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81.
Thiolate self-assembly on gold has proven to be a valuable technique for assembling monolayers on a wide variety of substrates. However, the oxidative instability of the thiols, especially aromatic thiols and alpha,omega-dithiols, presents several difficulties. Shown here is that thiocyanates, easily synthesized stable thiol derivatives, can be directly assembled on gold surfaces with no auxiliary reagents required. Assembly is complete in 24 h and leaves a similar gold thiolate structure as seen in typical thiol self-assembled monolayers. 相似文献
82.
Contributions to the Chemistry of Organo-Transition Metal Compounds. 47. Reactions of Hexachlorocerates(IV) with Organolithium Compounds Pyridinium hexachlorocerate(IV) reacts with lithium organyls RLi RLi (R = 1-Nor, (CH3)2NCH2CH2CH2, n-C4H9) in the molar ratio 1:2 with formation of Li2[CeCl6] · 2 NC5H5. A further mol RLi effects a reduction to Li3[CeCl6] · 2 NC5H5. With an excess of RLi amidocerium(III) complexes of the typ Li4 are formed. Li2[CeCl6] is formed also at reactions of quartery ammonium salts, e. g. [C6H5CH2N(C2H5)3]2[CeCl6], with RLi (R = 1-Nor, Me22NCH2CH2CH2) followed by an reduction to Li3[CeCl6]. An excess of the lithium organyl effects the formation Li4[RCeCl6] complexes. The yielded compounds were characterized by elementary analysis, the hydrolysis and deuterolysis products, magnetic moments, and IR-spectra. 相似文献
83.
The structures of the stable conformers of N-methyjpropionamide and N-methyliso-butyroamide in CCl4, solution were determined by a combination of IR spectroscopy and NMR spectroscopy with lanthanide shift reagents. N-methyl-propionamide was found to exist in the form of two rotational isomers, 1 and 2, with the ethyl group twisted out of the plane of the amide bond by the angles Ψ = 140 and 20°, respectively. For these two conformers, the enthalpy difference is ΔH = 2.13 ± 0.08 kcal mole?1 and the entropy difference ΔS = 7.81 ± 0.55 cal mole?1 grad?1. N-methylisobutyroamide exists in a single form, with the two C-methyl group positions very close to those found in the two isomers of N-methylpropionamide. 相似文献
84.
Klapars A Waldman JH Campos KR Jensen MS McLaughlin M Chung JY Cvetovich RJ Chen CY 《The Journal of organic chemistry》2005,70(24):10186-10189
[reaction: see text] A mild and transition-metal-free method for the alpha-arylation of aliphatic nitriles with activated heteroaryl halides was developed using NaHMDS or KHMDS as base at ambient temperature. The key to the success of this method is generation of the nitrile anion in the presence of the heteroaryl halide. The method is applicable to both primary and secondary carbonitriles and a wide range of heteroaryl halides. Selective monoarylation was observed with primary carbonitriles. The operational simplicity and the mild reaction conditions add to the value of this method as a practical alternative to the preparation of alpha-heteroaryl carbonitriles. 相似文献
85.
Horváth-Szabó G Czarnecki J Masliyah JH 《Journal of colloid and interface science》2002,253(2):427-434
Equilibrium liquid crystal (LC) layer on an interface between crude oils and water was observed at high pH. This layer is composed mainly of sodium naphthenates produced in situ at the water/oil interface. Transient LC layer was also evolved at the interface of aqueous phase of sodium hydroxide solutions and oleic phase of naphthenic acid (NA) solutions as result of a chemical reaction between NaOH and NA. This chemical reaction causes transport process resulting in a disturbance of the interface. Optical observation of this interface disturbance reviled that the interface covered with LC shows considerably lower flexibility as compared to LC free interface. The LC layer eventually dissolves in the water phase at low oil-to-water ratio, while at high oil-to-water ratio it can form an equilibrium phase, which spreads spontaneously at the oil-water interface. 相似文献
86.
