoindenes resulting from diasteroselective anhydride-induced ring transformation of chiral aminoalcohol-derived zwitterionic 2,3-dihydroimidazo[2,1-a]phthalazinium-olates, a series of pyrazolo[1,5-d][1,4]diazocin-7(6H)-ones with central and conformational chirality were obtained in enantiomerically pure form. The possible reasons of the characteristic substrate- and reagent-dependency observed for the diasteroselective ring transformations of the zwitterions were interpreted in terms of the relative energetics of the crucial alternative imidazolinium intermediates disclosed by B3LYP/6-31G(d,p) calculations. The trans-annular opening of three epimeric pairs of triazapentalenoindanones afforded identical pyrazolodiazonine products. This finding suggests that the primarily formed diastereomers, having different asymmetric conformations but the same element of central chirality, undergo ring inversions in one- and two steps, respectively, involved in pathways previously established for the facile racemisation of pyrazolodiazocines with conformational chirality and hydrogen- or methyl-substituent at C1-position. The ring enlargement of triazapentalenoindanones resulted from butyric anhydride-mediated ring transformation of zwitterions with symmetrical substitution pattern afforded highly rigid 1-ethylpyrazolodiazocines in racemic form potentially separable without thermal racemisation. The constitution, conformation and relative configuration of the novel compounds were determined by 1H-, 13C- and 15N-NMR methods including 2D-HSQC, 2D-HMBC and DNOE measurements and the structure of a pyrazolodiazocine was supported by single crystal X-ray diffraction. 相似文献
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以7-羟基香豆素为原料,经过Mannich反应化学选择性地得到了8位的7-羟基香豆素Mannich碱,然后在三乙胺存在的条件下,与磷酰二氯氮芥发生环合反应得到了一种新型的香豆素-7,8-环磷酰胺衍生物. 通过中间产物Mannich碱和目标产物的NMR图谱,都证实了Mannich反应的化学选择性位点是7-羟基香豆素的8位而不是6位;通过DEPT、1H-1H COSY,HSQC和HMBC等2D NMR技术对目标化合物的1H 和13C NMR数据进行了全归属和较详细的解析. 相似文献