Acid-Base Equilibrium of 5-Methoxy-6-methyluracil in Solutions: Evaluation of Content of Anionic Forms in Aqueous Alkaline Solution

Dissociation constants of 5-methoxy-6-methyluracil, 5-methoxy-1,6-dimethyluracil and 5-methoxy-3,6-dimethyluracil in water are determined. Basing on the obtained рK_а1 values, the content of anions in aqueous alkaline solution of 5-methoxy-6-methyluracil was calculated. The results were confirmed by the use of model compounds: 5-methoxy-1,6-dimethyluracil and 5-methoxy-3,6-dimethyluracil using the NMR spectroscopy.     

5-Hydroxy-6-methyluracil as an efficient scavenger of peroxy radicals

The reaction of 5-hydroxy-6-methyluracil with peroxy radicals generated by the thermal decomposition of azodiisobutyronitrile was studied at 75 °C in ethanol, propan-2-ol, and dimethyl sulfoxide. The stoichiometry of the reaction is 1: 1. The reaction product is dihydro-6-hydroxy-6-methylpyrimidine-2,4,5-trione in an anhydrous solvent or dihydro-5,5,6-trihy-droxy-6-methylpyrimidine-2,4-dione in the presence of water. The rate constant for the reaction of 5-hydroxy-6-methyluracil with the peroxy radicals is ∼10⁸ L mol⁻¹ s⁻¹.     

Acid-Base Properties of 5-Hydroxy-1,3,6-trimethyluracil in Aqueous Solutions

Russian Journal of General Chemistry - 5-Hydroxy-1,3,6-trimethyluracil has been studied using 1H, 13C, and 15N NMR as well as UV spectroscopy. The constants and thermodynamic characteristics of its...     

A Procedure for Preparing Effective Immunomodulators and Antioxidants: 5-Hydroxy-6-methyluracil and 5-Hydroxy-1,3,6-trimethyluracil

Russian Journal of Applied Chemistry - 5-Hydroxy-6-methyluracil is an acting agent of Oxymethyluracilum drug, an immunostimulator with a broad spectrum of pharmacological activity. Its synthesis is...     

Thermochemical study of 5-methyluracil, 6-methyluracil, and 5-nitrouracil

The standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, for 5-methyluracil, 6-methyluracil, and 5-nitrouracil were derived from the values of the standard massic energies of combustion measured by static bomb combustion calorimetry. The results obtained together with literature values of the enthalpies of sublimation yielded the standard molar enthalpies of formation, in gaseous phase, at T = 298.15 K. These values are discussed in the terms of structural enthalpic increments.     

Thermochemical study of 5-methyluracil, 6-methyluracil,and 5-nitrouracil

The standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, at T = 298.15 K, for 5-methyluracil, 6-methyluracil, and 5-nitrouracil were derived from the values of the standard massic energies of combustion measured by static bomb combustion calorimetry. The results obtained together with literature values of the enthalpies of sublimation yielded the standard molar enthalpies of formation, in gaseous phase, at T = 298.15 K. These values are discussed in the terms of structural enthalpic increments.     

Electrochemical Behavior of Sulfur in Aqueous Alkaline Solutions

Russian Journal of Physical Chemistry A - The kinetics and mechanism of the electrode oxidation-reduction of sulfur on an electrically conductive sulfur–graphite electrode in an alkaline...     

Photocatalytic Oxidation of Thiocianates in Aqueous Solutions

Russian Journal of Applied Chemistry - The kinetic patterns of the photocatalytic oxidation of thiocyanates by persulfate under the influence of quasi-solar ultraviolet radiation (UV) were...     

A new synthesis of 5-hydroxy-6-methyluracil

Dehydration of 5,6-dihydro-5,6-dihydroxy-6-methyl- and 5,6-dihydro-5,6-dihydroxy-1,3,6-trimethyl-uracil in 0.4 M aqueous sulfuric acid gives 5-hydroxy-6-methyl- and 5-hydroxy-1,3,6-trimethyluracil in quantitative yields. Two possible mechanisms have been examined using the mPW1k/6-311+G(2df,2pd)//mPW1k/6-31+G(d,p) method for the transformation of methylated and non-methylated 5,6-dihydro-5,6-dihydroxy-6-methyluracils into the corresponding 5-hydroxy-6-methyluracils. The first is a hydride C5-C6 shift occurring in concert with the loss of a water molecule and formation of the corresponding protonated 5,6-dihydro-5-oxo-6-methyluracils. The second is an acid-catalyzed dehydration reaction to yield 5-hydroxy-6-methyluracils. The calculations demonstrated that the second pathway was energetically most favorable.     

