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81.
Chenxi Zhao Yingxu Zeng Mingzhu Wan Rongxi Li Yizeng Liang Chengyong Li Zhongda Zeng Foo‐Tim Chau 《Journal of separation science》2009,32(4):660-670
Systematic comparative research was conducted on essential oils from eight traditional Chinese medicines (TCM) of pungent flavor and cool nature because the essential oils are the main active ingredients of herbs of this kind. The work was based on their component analysis by gas chromatography–mass spectrometry (GC–MS), on their retention indices, as well as on chemometric resolution methods. A total of 144 compounds were tentatively identified, accounting for 69.0% to 91.8% of the total essential oils. It is worth noting that there are 67 compounds in at least three of these eight essential oils. Moreover, many biologically active compounds, such as hexanal, α‐pinene, camphene, β‐pinene, p‐cymene, limonene, eucalyptol, (Z)‐ocimene, γ‐terpinene, camphor, p‐menthone, 4‐terpineol, α‐terpineol, carvone, eugenol, caryophyllene, β‐farnesene, α‐curcumene, β‐selinene, δ‐cadinene, caryophyllene oxide, cedrol, n‐hexadecanoic acid, benzaldehyde, benzeneacetaldehyde, phthalic acid diisobutyl ester, linoleic acid, tetradecanoic acid, (Z,Z,Z)‐9,12,15‐octadecatrienoic acid, eucalyptol, pentadecanoic acid, hexadecanoic acid methyl ester, linoleic acid methyl ester, exist in at least four of the eight essential oils. These results might help us to understand why the eight herbs are all of pungent flavor and cool nature according to the theory of TCM, and may provide a useful chemical basis for future research on herbs of this kind. 相似文献
82.
Sie Tiong Ha Teck Ming Koh Guan Yeow Yeap Hong Cheu Lin Jun Kit Beh Yip Foo Win Peng Lim Boey 《中国化学快报》2009,20(9):1081-1084
A homologous series of Schiff base esters,6-methoxy-2-(2-hydroxy-4-alkanoyloxybenzylidenamino)benzothiazoles,comprising a benzothiazole moiety as the core was synthesized.All the members of this series exhibited an enantiotropic nematic phase. The azomethine linkage along with the lateral hydroxyl and terminal methoxyl groups were found to exert an effect on the mesomorphic properties. 相似文献
83.
84.
85.
Optical vortex coronagraph 总被引:1,自引:0,他引:1
We describe a method to observe dim exoplanets that eliminates light from the parent star across the entire exit pupil without sacrificing light from the planet by use of a vortex mask of topological charge m = 2. 相似文献
86.
A method that uses the quadrant photodiode has been shown to be relatively inexpensive and robust in measuring Gaussian laser beam diameters in two axes. This approach requires neither component rotation nor precision alignment, and it facilitates integration of Gaussian laser beam diameter measurement with laser beam tracking in instruments. The physical gap between sensors in the quadrant photodiode, however, limits laser beam diameter measurements to those in the millimeter range. Here, we describe a modified approach to measure Gaussian laser beam diameters that are significantly smaller. 相似文献
87.
Reactions of metal-metal bonded homobimetallic (Pd(2)) and heterobimetallic (PtPd) complexes, supported by a P,P'-bridging-bis(P,N-chelating) coordination mode of the potentially hexadentate ligand 1,1-bis[di(o-N,N-dimethylanilinyl)phosphino]methane (dmapm), with CO, diethylacetylenedicarboxylate (DEAD), and thiols (RSH) in CH(2)Cl(2) are described. At room temperature, rac-Pd(2)Cl(2)(mu-N,P:P',N'-dmapm) gives the stable complexes Pd(2)Cl(2)(mu-CO)(2)(mu-P:P'-dmapm) and PdCl(eta2-DEAD)(mu-P:P',N-dmapm)PdCl (which is fluxional in solution), while rac-PtPdCl(2)(mu-N,P:P',N'-dmapm) disproportionates to PtCl(2)(P,P'-dmapm) and Pd metal, although at low temperature intermediate carbonyl species are detected in the CO reaction. The reactions with thiols in the presence of triflic acid (HOTf) generate rac-[MPdCl(2)(mu-SR)(mu-N,P:P',N'-dmapm)][OTf] and H(2) for both M = Pt and Pd. In CH(2)Cl(2), PdX(2)(dmapm) species (X = halide or CN) exist as equilibrium mixtures of P,P'- and P,N-ligated forms. For X = Cl, the P,P'-P,N equilibrium is governed by DeltaH degrees = -5.5 +/- 0.5 kJ mol(-1) and DeltaS degrees = 10 +/- 1 J mol(-1) K(-1), and the ring-strain energy within the P,P'-isomer is approximately 32 kJ mol(-1); the equilibrium increasingly favors the P,N-form with X = CN > I > Br > Cl. The solid-state structures of rac-[PtPdCl(2)(mu-SEt)(mu-N,P:P',N'-dmapm)][OTf] and PdCl(2)(P,N-dmapm) are presented; the latter contains both bound and free N- and P-atoms of identical types in the same molecule and permits an assessment of sigma- and pi-bonding between these atoms and Pd. 相似文献
88.
