Rate Constants for the Reactions of NO3 and SO4 Radicals with Oxalic Acid and Oxalate Anions in Aqueous Solution

Rate constants for the reactions of NO3 and SO4 radicals with oxalic acid and oxalate anions in aqueous solution have been measured using pulse radiolysis and laser flash photolysis.     

Radiolysis of 2-acetylfuran in 2-propanol in absence of atmospheric oxygen

Gamma radiolysis of 2-acetylfuran (AF) in 2-propanol, in absence of atmospheric oxygen, has been investigated. The radiation yields of hydrogen, methane at different doses as well as radiolytic products in solution were determined. The radiolytic products were determined by gas chromatography coupled with mass spectrometry. The mechanisms for formation of detected radiolytic products and the effect of (AF) concentration on hydrogen and methane yields are discussed.     

Effect of ascorbic acid and its derivatives on the radiation-chemical transformations of hydroxyl-containing organic compounds

The effect of ascorbic acid, 5,6-O-isopropylidyl-2,3-O-dimethylascorbic acid, and 2-O-glucopyranosylascorbic acid on the formation of main radiolysis products of ethanol and aqueous ethanol, ethylene glycol, α-methylglucopyranoside, and maltose solutions was studied by means of continuous radiolysis. The obtained results indicate that ascorbic acid effectively reacts with the carbon-centered hydroxyl-containing radicals derived from the substrates, thus decreasing the yield of their recombination and fragmentation products. It was found that the interaction of ascorbic acid and its derivatives with the carbon-centered radicals during the radiolysis of deaerated ethanol and its aqueous solutions may occur via both reducing and oxidizing mechanisms and that ascorbic acid in the aerated solutions acts as a hydrogen donor, reducing mainly the HO ₂ ^· radical to hydrogen peroxide.     

以草酸为电子给体在Pt-TiO2上光催化生成氢

 以草酸为电子给体,研究了在Pt－TiO2上光催化生成氢的反应．草酸的存在明显促进了生成氢的反应;二氧化钛负载Pt也明显提高了反应速率,Pt的最佳负载量为w（Pt）＝0．5％．草酸浓度对氢生成反应的影响符合Lang－muir关系式．最佳pH值为2～4．     

Radiolysis of nitrate-alcohol binary mixtures at pH 12

Gamma-radiolysis of alkaline binary mixtures of nitrate-alcohol (1-propanol and 1-butanol) has been investigated at a fixed pH of 12. The products of radiolysis, mainly nitrite, aldehyde and hydrogen peroxide were estimated. Also the effect of concentration of each species present in the mixture on the G-values of the products formed has been examined. The G-values of each of the products are found to be lower in basic medium in binary mixtures as compared to those obtained at neutral pH; other conditions being kept constant. However, the yields of products in nitrate solutions show higher values at basic pH in comparison with their counterparts at neutral pH. Results are explained on the basis of reaction mechanism that operates during the process of radiolysis, leading to the formation of the different products.     

Hydroxyl radical-mediated advanced oxidation processes for textile dyes: a comparison of the radiolytic and sonolytic degradation of the monoazo dye Acid Orange 7

Acid Orange 7, a textile azo dye, has been partially mineralized and degraded using -radiolysis and sonolysis. These two different advanced oxidation processes (AOP) are effective in producing OH radicals and cause complete destruction of the chromophore. The reaction mechanism of dye degradation has been probed by analyzing the reaction products with HPLC. In both cases, the final end products of degradation are oxalate and formate ions. The intermediates observed are all similar. While hydroxybenzenesulfonic acid is the major observed reaction intermediate in the oxidation processes, the pulse radiolysis studies indicate that the OH radical initiated pathway for attack occurs via the initial formation of 1,2-naphthaquinone and subsequent breakdown into oxalic acid.     

A radiation-chemical and quantum-chemical study of ascorbic acid interaction with α-hydroxyethyl radicals

The effect of ascorbic acid and its analogue 5,6-O-isopropylidenyl-2,3-O-dimethylascorbic acid (I), which has been synthesized for the purpose and does not contain mobile hydrogen atoms, on the formation of the products of continuous radiolysis of deaerated ethanol and its aqueous solutions has been studied. The ionization potentials, the molecular orbital energies, the enthalpies of homolytic dissociation of C-H and O-H bonds, and the enthalpies of H atom addition to the C=O group of the test compounds have been calculated by ab initio methods. The array of the experimental and calculated theoretical data suggests that both ascorbic acid in the undissociated form and compound I can oxidize α-hydroxyethyl radicals, whereas the monoanion of ascorbic acid acts as a reducing agent in the reactions with these transient radicals. The reduction of α-hydroxyethyl radicals in aqueous solutions by the ascorbic acid monoanion can follow both the hydrogen transfer and electron transfer mechanisms.     

Protective Effects in the Radiolysis of Acidified Hydrocarbon Solutions of Tributyl Phosphate

High Energy Chemistry - The effect of radiolysis and postradiation acid hydrolysis on the composition of the degradation products of tributyl phosphate (TBP, 30 wt %) in acidified Izopar-M has been...     

