Spontaneous assembly of organic thiocyanates on gold sufaces. Alternative precursors for gold thiolate assemblies

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.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 47. Zur Reaktion von Hexachloroceraten(IV) mit Lithiumorganylen

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.     

Mild and practical method for the alpha-arylation of nitriles with heteroaryl halides

[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.     

Sandwich structures at oil-water interfaces under alkaline conditions

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.     

Products of class operators of the symmetric group

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 S_N 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.     

Multifunctional redox catalysts as selective enhancers of oxidative stress

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.     

Sensing the physicochemical nature of he and ne in micropores by adsorption measurements

He and Ne in contact with molecular sieves in the form of crystalline A zeolites and amorphous carbon molecular sieves fibers (CMSF) were studied by adsorption measurements. Classification of the effective enclosure of zeolitic apertures and of graphitic constrictions, as determined by recent temperature-programmed desorption mass spectrometry (TPD-MS) studies of adsorption of He and Ne onto these materials, was utilized in making a prudent choice of samples and experimental conditions. In view of the former TPD information, the behaviors of adsorption and volumetric measurements reported herein are straightforwardly interpreted. The combined TPD, adsorption isotherms, and dead volume data deepen the understanding of the physicochemical nature of adsorbed gas, where gas adsorption in the vicinity of pore constrictions and/or apertures as well as on the inner surface areas of pores and/or cages could be resolved. Previous conclusions that the huge activation energies measured for Ne/CMSF at high temperatures are unlikely to characterize chemical desorption but reflect those required for overcoming the barrier of effectively constricted apertures were confirmed by the volumetric data presented here. At 77 K, considerable He adsorption was observed in the porous solids and found to be responsible for abnormal deduced values of dead volumes. The occurrence of significant adsorption of He onto A zeolites and CMSF at 77 K warrants the realization that in cases concerning porous materials, volumetrically deduced quantities should not be taken for granted, but should be carefully considered and uniquely interpreted in relation to the specific experimental conditions under which they are taken.     

Gas chromatographic analysis of bifunctional amines after derivatization with methyldichlorophosphine and sulfur

Summary A derivatization procedure for the gas chromatographic analysis of bifunctional amines likeβ-adrenergic blocking drugs is described. The method consists of a two-step reaction with methyldichlorophosphine and sulfur in presence of triethylamine to form cyclic methylphosphonothioic derivatives. The properties of these compounds are discussed and the application of the method to the quantitation of ephedrine in human body fluids is presented. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Hydroselenation of alkynes using NaBH4/BMIMBF4: easy access to vinyl selenides

A general and easy method for the synthesis of several vinyl selenides using NaBH₄ and BMIMBF₄ as a recyclable solvent is described. This efficient and improved method furnishes the corresponding vinyl chalcogenides preferentially with Z configuration. We also observed that when the same protocol was applied to phenyl acetylene, (E)-bis-phenylseleno styrene was obtained in good yield and with high selectivity.     

Germanium-oxygen interactions in acyl-substituted germyleneazines L2GeNNC(COX)(COY)

MNDO calculations have been carried out on the reactions of the electron-rich germylene L₂Ge [L=(H₃Si)₂N] with diazo compounds, as models for the experimentally observed reactions of L₂Ge [L=(Me₃Si)₂N]. The most stable form of the 11 adduct of L₂Ge with N₂C(COOMe)₂ is found to have a cyclic configuration resulting from a strong intramolecular interaction between the oxygen of one of the carbonyl groups and the germanium atom. Protonation of this cyclic adduct occurs at nitrogen, giving an intermediate, addition to which of nucleophiles X^– provides acyclic L₂Ge(X)NHN(COOMe)₂, as observed experimentally. Two similar cyclic adducts are formed between L₂Ge and N₂C(COCH₃)(COOCH₃), the most stable of which provides, after a proton shift, the observed 1,3,4,2-oxadiazagermine system . Adduct formation between Me₂Si=NSiMe₃ and simple Lewis bases (H₂O, NH₃, THF, H₂CO) is calculated to be strong, but the corresponding adducts of Me₂Ge=NSiMe₃ are very weak: much stronger adducts are predicted for L₂GeNNC(COOMe)₂.