An Efficient Procedure for Esterification of Aryloxyacetic Acid and Arylthioacetic Acid Catalyzed by Silica Sulfuric Acid

Aryloxyacetate and arylthioacetate are wildly used in herbicides, plant regulator and insecticides. Recently, Wille et al. have reported that methyl aryloxyacetate is an efficient agent to prevent and treat allergic contact dermatitis.[1] The most popular synthesis is by heating sodium phenoxide (mercaptide) with ethyl chloroacetate in DMF,[2] or by the esterification of acid with alcohol using concentrated H2SO4 as catalyst.[3] In this paper, synthesis of aryloxyacetate and aryl thioacetate from aryloxyacetic acid and arylthioacetic acid respectively in ether catalyzed by silica sulfuric acid in 83%～94% yields is described. The catalyst is reused for 3 times without significant loss of activity (Entry 4). Compared with common procedures, the present procedure possesses the advantages of the operational simplicity, short reaction time,less-corrosion, high yield and reusable catalyst.     

Direct Polymerization of Polyacrylic Acid on Mica Substrates using ATRP – A Preliminary Study

Summary: Unprecedented direct polymerization of sodium acrylate (NaA) on mica and silica substrates was undertaken using standard ATRP polymerization conditions at room temperature. The resulting thickness of the poly(sodium acrylate) (PNaA) grafted layer was determined using ellipsometry and AFM.     

Effect of Synthesis Parameters on Sol–Gel Silica Modified by Zirconia

An experimental strategy was developed to obtain mesoporous SiO₂-ZrO₂ mixed oxides via a sol–gel process, which involved the use of tetraethylorthosilicate (TEOS) and an inorganic Zr-containing salt. The effects of key process parameters on the properties of the materials were investigated, including the choice of Zr(IV) source (zirconium oxychloride or nitrate), the ZrO₂ content and the synthesis pressure (i.e. ambient pressure or hydrothermal conditions). The resulting solids were dried, calcined at 500 °C, and characterized by nitrogen physisorption, pyridine chemisorption, ²⁹Si Nuclear Magnetic Resonance and X-ray diffraction. The data revealed that mesoporous materials with very narrow pore diameter distribution were obtained when using the autoclave procedure from both zirconium nitrate and oxychloride salts. The surface areas and pore size distributions were a function of ZrO₂ content. Differences in acidity, as determined by pyridine adsorption, were observed depending on the synthesis parameters.     

Letter to the Editor: Friction between Surfaces—Polyacrylic Acid Brush and Silica—Mediated by Calcium Ions

With this letter, we report how friction can be controlled by inducing physical bonds solely within a polyelectrolyte brush layer, while keeping repulsive interactions between the brush layer and the bare surface that slides above. Our results imply that the nature of the bare surface is of minor importance as long as the repulsive surface interaction is maintained.     

Tartaric Acid Modified Electrodes and Studies on its Application for the Anodic striphing Voltammetry of cu(Ⅱ)

The preparation of tartaric acid modified electrode was studied.Reaction mechanism of copper(Ⅱ) on tartaric acid modified electrode was discussed and determination conditions for trace Cu(Ⅱ) by ASV were also founded.     

Catalytic Cleavage of Phosphate by Modified Polyethylenimines (Ⅱ)

A series of modified polyethylenimines (PEIs) containing oxime groups and cetyl groups were prepared. The dissociated constants of oxime group and the rate constants of its reaction with p-nitrophenyl diphenyl phosphate (PNPDPP) were determined. These polymers are good catalysts for the cleavage of PNPDPP under aqueous conditions. Rate accelerations approach 10~4-10~5-fold level with turnover behavior. Reaction mechanism is analogous to that of enzyme-catalyzed kinetics.     

