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51.
Christopher Plant James E. Boggs John N. Macdonald Gwilym A. Williams 《Structural chemistry》1992,3(1):3-8
In this report the effects of basis set size and electron correlation on the internal rotation barrier heights in ethene thiol are investigated and compared with experimental data. At all levels of theory reasonable agreement is obtained for the barrier tosyn/anti rotation (experimental value: 9.6 kJ/mol), however, theanti barrier (experimental value: 0.14 kJ/mol) is consistently overestimated by approximately a factor of 10. A comparison of ab initio predictions of torsional energy distributions and rotational constant variations as a function of torsional state with the corresponding experimental quantities is presented. 相似文献
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53.
Two New Saponins from Lysimachia davurica 总被引:3,自引:0,他引:3
JingKuiTIAN ZhongMeiZOU LiZhenXU GuangHongTU HongWuZHANG ShiLinYANG DongGeAN 《中国化学快报》2005,16(2):212-214
Two new saponins named davuricoside I (1) and davuricoside E (2) were isolated from the whole plants ofLysimachia davurica. Their structures were determined by 1D and 2D NMR, FAB-MS techniques, and chemical methods. 相似文献
54.
Raymond J. Abraham James Plant Geoffrey R. Bedford 《Magnetic resonance in chemistry : MRC》1982,19(4):204-210
The preparation, isolation and characterization by proton and 13C NMR of the four possible atropisomers of meso-tetra(2-methoxy-1-naphthyl)porphyrin is described. Chemical shift differences due to atropisomerization effects are observed in the porphyrin and naphthyl rings. Comparison of the naphthyl chemical shifts with those of the model compound 1-isopropenyl-2-methoxynaphthalene allows the shifts due to the porphyrin ring current to be isolated. The observed Δδ values of the naphthyl protons agree well with those calculated from the previously described porphyrin ring current model, and allow both the angle of tilt of the naphthyl ring and the dihedral angle of the 2-methoxy substituent to be estimated. In contrast, the Δδ values for the naphthyl carbons bear no relationship to the calculated ring current shifts. Calculations of the total ring current contribution (porphyrin plus naphthyl rings) at the different naphthyl rings of the unsymmetric type III isomer show that at least part of the observed atropisomerism effects are due to the long-range current shifts of the naphthyl rings. The results also provide a clear demonstration of the identity of the porphyrin ring current in the free base and porphyrin dication. 相似文献
55.
H. Heller H. Clever G. T. Piercy E. K. Plant M. C. Rogers S. Zweig A. Taub J. D. White F. W. Rose Jr. und K. S. Nitsche 《Fresenius' Journal of Analytical Chemistry》1943,125(1-2):66-68
Ohne Zusammenfassung 相似文献
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Xing Li Zhang Yang Yang Liu Jian He Wei Yun Yang Zheng Zhang Jun Qing Huang Huai Qiong Chen Yu Jun Liu 《中国化学快报》2012,23(6):727-730
We used whole-tree agarwood-induction technology to produce agarwood from Aquilaria sinensis trees within 20 months,and evaluated the quality of this agarwood.The results showed its characteristics were similar to those of high-grade wild agarwood in terms of texture,chemical constituents,essential oil content,and ethanol-soluble extract content,with the lattermost quality far surpassing the requirement of traditional Chinese medicine agarwood,as indicated in Chinese Pharmacopoeia 2010.To the best of our knowledge,this is first study to show that high-quality agarwood can be produced in whole A.sinensis trees via a chemically induced technology. 相似文献
58.
JianXinCAO GuoFangLAI YiFengWANG YuanFengHUANG ShiDeLUO 《中国化学快报》2004,15(7):791-793
A new sesquiterpenoid was obstained from the leaves of Magnolia delavayi. Its structure was determined as 8β-acetoxy-10α-ethyloxy-guaia-4α, 11-diol on the basis of spectral evidence. 相似文献
59.
LV YongJun XU Jian GUO Yong & SHAO ShiJun Key Laboratory of Chemistry of Northwestern Plant Resources Key Laboratory for Natural Medicine of Gansu Province Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou China State Key Laboratory for Oxo Synthesis Selective Oxidation China Graduate University of the Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2011,(5)
A boradiazaindacenes (BODIPY)-phenol conjugate,1,can act as a colorimetric and fluorometric sensor for sensitive and se-lective measurement of F-over AcO-and H2PO-4 in CH3CN. Sensor 1 gives response to F-in a 1:1 ratio via the deprotonation of the phenolic OH proton,which results in color change from pale yellow to light green and quenching of bright green fluo-rescence. 相似文献
60.
Ab initio calculations with complete geometry optimisation have been used to study internal rotation in compounds of the type XCH = CHSH, X = CN, H, CH3 and F, with X located trans to the sulphur atom. Potential functions for the CS torsion have been obtained for each case and it has been established that the dominant framework changes accompanying internal rotation in these molecules involve the CCS angle and CS bond length. Furthermore, it has been shown that the nature of the substituent X significantly affects the molecular conformation of the SH group. The observed trends are discussed in terms of a simple model. 相似文献