Muhammad Kashif Erdawaty Jaafar Poonam Bhadja Foo Wah Low Siti Kudnie Sahari Shahid Hussain Foo Kai Loong Awais Ahmad Tahani Saad AlGarni Muhammad Shafa Humaira Asghar Saad A. Al-Tamrah 《Arabian Journal of Chemistry》2021,14(2):102953
This work investigated the effect of Potassium Permanganate (KMnO4) on graphene oxide (GO) properties, especially on electrical properties. The GO thin films were deposited on a glass substrate using drop casting technique and were analysed by using various type of spectroscopy (e.g. Scanning Electron Microscopy (SEM), Ultra- Violet Visible (UV–VIS), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), optical band gap, Raman Spectroscopy). Furthermore, the electrical experiments were carried out by using current–voltage (I-V) characteristic. The GO thin film with 4.5 g of KMnO4 resulted in higher conductivity which is 3.11 × 10?4 S/cm while GO with 2.5 g and 3.5 g of KMnO4 achieve 2.47 × 10?9 S/cm and 1.07 × 10?7 S/cm, respectively. This further affects the morphological (SEM), optical (band gap, UV–Vis, FTIR, and Raman), and crystalline structural (XRD) properties of the GO thin films. The morphological, elemental, optical, and structural data confirmed that the properties of GO is affected by different amount of KMnO4 oxidizing agent, which revealed that GO can potentially be implemented for electrical and electronic devices. 相似文献
89.
Daming Fan Enrique Meléndez Peng Foo Lee 《Journal of organometallic chemistry》2004,689(19):2969-2974
The acetonylgold(III) compound [Au(ppy)(CH2COCH3)Cl] (1) (ppy = 2-phenylpyridine) was unexpectedly obtained during the crystallization process of Au(III) lactate complex [Au(ppy)(CH3CHOHCOO−)Cl]. This new structure prompted us to further study the role of Au(III) complexes on the carbon-hydrogen activation of ketones. Complex [Au(ppy)(CH2COCH3)NO3] (2) was synthesized by reacting [Au(ppy)(NO3)2] with acetone while the ketonyl Au(III) complex [Au(apd)Cl2] (3) (Hapd = 2-acetylpyridine) was obtained through carbon-hydrogen bond activation of the acetyl group. The crystal structures of 1 and 2 have common features: a square-planar Au(III) centre coordinated by one five-membered chelate ring, one acetonyl ligand and one anion (chloride or nitrate). Both structures show that carbon-hydrogen activation of acetone by 2-phenylpyridine-Au(III) complexes leads to the formation of acetonyl-Au(III) complexes. The Au-CH2 bond lengths (2.067(7) Å, 1 and 2.059(5) Å, 2) are similar to each other but longer than the Au-C (phenyl) bond lengths. The two softest ligands (carbanion) are also cis to each other in the thermodynamically most stable isomer. In complex 3, the σ-bonded acetyl group is confirmed by 13C DEPT NMR spectroscopy. 相似文献
90.
Yip Foo Win Siang Guan Teoh Eng Khoon Lim Shea Lin Ng Hoong Kun Fun 《Journal of chemical crystallography》2008,38(5):345-350
Abstract The title compound, bis(2,4-dinitrobenzoato)tetrabutyldistannoxane(IV), was obtained from the reaction of di-n-butyltin(IV) oxide with 2,4-dinitrobenzoic acid. It crystallizes out as the usual dicarboxylatotetrabutyldistannoxane(IV)
dimer. In the monoclinic system P21/c, a = 12.391(3) ?, b = 19.937(5) ?, c = 15.026(4) ?, α = γ = 90°, β = 102.857(2)°, V = 3618.95(16) ?3 and Z = 2. A crystal structure determination of the title compound reveals the presence of a centrosymmetric planar Sn2O2, with two different environments for tin atoms and two distinct carboxylate groups. Two of the carboxylate groups are bonded
to the exocyclic tin atom in a bidentate bridging manner and the remaining two carboxylate groups are bonded to the tin atom
in a monodentate manner. As a result, both the tin atoms moieties in the complex are five coordinate and exhibit trigonal
bipyramid geometry.
Index Abstract Synthesis, Characterization and Crystal Structure of the Bis(2,4-dinitrobenzoato)tetrabutyldistannoxane(IV) Dimer
Yip Foo Win, Teoh Siang Guan, Lim Eng Khoon, Shea Lin Ng, Hoong Kun Fun
A crystal structure determination of the title compound reveals the presence of a centrosymmetric planar Sn2O2, with two different environments for tin atoms and two distinct carboxylate groups.
相似文献