A Novel Method for Beckmann Rearrangement of Oximes with Silica Sulfuric Acid under Mild Condition

The conversion of ketoxime into corresponding amide, known as the Beckmann rearrangement, is a common method used in organic chemistry and is also a topic of current interest. It accomplishes both the cleavage of carbon-carbon bond and the formation of a carbon-nitrogen bond, and represents a powerful method particularly for manufacture ε-caprolactam in chemical industry. This reaction, however, generally requires high reaction temperature, strong Br?nsted acid and dehydrating media, causing …     

Determination of Lewis Acid Base Properties of Poly(??-n-alkyl) Methacrylates Adsorbed on Silica by Inverse GC

In this paper, the acid base properties in the Lewis terms of poly(??-n-alkyl) methacrylates and when they are adsorbed on silica, were determined. The acid base constants K _A and K _D of various polymers were calculated by testing the classical model and proposed a new model giving K _A and K _D and a third constant K reflecting the amphoteric character of our solid substrates and obtaining more precise and quantified results. When the length of alkyl group in side chain of poly(??-n-alkyl) methacrylates changes, the surface properties of such polymers also change and consequently affect all superficial characteristics and especially the acid base constants and the transition phenomena. It was also proved that the specific enthalpy was directly correlated to the acid base constants, the carbon atom number in the side chain of poly(??-n-alkyl) methacrylates and the acceptor AN and donor DN numbers of electrons of polar organic molecules, by the following relationship: ??H ^sp?=???H ^sp(AN, DN, K _D, K _A, n _SC).     

Numerical Method for Determination of Composition of Weak Acid Mixtures by Potentiometric Titration

An equation describing the state of weak acid mixtures was derived from the relationships between mole balance and charge balance. The equation was solved with numerical method and the compositions of the acid mixtures were determined. The advantages of this treatment were demonstrated by analyzing binary mixtures of chloroacetic, formic and acetic acids.     

studies on the Mechanism of Producing Tungstic Acid by Complex-Homogeneous Precipitation Method

A new method of producing tungstic acid with a yield over 98% at room temperature and low acidity is advanced and referred to as Complcx -Homogeneous Precipitation Method. If combined with the treatment of activated charcoal in recovering the remnant tungsten left in the filter liquor, a perfect closed technological process can be obtained. The key to this method is to prevent the formation of pseudo-metatungstatc during scdium rungstate being acidified directly with the aid of the complexing-protecting agent H2O2, The perexo-mtermediate, which was prepated and identified as dipcroxytetratnngstate by IR and Raman analysis by comparison with diperorytetramolybdate, can be decomposed by SO2 tapidly and quantitatively. The tungstic acid precipitate can be filtered and washed easily. The related mechanisin is studied.     

A Modified Method for Synthesis of Alkyl Hydrogen α-(Benzyloxycarbonylamino)-benzylphosphonates

A series of alkyl hydrogen α-(benzyloxycarbonylamino)benzylphosphonates are prepared from benzyl carbamate, substituted benzaldehydes and alkoxydichlorophosphine in acetyl chloride and subsequent hydrolysis. Compared with the previous methods, the reaction avoids producing the corresponding diesters and thus improves the yields of the products.     

Investigation and Application of Polarographic Catalytic Wave of Oxygen Reduction Caused by Mefenamic Acid

The polarographic catalytic wave of oxygen reduction caused by mefenamic acid (MA) with redox properties was reported in this paper. The electrochemical process of the catalytic wave was proposed that the superoxide anion O(?) was generated polarographically and the dismutation of the O(?) was catalyzed by MA to reproduce O_2 and H_2O_2. This explained chemically the scavenging of the O_2~- by MA im biomedical area. Based on the catalytic wave, a new method for the determination of MA by single-sweep polarography was developed.     

Efficient Method for Synthesis of the Derivatives of 5‐Arylidene Barbituric Acid Catalyzed by Aminosulfonic Acid With Grinding

Aminosulfonic acid is an environmentally friendly catalyst. Grinding a mixture of aromatic aldehydes, barbituric acid, and H₂NSO₃H at room temperature (without any solvent) gave 5‐arylidene barbituric acid in high yields, providing a simple and efficient route to synthesis of these compounds.     

