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chair-form
相关语句
  相似匹配句对
     On form
     “形式”论
短句来源
     Chair
     椅子
短句来源
     Study on Form Design of Ming-style Chair
     明式家具中椅的造型艺术研究
短句来源
     Li form.
     Li,form.
短句来源
     Wits in the Chair
     椅中的智慧——意大利坐椅设计欣赏
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In this article, INDOR method was used to monitor the multiplets of the anome ric protons and the hydroxyl protons of four monosaccharides. The individual peaks of the C_2~C_4 protons in the overlapped multiplets were detected indirectly to obtain the NMR parameters—chemical shift δ and coupling constant J. By means of the Karplus equation, the orientations of all the C—H bonds were determined. The configurations and conformations of these sugars derived from INDOR are as follows: β-L-arabinopyranose chair form...

In this article, INDOR method was used to monitor the multiplets of the anome ric protons and the hydroxyl protons of four monosaccharides. The individual peaks of the C_2~C_4 protons in the overlapped multiplets were detected indirectly to obtain the NMR parameters—chemical shift δ and coupling constant J. By means of the Karplus equation, the orientations of all the C—H bonds were determined. The configurations and conformations of these sugars derived from INDOR are as follows: β-L-arabinopyranose chair form (~4C_1); α-L-rhamnopyranose chair form (~1C_4); α-D-xylopyranose chair form (~4C_1); α-D-and β-D-mannopyranose chair form (~4C_1).

本文用核磁共振谱的INDOR,研究若干单糖在DMSO溶液中的构型和构象。在单糖分子中,除少数质子如差向异构氢(C_1—H)外,大多数质子处于相似的化学环境中,相邻者又彼此偶合,在常规核磁共振谱上产生的信号重迭交错,形成峰包,无法一一辨认以确定归属。从木糖、阿拉伯糖、甘露糖、鼠李糖等单糖在DMSO中的1NDOR谱,可间接测得C_2~C_4上质子的各组谱线,进而获得每一质子的化学位移及偶合常数。用Karplus方程定出相邻碳上质子的两面角及C—H键取向,因而确证这些分子在DMSO中的立体结构。

An EHMO calculation has been performed for 2,2,6,6-tetramethyl-4-hydroxypiperidine-l-oxyl(TMHPO). It is shown that the most stable conformation is the chair form with a 12° of “out of plane” angle between the C-N-C plane and the N-O bond, which is consistent with that obtained by X-ray diffraction. The colouration of the nitroxide and the spectroscopic bands of TMHPO in u. v. -visible spectrum may be explained by analyzing the MO levels. The spin density on the nitrogen atom is estimated to be 0.43, from which...

An EHMO calculation has been performed for 2,2,6,6-tetramethyl-4-hydroxypiperidine-l-oxyl(TMHPO). It is shown that the most stable conformation is the chair form with a 12° of “out of plane” angle between the C-N-C plane and the N-O bond, which is consistent with that obtained by X-ray diffraction. The colouration of the nitroxide and the spectroscopic bands of TMHPO in u. v. -visible spectrum may be explained by analyzing the MO levels. The spin density on the nitrogen atom is estimated to be 0.43, from which the ESR hyperfine splitting constant is calculated to be 10.8 G,which is in good accordance with the experimental value.

用EHMO法对2,2,6,6-四甲基-4-羟基哌啶-1-氧(TMHPO)作了量子化学计算,计算出分子的平衡构象为椅式构象,并应具有12°的“离平面”夹角,与实验测定的构象符合;对分子轨道能级的分析说明了TMHPO具有颜色的原因,并指出了可见—紫外光谱图上两个吸收带的性质;根据对未成对电子自旋密度的计算得出ESR超精细分裂常数为10.8G,与实验值符合的较好。

The chemical structure of Bao Gong Teng A, a new myotic agent isolated from the stem of Chinese medicinal plant Bao Gong Teng (Erycibe obtusifolia Benth.), has been determined by the analysis of ~1H and ~(13)C NMR and high resolution MS data of Bao Gong Teng A and its derivatives. The functional groups present in the molecule of Bao Gong Teng A are a secondary amino group, a secondary alcoholic group and an acetoxy group. No double bond is present. By comparing the MS and ~1H NMR data of its N-methyl derivative...

The chemical structure of Bao Gong Teng A, a new myotic agent isolated from the stem of Chinese medicinal plant Bao Gong Teng (Erycibe obtusifolia Benth.), has been determined by the analysis of ~1H and ~(13)C NMR and high resolution MS data of Bao Gong Teng A and its derivatives. The functional groups present in the molecule of Bao Gong Teng A are a secondary amino group, a secondary alcoholic group and an acetoxy group. No double bond is present. By comparing the MS and ~1H NMR data of its N-methyl derivative to those of the authentic samples of 3α-and 3β-isomers of 6β-acetoxy-3-tropanol, it is certain that the molecule has nortropane skeleton with a 6β-acetoxy group. The position of the hydroxyl group can be assigned to C-2 by using the double resonance techniques in ~1H NMR of its N-methyl acetyl derivative. Furthermore, according to the base widths of proton signals the steric orientation of C-2 OH is possible only if it assumes a β-configuration in the favored chair form of piperidine. Consequently, the chemical structure of Bao Gong Teng A is represented as 2 β-hydroxy-6β-acetoxy-nortropane with a levorotation [[α]_D~(28) =-7.21 (C 0.97, H_2O)]. The explanation of all the principal fragments in its high-resolution mass spectra by such a structure is satisfactory.It is noteworthy that a strong myotic property is associated with the structure of natural tropane alkaloids of which some are known to have opposite mydriatic property and, to our knowledge, the structure and functions of Bao Gong Teng A have not been reported in the literature. This finding may have significance in the study of receptor theory in pharmacology.

本文报道草药包公藤(Erycibe obtusifolia Benth.)茎中新缩瞳有效成分包公藤甲素C_9H_(15)O_3N的结构研究。通过甲素及其衍生物的化学反应、~1H和~(13)CNMK、MS测定,证实甲素具有去甲莨菪烷的母核并连有6β-乙酰氧基。通过对N-甲基化甲素乙酰化物~1H NMR双照射去偶测定,确定羟基位于2β。最后推断甲素的结构应为2β-羟基-6β-乙酰氧基去甲莨菪烷,并经高分辨MS加以验证。结合[α]的测得,天然甲素为左旋体。

 
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