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111.
Orientational order parameter S is evaluated in the nematic phase of six liquid crystal compounds, N-(p-n-propyl benzylidene)-p-n-alkoxy anilines, 3.Om and N-(p-n-propyloxy benzylidene)-p-n-alkoxy anilines, 3O.Om compounds with m = 6, 7 and 8, using different methods. The techniques employed are S from birefringence δn, Haller's approximation from (1?T/Tc) β, effective geometry parameter αg and Vuks’ scaling factor SC. The values of S obtained using the above methods are compared with one another and with the results on a number of liquid crystals; the liquid crystals favor isotropic Vuks’ method. 相似文献
112.
Mamta Chauhan 《Phase Transitions》2015,88(12):1193-1212
The structural, electronic, mechanical, phase transition, and thermo-physical properties of refractory carbides, viz. VC, NbC, and TaC have been computed in stable B1 and high pressure B2 phases by means of two different ab initio calculations using pseudo- and full-potential schemes. These materials have mixed covalent-, metallic-, and ionic-type bonding. The calculations of elastic constants show the mechanical stability of these materials in B1 phase only. The brittle nature and anisotropy is observed in these materials in B1 phase. Non-central forces are present in both the phases. Elastic wave velocities and Debye temperature have also been calculated. The present results on structural, phase transition, elastic, and other properties are in reasonably good agreement with the available experimental and theoretical data. The calculations in high pressure phase need experimental verification. 相似文献
113.
114.
Ali Deeb 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):637-650
AbstractThis review describes the synthesis and reactions of 5-aminothieno[2,3-c]pyridazine-6-carbonitriles as a building blocks for the synthesis of polyfunctionalized heterocyclic compounds. The antimicrobial activity of some compounds are discussed. 相似文献
115.
Abdollah Javidan A. R. Banan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2253-2258
The synthesis of dialkyl-(2,2,2-trichloro-1-Hydroxyethyl) phosphonates using dialkyl hydrogen phosphite and chloral hydrate under solvent-free condition by microwave irradiation is reported. The products were chrachetrized using 1 H NMR, 13 C NMR, and 31 P NMR spectroscopy. 相似文献
116.
L. Engman A. Wojtoń B. J. Oleksyn J. Śliwiński 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):285-292
The crystal structure of 2-[N,N-dimethylamino)methyl]benzenetel-lurenyl chloride (2), a compound previously formulated as bis[[2-(N,N-dimethylamino)methyl]phenyl] ditelluride bis hydrochloride (1a), was determined. In the molecule 2, tellurium is bonded to the carbon of the phenyl group [2.120(3) Å], the nitrogen of the ortho dimethylamino substituent [2.362(3) Å], and the chlorine atom [2.536(1) Å]. There also is an intermolecular interaction of the tellurium atom with the phenyl ring of a neighbouring molecule [3.655(1) Å], resulting in the formation of zigzag chains along the b axis. The noncentrosymmetric space group of the crystal can be explained by the chiral surrounding of tellurium. 相似文献
117.
The influence of cyclodextrins (CDs) on the formation of azocrown ethers comprising pyrrole, imidazole and substituted imidazole has been studied. Pyrrole, imidazole, 2-methyl-, 4-methyl- and 4-phenylimidazole were coupled with bis-diazonium salts derived from bis-1,5-(2-aminophenoxy)-3-oxapentane or bis-1,8-(2-aminophenoxy)-3,6-dioxaoctane to form macrocyclic compounds with two azo units. The syntheses were performed under standard conditions in the presence of α-, β- or γ-CDs and the yield of the reaction products was compared with the results of plain experiments, i.e. without CDs. The results are discussed in terms of co-conformation of azole molecules embedded in CD cavity. Pyrrole or imidazole or imidazole derivatives were coupled with bis-diazonium salts to form macrocycles with two azo units. The syntheses were performed under standard conditions in the presence of α-, β-, or γ-cyclodextrin and the yield of the reaction products was compared with the results of plain experiments, i.e. without CDs. The results are discussed in terms of co-conformation of azole molecules embedded in cyclodextrin cavity. 相似文献
118.
Inclusion compounds were formed with 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol (H) and carbon tetrachloride, chloroform, dichloromethane and acetonitrile. 1 (H·1/2CCl4), 2 (H·1/2CHCl3) and 3 (H·1/2CH2Cl2) are true clathrates with the guest molecules situated in cages created by the host. 4 (H·2CH3CN) exhibits a different packing arrangement with the guest molecules located in channels. The crystal structures and stability of these inclusion compounds were investigated. 相似文献
119.
Qixin Dong Jiajun Zhu Qiang Sui Chao Tang Xiaomei Wang Yunqiu Yu 《Journal of separation science》2013,36(7):1200-1208
In this study, the objective was to investigate the degradation behavior of Esomeprazole under different recommended stress conditions according to International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use [1] by HPLC. Our research showed that the effect of mobile phase species on separation was significant for the determination of Esomeprazole and its related compounds. Successful separation of the drug from its related impurities and degradation products formed under different stress conditions was achieved using ammonium acetate buffer/ACN by a gradient elution. Compared with phosphate buffer/ACN, ammonium acetate buffer/ACN under same pH and gradient showed a great improvement in resolution due to the change of elution order. The drug was subjected to stress conditions including acidic, alkaline, oxidative, photolytic, and thermal conditions. Extensive degradation occurred in acidic and oxidative conditions, while mild degradation was observed in alkaline and photolytic conditions. Besides, it turned out the drug was extremely stable under thermal condition. The stability‐indicating LC–UV method was validated with respect to linearity, precision, accuracy, specificity, and robustness. The LC–MS method was also adopted for the characterization of degradation products. Based on the m/z values and fragmentation patterns, the degradation pathway of the drug has been proposed. 相似文献
120.
2-Acyltetrahydro-β-carbolines 7 have been obtained by cyclization of adducts 5 from imines 3 of tryptamine 1 and aldehydes 2 with acyl chlorides 4 as a result of an intramolecular a-amidoalkylation reaction in the presence of bases as N,N-dimethylaniline or Et3N. 相似文献