Simple, expedient methods for the determination of water and electrolyte contents of cellulose solvent systems

The concentrations of water, W, and electrolytes present in solutions of LiCl in N,N-dimethylacetamide, LiCl/DMAc, and of tetrabutylammonium fluoride. x-hydrate in DMSO, TBAF.xW/DMSO can be accurately and expediently determined by three independent methods, UV–vis, FTIR and EMF measurement. The first relies on the use of solvatochromic probes whose spectra are sensitive to solution composition. It is applicable to W/LiCl/DMAc solutions but not to TBAF.xW/DMSO, because the charge-transfer complex bands of the probes are suppressed by strong interactions with the latter electrolyte. Integration of ν_OH band of water may be employed in order to determine [W], hence [electrolyte] by weight difference. EMF measurement uses ion-selective electrodes in order to determine [electrolyte], hence [W] by weight difference. Results of the latter method were in excellent agreement with those of FTIR. The reason for the failure of Karl Fischer titration is addressed, and the relevance of the results obtained to functionalization of cellulose under homogenous solution conditions is briefly commented on.     

Novel approach to arylhydrazones, the precursor for Fischer indole synthesis, via diazo esters derived from α-amino acid esters

A novel method for synthesizing arylhydrazones, the precursor for Fischer indole synthesis, using aryllithium reagents and α-diazo esters that are easily obtained from α-amino acid esters, is described.     

A new scheme for the mechanism of Fischer indolization of arylhydrazones

A new scheme for the mechanism of Fischer indolization of arylhydrazones has been suggested based on quantum-chemical calculations by the MNDO AM1 method.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 961–962, May, 1994.     

Synthesis of thieno[3.2-<Emphasis Type="Italic">b</Emphasis>]pyrrolenine derivatives under the Fischer reaction conditions

The reaction of alkyl 4-(2-acetylhydrazino)-2-methyl-3-thiophenecarboxylates with 3-methylbutan-2-one was carried out under the Fischer reaction conditions. The influence of Lewis acids and solvents on the process was studied. A convenient method for the synthesis of thieno [3.2-b]pyrrolenine derivatives was proposed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 725–729, March, 2005.     

An automated FTIR method for the routine quantitative determination of moisture in lubricants: An alternative to Karl Fischer titration

An accurate primary Fourier transform infrared (FTIR) method for the determination of moisture in mineral and ester based lubricants has been developed based on the extraction of moisture into dry acetonitrile. FTIR evaluation of acetonitrile extracts from new and used lubricants as well as common lubricant additives and contaminants which might co-extract indicated that phenolic constituents interfered significantly with moisture measurements. By measuring moisture at 3676 cm⁻¹ on the shoulder of the asymmetric OH stretching band, spectral interferences from extracted phenolic constituents were minimized. The spectra of calibration standards (0-2100 ppm), prepared by gravimetric addition of water to dry acetonitrile, were recorded in a 1000-μm CaF₂ transmission flow cell and produced linear standard curves having an S.D. of ∼±20 ppm. Lubricant sample preparation involved the vigorous shaking (20 min) of a 1:1.5 (w/v) mixture of lubricant and dry acetonitrile, centrifugation to separate the phases, acquisition of the FTIR spectrum of the upper acetonitrile layer, and subtraction of the spectrum of the dry acetonitrile used for extraction. A Continuous Oil Analyzer and Treatment (COAT^®) FTIR system was programmed to allow the automated analysis of acetonitrile extracts, and the methodology was validated by analyzing 58 new and used oils, independently analyzed by the Karl Fischer (KF) method. Linear regression of FTIR versus KF results for these oils produced a linear plot with a between-method S.D. of ±80 ppm. As implemented on the COAT^® system, this FTIR method is capable of analyzing 72 acetonitrile extracts/h and provides a high-speed alternative to the KF titrimetric procedures for the determination of water in lubricants.     

A facile synthesis of 4- and 6-chloromethyl-1H-indole-2-carboxylates: replacement of a sulfonic acid functionality by chlorine

Valuable new synthetic intermediates, 4- or 6-chloromethyl-1H-indole-2-carboxylates, were prepared by the elimination of SO₂ from 2-ethoxycarbonyl-1H-indole-4- or 6-methanesulfonic acids, respectively, which are easily accessible by Fischer-type indolization.     