Thermal-Plasma Jet Oxidation of Phenol in Aqueous Solutions

Chemical transformations occurring in distilled water and aqueous phenol solutions during treatment with an oxygen plasma jet were experimentally studied. The phenol conversion by plasma treatment of its aqueous solutions was found to be mainly due to reactions involving free radicals.     

The Benzoylation of 6-Methyluracil and 5-Nitro-6-methyluracil

6-Methyluracil and 5-nitro-6-methyluracil react with variable molar quantities of benzoyl chloride in acetonitrile-pyridine at room temperature to give I-N, 3-N-dibenzoyl-6-methyluracil 3b and l-N-benzoyl-5-nitro-6-methyluracil 4b. The reactive rates of debenzoylation of 3b and 4b were investigated.     

Kinetics of Polyol Oxidation by Ozone in Aqueous Solutions

Spectrophotometry is applied to study the oxidation of ethylene glycol, triethylene glycol, glycerol, etriol, pentaerithritol and mannitol by ozone in aqueous solutions at 277–304 K. Rate constants and activation parameters of the reaction are measured. It is proposed that the oxidation of these alcohols by ozone occurs via the same mechanism. The formation of an intermediate complex is a rate-limiting step in the case of diols; the decomposition of the complex is a rate-limiting step for tri- to hexatomic alcohols.     

Radiation-Stimulated Oxidation Reactions of Oxo Anions in Aqueous Solutions

The common features of oxidation processes for inorganic oxo anions under the action of ionizing radiation are considered. The radiation-stimulated oxidation reactions of lower nitrogen, phosphorus, arsenic, and sulfur oxo anions occur via a chain mechanism. The kinetics of these processes can be explained in terms of the peroxide oxidation theory. A correlation between the kinetic and thermodynamic characteristics of the assumed rate-determining step is observed, thus proving the uniformity of oxidation mechanisms. Ways to use the processes of interest in practice are proposed.     

Synthesis and characterization of 5-bromo-3-sec-butyl-6-methyluracil

A new synthetic method for 5-bromo-3-sec-butyl-6-methyluracil (Bromacil) using 2-bromobutane and urea as starting materials is described. The synthesis involved condensation, cyclization and bromination with a total yield of 60%. The structure of Bromacil was determined by ¹H NMR, ¹³C NMR and IR spectroscopy. __________ Translated from Journal of Shandong University (Natural Science Edition), 2007, 42(7): 9–12 [译自: 山东大学学报(自然科学版)]     

流光放电等离子体液相氧化亚硫酸铵

在氨-硫铵法烟气脱硫中, 一个关键环节是将副产物的四价硫S(IV)氧化为六价硫S(VI). 采用可规模化的流光放电液相氧化技术, 通过交直流叠加(AC/DC)电源, 激发气体放电产生等离子体对氨法脱硫高浓度的亚硫酸铵进行氧化. 实验测量了该氧化过程与溶液浓度、放电功率密度、溶液pH值、温度以及传质效率因子等各种参数的关系. 研究表明, 在亚硫酸铵摩尔浓度为3 mol·L-1时, 可以获得有实用价值的反应速率, 摩尔能耗减低到50 Wh·mol-1以下, 显示出很好的应用前景.     

Oxidation of 5-hydroxy-6-methyluracil with molecular oxygen in the presence of copper(II) chloride in aqueous solution

Oxidation of 5-hydroxy-6-methyluracil with molecular oxygen in the presence of copper(II) chloride involves formation of a 2 : 1 complex with copper(II). The rates of consumption of initial 5-hydroxy-6-methyluracil and oxygen were determined in the temperature range from 40 to 80°C. A probable reaction mechanism implies fixation and activation of molecular oxygen on the copper(II) complex with 5-hydroxy-6-methyluracil with formation of active oxygen species that are responsible for hydroxylation of the double C⁵=C⁶ bond in the uracil molecule.