Determination of Ferulic Acid in Rat Plasma by Liquid Chromatography–Tandem Mass Spectrometry Method: Application to a Pharmacokinetic Study

Abstract

A rapid, sensitive, and specific liquid chromatography–tandem mass spectrometric (HPLC-MS/MS) method has been developed for quantification of ferulic acid in rat plasma. The analyte and docetaxel (internal standard) were extracted from plasma samples with diethyl ether and analyzed on a C₁₈ column. The chromatographic separation was achieved within 3.5 min by using acetonitrile-water as the mobile phase and the flow rate was 0.2 mL · min^?1. The method was linear within the range of 0.5 ? 800 ng · mL^?1. The lower limit of quantification (LLOQ) was 0.5 ng · mL^?1. Finally, the method is successfully applied for the pharmacokinetic study of ferulic acid in rats following intravenous administration.     

In-Situ Synthesis of Terbium Complex with Salicylic Acid in Silica Matrix by a Two-Step Sol-Gel Process

Sincesomelanthanideionspossessgoodlundnescentcharacteristicsbasedontheelectronictransitionsbetweenthe4fenergylevels,aseriesofrareearthcompoundshavebeenstudiedforpracticalapplicationsasphosphors.However,sincethef-ftransitionsoftheseionsareparityforbidden,theintensityofabsorptionbandsareusuallyrelativelyweak.Itiswellknownthatorganicligandsusuallyhavehighultravioletmolarabsorptivity.Ifthecomplexesthatcontainthiskindofligandsaresynthesized,theywillgivestrongluminescence.Infact,sofarmanyphotoactive…     

Liquid Chromatographic Resolution of Enantiomers on Chiral Amide Bonded-Silica Gel Normal Phase Separation of Racemic α-Amino Acid Derivatives by N-Acetyl-L-valyl-aminopropyl-silanized Silica (AVA) Phase

Abstract

A new optically active stationary phase obtained by grafting N-acetyl-L-valine with 3-aminopropylsilanized silica was developed. The high-efficiency chiral column was prepared by slurry packing procedure. Direct resolution of the racemates of α-amino acid derivatives was accomplished by using normal phase liquid chromatography.     

Preparation and Application of La(OH)3 Nanoparticles Self‐Assembled Film Modified Electrode

Abstract

La(OH)₃ nanoparticles were successfully prepared with the sol‐gel method, and the preparation of a glassy carbon electrode modified by La(OH)₃ nanoparticles was investigated. The modified electrode shows an excellent electrocatalytic activity for hydroquinone. The anodic and cathodic overpotentials are reduced by ca. 143 mV and 83 mV, respectively, compared with those obtained with a bare glassy carbon electrode. According to the electrochemistry response, we set up a new method to determinate hydroquinone. The catalytic anodic current response of differential pulse voltammogram increases linearly with hydroquinone concentrations from 2.7×10^?7 to 6.5×10^?4 mol L^?1 with a detection limit of 6.0×10^?8 mol L^?1. The recovery of hydroquinone in a simulative sample is satisfactory, especially for its elimination of the interference of 1,2‐benzenediol (pyrocatechol) and 1,3‐benzenediol (m‐dihydroxybenzene). The method is simple, quick, and sensitive.     

Discrimination of Tea by the Electrochemical Determination of its Antioxidant Properties by a Polyaniline – DNA – Polyphenazine Dye Modified Glassy Carbon Electrode

Abstract

Voltammetric sensors have been developed on the bases of polyaniline and polymeric forms of methylene blue, methylene green, and neutral red obtained by multiple cycling of the potential. The integrity of the layers and expansion of the pH range of redox activity have been achieved by intermediate adsorption of native DNA that stabilized the oxidized polyaniline form. The formation of the coating layer was confirmed by electrochemical impedance spectroscopy and scanning electron microscopy. Model oxidants (ascorbic acid, hydroquinone, and quercetin) in the concentration range from 1?×?10^?6 to 1?×?10^?3 mol L^?1 influenced the measured redox peaks of polymeric dyes with standard deviations from 2.4 to 5.5%. The peak currents were used for classification of tea brands using principal component analysis and linear discrimination analysis. The average discrimination of the tea brands purchased on local market was approximately 100%. The assessment of antioxidant properties of tea infusions was in agreement with results obtained using a coulometric bromine titration.