Transition metal carbene chemistry 2: kinetic studies on the nucleophilic substitution reactions of (CO)5MC(SCH3)CH3 (M = Cr and W) with morpholine in aqueous acetonitrile

Kinetic studies of the aminolysis of [methyl(thiomethyl)carbene]pentacarbonyl chromium(0),(CO)₅CrC(CH₃)(SCH₃) (1-Cr(S)) and [methyl(thiomethyl)carbene]pentacarbonyltungsten(0), (CO)₅WC(CH₃)(SCH₃) (1-W(S)), with morpholine, a secondary amine, in 50% acetonitrile-50% H₂O (v/v at 25 °C) is reported. The second-order rate constant (k_A in m⁻¹ s⁻¹) increases with amine concentration, giving a linear dependence with an intercept on the rate axis and a tendency towards leveling off at higher amine concentration. The reaction was found to undergo general base catalysis. The mechanism proposed is very similar to those for ester reactions, involving a nucleophilic addition of amine to the substrate to yield a zwitterionic tetrahedral intermediate in the first step, followed by deprotonation to form in the second step, which, in the third step, converted to product by H₂O and/or conjugate acid of the base (BH⁺), assisted MeS⁻ expulsion. The reactivity (k₁) of 1-W(S) was found to be higher than that of 1-Cr(S), whereas, comparable , water catalyzed and , BH⁺ catalyzed, leaving group departure were found for both the carbenes complexes. All these observations have been explained successfully.     

Synthesis of Nonracemic 9-(1-Methoxycarbonylethyl)-1,2,3,4-tetrahydrocarbazole

A new approach has been proposed to the synthesis of indole derivatives containing a chiral substituent at the nitrogen atom, comprizing Fischer indolization of phenylhydrazines with a chiral substituent at the -nitrogen atom. The initial hydrazines were obtained by the alkylation (Mitsunobu reaction applying optically active esters of lactic acid) of anilines containing an electron-accepting substituent at the amino group. Subsequent removal of the activating acceptor grouping was realized by nitrosation of the chiral secondary aniline followed by reduction of the corresponding N-nitroso compound.     

合成气制低碳烯烃用Fe／AC催化剂的制备及性能表征

 研究了以活性炭（AC）作为载体制备的铁基催化剂，通过对不同铁盐、活性炭和助剂的筛选，研制出对合成气转化为低碳烯烃具有高活性和高选择性的催化剂．对反应前及反应过程中催化剂体相结构的XRD测试结果表明，Fe－Cu－K／AC催化剂在反应前主要由α－Fe，Fe3O4和Cu0组成，经合成气反应后主要由α－Fe，Fe5C2，Fe7C3，Cu0和K2O组成．Fe－Mn－K／AC催化剂的晶体结构主要以Fe嵌入MnO中形成的（Fe，Mn）O结构存在．实验中得出的α－Fe，FexCy及（Fe，Mn）O与激光热解法制备的催化剂的的晶体结构相似．对催化剂的制备方法进行了筛选，考察了不同助剂Cu，Mn，Si和K等元素对催化剂性能的影响．结果表明，以草酸铁为铁源，椰壳炭为载体制备的Fe－Mn－K／AC催化剂的催化效果最佳，在空速600h－1，压力1．5MPa和温度320℃条件下，CO转化率可达97．4％，C＝2～C＝4选择性可达68．0％．     

Organometallic Aspects of the Fischer-Tropsch Synthesis

The Fischer-Tropsch Synthesis counts among the industrial-scale processes having a versatile and broad product range, and has for decades offered the most attractive possibility for the use of coal as a source of heating oil and fuels. This conceivably simple reaction, the catalytic hydrogenation of carbon monoxide, generally leads to simple hydrocarbons as well (i.e. short chain olefins) that have been sought as chemical feedstocks since the oil crisis of the seventies, but fails to provide the large-scale, economic process required, due in large part to the minimal selectivity of traditional Fischer-Tropsch processes. In an effort to solve this problem current research in this sector is concerned not only with the optimization of old and the development of new catalytic systems, but also increasingly with the elucidation of numerous relevant reaction mechanisms. This article will discuss, from the viewpoint of an organometallic chemist, the significance of typical model reactions, both with regard to some fundamental aspects of synthesis gas chemistry, and in comparison with previous views concerning the mechanism of the Fischer-Tropsch Synthesis. The importance of various unique classes of complexes that have been studied in the context of Fischer-Tropsch chemistry is also evaluated with regard to their importance in the synthesis of hydrocarbons from carbon monoxide and hydrogen. It emerges that the primary steps of the reductive oligomerization of carbon monoxide are best described by the carbide/methylene mechanism, as originally proposed by Hans Fischer and Franz Tropsch.