Pál Tapolcsányi János Wélfling Erzs?bet Mernyák Gyula Schneider 《Monatshefte für Chemie / Chemical Monthly》2004,44(3):1129-1136
The Mitsunobu inversion reaction of 3-methoxyestra-1,3,5(10)-trien-17-ol is dramatically influenced by the acidic component. There appears to be a relationship between the dissociation constant of the electron-withdrawing substituent on the aryl acid and the overall effectiveness of the reaction, with more acidic species generally providing a higher yield of inverted product. 相似文献
87.
Majumdar A Behnke JF Hippler R Matyash K Schneider R 《The journal of physical chemistry. A》2005,109(41):9371-9377
Chemical reactions in a dielectric barrier discharge at medium pressure of 250-300 mbar have been studied in CH(4)/Ar and CH(4)/N(2) gas mixtures by means of mass spectrometry. The main reaction scheme is production of H(2) by fragmentation of CH(4), but also production of higher order hydrocarbon molecules such as C(n)H(m) with n up to 9 including formation of different functional CN groups is observed. Formation of C(2)H(2), C(2)H(4), and C(2)H(6) molecules has been investigated in some detail. Significant differences are noted in comparison to a theoretical estimate. 相似文献
88.
Jacob Katriel 《International journal of quantum chemistry》1989,35(4):461-470
A combinatorial derivation of the product of the class of three cycles, [(1)N?3(3)]N with an arbitrary class operator of the symmetric group SN is presented. The form of this result suggests a conjecture concerning the expression of the general class operator product in terms of a relatively small number of reduced class coefficients. The conjecture is applied to the determination of the products of [(1)N?4(4)]N, [(1)N?4(2)2]N, and [(1)N?5(5)]N with arbitrary class operators. General expressions for the reduced class coefficients of the simplest type are obtained. 相似文献
89.
MM2 Exploration of the conformational space for methylcyclopentane, in contrast to cyclopentanone yields more and flatter minima than known previously. Calculations of cyclopentanes with substituents X = F, Cl, CHMe2, and CMe3 with two stable conformations indicate <2° torsional angle changes with the different substituents. Cyclopentanes bearing not more than 2 substituents can accommodate all groups in pseudoequatorial positions without changing the basic envelope and twist chair geometries significantly. A model for 13C-shift calculation is proposed in which shift increments for the different torsional arrangements are obtained by linear interpolation between corresponding cyclohexane values. After correction for the nonequivalent carbon shifts in the hydrocarbon itself, again using the linear interpolation, a significant improvement of the shift correlations is observed. For disubstituted cyclopentanes these predict the shifts within ± 1.7 ppm with Me, CHMe2, CMe3, Cl, Br and OH as substituents. Configurational assignments are difficult with 1,3-di-substituted cyclopentanes, but straightforward with 1,2-di- and trisubstituted compounds. Thus, due to the presence of smaller torsional angles between, e.g. diequatorial vicinal substituents in the 1,2- cis series as compared to the trans compounds, the latter show deshielding, particularly at C2, by 1–4 ppm. Several epimers are stereo-selectively prepared by suitable ketone reduction and displacement methods. 相似文献
90.
Fry FH Holme AL Giles NM Giles GI Collins C Holt K Pariagh S Gelbrich T Hursthouse MB Gutowski NJ Jacob C 《Organic & biomolecular chemistry》2005,3(14):2579-2587
Certain cancer cells proliferate under conditions of oxidative stress (OS) and might therefore be selectively targeted by redox catalysts. Among these catalysts, compounds containing a chalcogen and a quinone redox centre are particularly well suited to respond to the presence of OS. These catalysts combine the specific electrochemical features of quinones and chalcogens. They exhibit high selectivity and efficiency against oxidatively stressed rat PC12, human Jurkat and human Daudi cells in cell culture, where their mode of action most likely involves the catalytic activation of existent and the generation of new reactive oxygen species. The high efficiency and selectivity shown by these catalysts makes them interesting for the development of anti-cancer drugs. 相似文献