Oxidative dihydroxylation of alicyclic unsaturated hydrocarbons with vinyl- and norbornene fragments in pseudohomogenic system

Oxidation of alicyclic unsaturated hydrocarbons (4-vinylcyclohexene, 5-vinylnorbornene, 5-cyclohexenylnorbornene, and 5-vinylbicyclooctene) with 30% hydrogen peroxide solutions and percarbamide is studied. Reaction was carried out at 40–70°C in the presence of heterogenized peroxocomplex compounds of molybdenum and tungsten formed “in situ” in the reaction of metal oxohalides with H₃PO₄, nano-dimensional particles of carbon material, and hydrogen peroxide. Main oxidation products of alicyclic diene hydro-carbons are the corresponding unsaturated epoxides and diols. Depending on the reaction condition their ratio varies in a wide range.     

Tautomeric composition and tautomeric transformation sequence of 1,4-bis(alkylamino)anthraquinones

Compounds widely known as 1,4-bis(alkylamino)-9,10-anthraquinones are in fact neither individual substances nor substituted 9,10-anthraquinones but equilibrium mixtures of tautomers. Their aminoimine tautomeric transformations follow the sequence 4,9-bis(alkylamino)-1,10-anthraquinones ? 9-alkylamino-4-(alkylimino)-10-hydroxy-1,4-dihydroanthracen-1-ones ? N ¹,N ¹⁰-dialkyl-4,9-dihydroxy-1,10-dihydroanthracene-1,10-diimines.     

Quantum-chemical study on reactions of isocyanates with linear methanol associates: VIII. Relative reactivity of linear phenol and methanol associates toward methyl isocyanate

The mechanisms of the reactions of methyl isocyanate with phenol monomer and linear dimer were studied at the B3LYP/6-311++G(df,p) level of theory, and the results were compared with those obtained for the reactions with methanol associates. All the examined reactions involve asymmetric concerted transition states. The addition of phenol is electrophilic, whereas the addition of methanol is nucleophilic. The formation of H-complexes with phenol and methanol molecules increases not only electron-donating power but also gasphase acidity and basicity.     

Quantum-chemical study on thermal transformations of urea in ethylene glycol

Thermal decomposition of urea in ethylene glycol with formation of isocyanic acid and ammonia was studied at the B3LYP/6-311++G(df,p) level of theory. The decomposition process is efficiently catalyzed by monomeric and dimeric forms of ethylene glycol. Ethylene glycol dimer formed via intermolecular hydrogen bonding is a stronger acid than the monomeric species, which is responsible for the higher catalytic activity of the former. Ethylene glycol associates efficiently catalyze addition of ammonium to isocyanic acid in the synthesis of ethylene carbonate.     

Synthesis of reduced graphene oxide and its electrocatalytic properties

The method of the chemical synthesis of reduced graphene oxide was developed. Sodium hypophosphite and sulfi te were used as reducing agents. The formation of reduced graphene oxide was confi rmed by several methods. Volt-ampere characteristics of electrodes based on reduced graphene oxide were investigated in an experimental model of an oxygen fuel cell with an alkaline electrolyte. Characteristics of oxygen electrodes based on reduced graphene oxide were stable over semiannual tests. The resulting reduced graphene oxide is a promising material for oxygen electrodes of chemical current sources.     

Calorimetric study of poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K

For the first time, the heat capacity $ C_{\text{p}}^{^\circ } $ of poly(2-ethylhexyl acrylate) has been studied in an adiabatic vacuum calorimeter between 7 and 350 K, the standard thermodynamic functions: heat capacity $ C_{\text{p}}^{^\circ } $ (T), enthalpy H°(T) ? H°(0), entropy S°(T) ? S°(0), Gibbs function G°(T) ? H°(0) have been calculated from T → 0 to 350 K. The energy of combustion Δ_c U of the compound under study has been measured in a calorimeter with a stationary bomb and an isothermal shell. The standard enthalpy of combustion Δ_c H° and thermodynamic parameters of formation—enthalpy Δ_f H°, entropy Δ_f S°, Gibbs function Δ_f G°—at T = 298.15 K have been calculated. The results have been used to calculate the thermodynamic characteristics of 2-ethylhexyl acrylate bulk polymerization into poly(2-ethylhexyl acrylate) over the range from T → 0 to 350 K.     

高效液相色谱-质谱联用法测定烟草中茉莉酸

采用高效液相色谱-质谱(HPLC-MS)联用法检测烟草中茉莉酸(JA)含量。样品研磨均质后经丙酮和柠檬酸萃取,离心分离,取上清液,氮气吹去丙酮后用乙醚萃取。经氨丙基固相萃取柱净化,吹干后用色谱流动相溶解,过0.45μm有机滤膜。利用高效液相色谱-质谱联用电喷雾负离子,选择离子监测模式进行检测,内标法定量。结果表明,待测样品JA浓度范围在5～1 000ng/mL之间,标准曲线具有良好的线性关系。方法检出限(S/N≥3)是2.0ng/mL。平均回收率为80.6%～101.1%,相对标准偏差为3.5%～14.6%。应用该方法检测烟草打顶与不打顶植株之间JA含量的差异,结果比较理想。     

NMR, DTA, and impedance spectroscopy studies of ion mobility, phase transitions, and ionic conductivity in K1 − x (NH4) x SbF4 crystals

The ion mobility, phase transitions, and ionic conductivity in the crystal phases in the KF-NH₄F-SbF₃ system were studied by NMR, DTA, and impedance spectroscopy. An analysis of the ¹⁹F and ¹H NMR spectra showed how the character of ionic motions in the fluoride and proton sublattices changed with temperature. The types and temperature ranges of ionic motions were determined. Diffusion of the fluoride and partially ammonium ions was found to be the dominant form of ionic motion in the high-temperature modifications formed as a result of phase transitions. According to the electrophysical data, the high-temperature K_{1 ? x} (NH₄) _x SbF₄ phases (0.05 ≤ x ≤ 0.75) are superionic, their conductivity reaching ～10^?2–10^?3 S/cm at 450–500 K.     

Facile Fabrication of Zirconia Modified Screen‐Printed Carbon Electrodes for Electrochemical Sensing of Phosphate

We report here a facile method to immobilize zirconia nanoparticles on a disposable screen‐printed carbon electrode (designated as ZrO₂‐SPCE) for phosphate sensor application. Simply by ultrasonicating a bare SPCE in a ZrO₂ slurry, ZrO₂ nanoparticles can be immobilized effectively on the electrode surface as verified by surface characterization evidences. Using ferricyanide as a redox probe, an increase in the charge transfer resistance (R_ct) of ferricyanide upon adsorption of phosphate on ZrO₂ is used for the determination of phosphate. This ZrO₂‐SPCE phosphate sensor shows a wide linear range up to 1 mM and a detection limit of 1.69 µM (S/N=3). Practical applicability of the ZrO₂‐SPCE is demonstrated by detecting phosphate content in human blood samples.