Development of Yttrium and Iron Oxide Thin Films via AACVD Method for Photooxidation of Water

Russian Journal of Applied Chemistry - Owing to high stability, metal oxide-based ceramic thin films are of great interest for photocatalytic oxidation of water. Therefore, the current research is...     

A Validated LC Method for the Quantitation of Cefotaxime in pH-Sensitive Nanoparticles

A sensitive and rapid routine LC method was validated for measuring cefotaxime incorporated in three different pH-sensitive nanoparticles. The drug was chromatographed on a C18 reversed-phase column; the mobile phase used was 0.05 M aqueous ammonium acetate, acetonitrile and tetrahydrofuran (87:11:2, v/v) adjusted to pH 5.5 with acetic acid. The flow rate was 1 mL min^?1 and cefotaxime was quantified at 254 nm, with a sensitivity range of 0.005 AUFS. The validated method was specific, linear (R ² ≥ 0.999), precise and accurate in a concentration range of 0.2–50.0 μg mL^?1. The method was rapid, selective and suitable for evaluation of cefotaxime in pH-sensitive Eudragit nanoparticles.     

Methyl Methacrylate–Ethyleneglycol Dimethacrylate–Acrylic Acid Surface as Stationary Phase for Stir Bar Sorptive Extraction

A novel poly(methyl methacrylate–ethyleneglycol dimethacrylate–acrylic acid) film has been introduced for coating on stir bars to sorptive extraction (SBSE). The effects of different contents of porogen, monomer, cross-linker, modifier and initiator during the solvent or bulk polymerization step on the mechanical property and solvent resistant of prepared sorptive stir bars were investigated. The evaluation of results were caused to obtain the four prepared sorptive stir bars with good mechanical stability and excellent resistance to organic solvents. The extraction efficiency of these prepared sorptive stir bars were investigated by liquid desorption-liquid chromatography-ultraviolet detection (LD-LC-UV) using N-Nitrosodiphenylamine as target analyte. SBSE assays showed the sorptive stir bar that prepared using solution polymerization method had the better recovery for N-Nitrosodiphenylamine in water samples. This sorptive stir bar showed good linearity and acceptable recoveries, as well as advantages such as sensitivity, simplicity, low cost and high feasibility. Based on atomic force microscopy (AFM) results, the average pore size of optimum prepared stir bar using solvent polymerization method was obtained ~9 nm. The thermal gravity (TG) and differential scanning calorimetric (DSC) results showed this polyacrylate film has high thermal stability.     

Solid state NMR spectroscopy as a precise tool for assigning the tautomeric form and proton position in the intramolecular bridges of o-hydroxy Schiff bases

Two analogous Schiff bases, (S,E)-2-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylimino)methyl)phenol (1) and (S,Z)-2-hydroxy-6-((1-hydroxy-3-methyl-1,1-diphenylbutan-2-ylamino)methylene)cyclohexa-2,4-dienone (2), exist in the solid state as phenol-imine and keto-amine tautomers, respectively. Their crystal structures were solved using the X-ray diffraction method. Sample 1 forms orthorhombic crystals of space group P2(1)2(1)2(1), while 2 forms monoclinic crystals of space group P2(1). In each sample, one molecule is in the asymmetric unit of the crystal structure. One-dimensional and two-dimensional solid state NMR techniques were used for structure assignment and for inspection of the (13)C and (15)N δ(ii) of the chemical shift tensor (CST) values. NMR study indicates that the span (Ω = δ(11)-δ(33)) and the skew (κ = 3(δ(22)-δ(iso)/Ω) are extremely sensitive to change in the tautomeric form of the Schiff bases. Theoretical calculations of NMR shielding parameters for 1 and 2 and a model compound with reduced aliphatic residue were performed using the GIAO method with B3LYP functional and 6-311++g(d,p) basis sets. From comparative analysis of the experimental and theoretical parameters, it was concluded that the position of hydrogen in the intramolecular bridge has tremendous influence on (13)C and (15)N CST parameters. Inspection of Ω and κ parameters allowed for the establishment of the nature of the hydrogen bonding and the assignment of the equilibrium proton position in the intramolecular bridges in the solid state.     

Solvent effect on the kinetics and mechanism of the thermal decomposition oftris-oxalactocobaltate(III) complex

Summary The kinetics of the thermal decomposition of thetris-oxalactocobaltate(III) complex has been investigated in the presence of EtOH and (CH₂OH)₂ spectrophotometrically in the 50–70 ± 0.1 ° C range. The rate of the reaction decreases upon the addition of either of the alcohols to the reaction medium, whereas the activation energy increases. The thermodynamic parameters were calculated and are discussed in terms of the solvation effects. The influence of the dielectric constants of the solvent mixtures on the rate has been studied. A free radical mechanism is proposed and discussed.     

Barrier to internal rotation in 2,3- and 3,3-difluoropropenal and their methyl derivatives

The conformational stability and structure of 2,3-dimethylpropenal, 2,3-difluoropropenal and their 3,3-dimethyl and 3,3-difluoro derivatives were investigated utilizing ab initio calculations with 3-21G and 6-31G basis sets. For 2,3-dimethylpropenal and 3,3-difluoropropenal the s-trans was predicted to be the low-energy form. In the case of 3,3-dimethylpropenal and 2,3-difluoropropenal the s-cis was predicted by both levels of calculation to be the more stable conformer. Full optimization was performed at the transition states and the barriers to internal rotation were calculated. Methyl and fluorine substitution were found to significantly increase the barrier to interconversion in propenal. The relative change in the barrier depends on the position and the type of the substituent. The trans to cis barrier in 2,3-dimethylpropenal was calculated to be about 3 kcal mol⁻¹ greater than that in 3,3-dimethylpropenal, while the cis to trans barrier in 2,3-difluoropropenal was predicted to be about 7 kcal mol⁻¹ higher than the corresponding one in 3-3-difluoropropenal.     

Spectrophotometric study of vanadium(V)-phenylfluorone complex

Spectrophotometric studies of the reaction between vanadium(V) ions and phenylfluorone are presented and used for spectrophotometric determination of vanadium(V). The absorbance at 520 nm obeys Beer's law in the range of 2–15 μg vanadium/10 ml at pH 4. The relative standard deviation is 2% and the molar absorptivity based on vanadium is 2.1 × 10⁴ liters/mol cm. The composition of the complex in solution is of the 1:1 type with stability constant values to 2.5 × 10⁴. Analysis of the solid complex shows that its formula agrees with the formula (C₁₉ H₁₁ O₅)VO₂ · 5H₂O.