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101.
Total synthesis of (-)-lentiginosine was achieved from D-mannitol using highly stereoselective reactions. Similarly, (+)-lentiginosine was synthesized from L-tartaric acid. 相似文献
102.
Self-assembled multilayer thin films have been prepared on Au substrate by alternate surface derivatization with L-cysteine hydrochloride and cupric perchlorate. The layer-by-layer structure at each step of multilayer formation was investigated by X-ray photoelectron spectroscopy. The measurements indicate that there are two structure modes in the multilayers. One is that Cu(2+) sandwiches between two amino acid groups. The other one is that Cu(+) is bonded through disulfide and thiolate. This process is also confirmed by cyclic voltammetry of Cu ion at different self-assembled multilayers. Steps further on will lead to repeated multilayer films. 相似文献
103.
Bjelopavlic M Singh PK El-Shall H Moudgil BM 《Journal of colloid and interface science》2000,226(1):159-165
Hydrogen bonding is generally thought to be an ubiquitous adsorption mechanism, which often foils selective adsorption schemes. Through investigation of hydrogen bonding energy and its dependence on surface molecular architecture, it may be possible to develop new methodologies to control the adsorption of surfactants and polymeric flocculants, depressants, and dispersants used in particulate processing industries. A model system using St?ber silica spheres and polyethylene oxide, a polymer known for its ability to form hydrogen bonds, was examined. The effect of two different surface treatments of the silica particles, calcination and rehydroxylation, upon the adsorption of two polymer molecular weights was studied. The adsorption behavior was then linked to the respective surface structures via characterization of the surfaces using FTIR, NMR, and Raman techniques. In this paper role of hydrogen bonding sites and surface architecture on adsorption is discussed. Copyright 2000 Academic Press. 相似文献
104.
Attempts to cyclise o-chlorophenyl benzyl ether, sulphide, sulphoxide and sulphone by treatment with KNH2/NH3 were unsuccessful. Similar reaction of 1-(o-chlorophenyl)-2,2-diphenylethane led to amination whereas α-(o-chlorobenzyl)phenylacetic acid gave a dihydrocoumarin. Reaction of 4- and 2-(o-chlorophenethyl)-pyridines, however, afforded products comprising benzisoquinolines and 1-pyridylbenzocyclobutenes. 相似文献
105.
106.
The dielectric constant ?' and loss tangent tan δ of chlorobenzene-cis-decalin mixtures have been measured in the temperature range 77 K to 330 K and frequency range 0.1 to 100 kHz. On cooling, ?' increases with decreasing temperature upto about 135 K, after which it drops rapidly with decreasing T followed by a slow decrease. This indicates that the liquid mixture goes to an amorphous phase which transforms to a glass phase of restricted dipole rotation below Tg; however, the peak in ?' is due to relaxation in the amorphous phase (α relaxation) and does not give an exact Tg. On heating, the behaviour of the cooling curve is retraced upto 160 K, after which ?' drops suddenly to a value lower than that at 77 K in the glass phase. This indicates the transition to a crystalline phase in which dipole rotational freedom is completely lost. The crystalline phase changes to a eutectic liquid phase of high ?' at a temperature (200 K) lower than the melting point of chlorobenzene and cis-decalin. Dielectric dispersion is observed only in the glass and amorphous phases. The dielectric relaxation time is independent of the concentration of chlorobenzene. 相似文献
107.
Prakash O Kaur H Batra H Rani N Singh SP Moriarty RM 《The Journal of organic chemistry》2001,66(6):2019-2023
The combination reagent (dichloroiodo)benzene and lead(II) thiocyanate in dichloromethane effects oxidation of various enol silyl ethers, ketene silyl acetals, and beta-dicarbonyl compounds, thereby providing an efficient and convenient method for alpha-thiocyanation of carbonyl and beta-dicarbonyl compounds. 相似文献
108.
Trimethylsilyldiethylamine Me3SiNEt2 and MoOCl4 (1:1) undergo a free radical redox reaction in CH2Cl2 or Et2O to form MoCl3O(HNEt2). Reduction occurs even in aprotic media like CCl4 and CS2 to give MoV complexes Mo2Cl6O2(N2Et4) and Mo2Cl6O2[(SCNEt2)2S2], respectively. A 2:1 reaction in nonionizing protic solvents undergoes redox cum cleavage to provide MoCl2O(NEt2) (HNEt2) but a reaction at reflux temperature in 1,2-dichloroethane leads to diethylammonium salt, [Et2NH2][MoCl4O(HNEt2)]. Higher molar reactions (3:1, 4:1) in CH2Cl2 or Et2O are associated with redox reaction as well as oxygen atom abstraction to form de-oxo MoIV complex MoCl3(NEt2)(HNEt2)2, whereas, a 3:1 reaction in CS2 forms Mo2Cl4O(S2CNEt2)4. Compounds have been characterized by elemental analyses, redox titration, magnetic moment, conductance, infrared, electronic absorption and 1H-NMR measurements. 相似文献
109.
Synthesis of cis-hydrindane analogues (2,3) of Cecropia juvenile hormone-I from common intermediate cis-hydrindane-2, 5-dione is presented. The analogues are only moderately active against Dysdercus cingulatus. 相似文献
110.
R. P. Rastogi Kehar Singh Ram Shabd B. M. Upadhyay 《Journal of colloid and interface science》1981,80(2):402-411
Electrical properties of cholesterol interfaces have been investigated. For this purpose electroosmotic and hydrodynamic permeation of water, sodium chloride, barium chloride, aluminum chloride, and urea solutions across a cholesterol plug have been investigated. Dependence of electroosmotic permeability on concentration of electrolytes has also been studied. Electrophoretic mobility of cholesterol particles of known size distribution and dispersed in solutions of varying concentrations of electrolytes and urea has also been studied. The data have been used to estimate ζ potentials in order to have a plausible picture of the electrical double layer at the cholesterol/ solution interfaces. 相似文献