Radiolytic Gas Formation in Dilute Oxalic Acid Aqueous Solutions

The radiolytic gas formation in aqueous oxalic acid solutions was studied. The concentrations of ₂ and ₂, the gas phase constituents, were measured. It was found that gas evolution is mainly due to the degradation of both oxalic acid and its radiolysis products.     

Effects of tritium β-radiation and cobalt γ-radiation on vacuum oils

The radiolysis of vacuum oils was studied. The radiation-chemical yields of hydrogen varied over the range 1.6–3.2 depending on oil brand. A number of liquid radiolysis products were identified. It was found that, in the presence of oxygen, ketones were the main products of the radiation-induced oxidation of oils.     

The S2 emission characteristics of several organic sulfur compounds obtained by molecular emission cavity analysis and pyrolysis

Emission profiles of several organic sulfur compounds are investigated by modified molecular emission cavity analysis (MECA). Thiourea, 1,3-diethylthiourea, S-methyl- cysteine and taurine are pyrolyzed in a hydrogen stream and the pyrolytic products are determined by gas chromatography. The S₂ emission mechanism is discussed on the basis of emission profiles and the composition of the pyrolytic products. Although some compounds give multipeaked responses, the splitting disappears when a worn surface cavity is used or oxalic acid is added to the sulfur compound in the cavity. When the emission profile from thiourea is compared with that from 1,3-diethylthiourea, it is clear that the multipeaked response is due to quenching by degradation products of the latter compound. The main product of pyrolysis is hydrogen sulfide. The emission intensity is related to the yield of hydrogen sulfide in pyrolysis. As methylmercaptan was not detected in the pyrolysis products, it is suggested that the quenching by the organic fragments results from their hydrogen consumption rather than their reaction with sulfur species. The S₂ emission from sulfur-containing compounds is rapidly complete in the presence of oxalic acid, and it is suggested that such compounds are subject to reductive breakdown in the cavity.     

A study of radicals arising in the low-temperature radiolysis of thiophene and some of its derivatives

EPR was used to investigate the radicals formed by radiolysis of furan, thiophene, and some of their substitution products having the general formula C₄H₃RS, where R = Cl, Br, COOH, C(CH₃)₃, and of di-tert-butylthiophene. By analyzing the EPR spectra it is shown that radicals formed by radiolysis of furan, thiophene, their alkyl substitution products, and 2-thiophene carboxylic acid arise in primary radiation-chemical events with splitting of the C-H bond in both ring and side chain. Characteristic of the radiolysis of these compounds is formation of secondary radicals by addition of hydrogen atoms at the double bond of the heteroaromatic ring. The values of the hyperfine splittings in the spectra of the secondary radicals are, for protons of methylene group 32 e [positions 2(5)] or 40 e [positions 3(4)], and 13 e for protons of the thiophene ring. In radiolysis of 2-chlorothiophene and 3-bromothiophene the main products are radicals with the unpaired electron localized on the sulfur atom.     

光催化降解污染物制氢反应与原位红外表征

研究了在Pt/TiO2悬浮体系中单组分和双组分污染物为电子给体光催化分解水制氢反应. 比较了污染物甲醛、甲酸和草酸为电子给体光催化放氢反应效率，发现其活性为：草酸 >甲酸 >甲醛.原位ATR（衰减全反射）红外研究结果表明，光催化放氢活性与污染物吸附特性有关.还研究了草酸与甲酸双组分污染物体系的光解水放氢和污染物降解动力学，发现总的放氢和污染物降解速率与污染物组分在TiO2表面的吸附强度和溶液浓度有关.污染物在TiO2表面的竞争吸附决定了反应动力学.原位ATR-IR方法研究双组分混合物体系的吸附，直观地证实了上述结果.     

γ-Radiolysis of isobutanol and nitrate in aqueous solution

Radiolysis of isobutanol-nitrate aqueous solutions has been investigated in both aerated and deoxygenated solutions. Nitrate acts as a good scavenger for hydrated electrons. It gets reduced to nitrite during radiolysis. Alcohol, on the other hand, is used as a hydroxyl radical scavenger leading to the formation of aldehyde as the stable product. Nitrite, aldehyde and hydrogen peroxide formed as the stable products have been estimated in each system. Concentrations of both species (nitrate and alcohol) in the aqueous solution affect the yield of the products significantly. The observed G-values of the different products are accounted for by the mechanism proposed.     

The influence of iodine on the radiolysis of purex solvent

The effect of iodine on the radiolysis of TBP-dodecane-HNO₃ systems and the same systems containing the uranium, zirconium and palladium salts was examined. The results obtained indicate that the effect of iodine on the radiolysis products in the systems with and without uranium salt is similar. It has been found also that the effect of iodine on the retention of uranium and zirconium in organic phase depends on nitric acid concentration and is particularly high in the systems with low concentrations of HNO₃ containing uranium salt.     

Water adsorption around oxalic acid aggregates: a molecular dynamics simulation of water nucleation on organic aerosols

The phase behaviour of binary oxalic acid-water mixtures has been investigated by means of computer simulation techniques. Such mixtures play an important role in atmospheric processes, since the hydrogen bonding ability of oxalic acid molecules allows them to form aerosol particles. Water can in turn be readily adsorbed on the surface of such aerosol particles, which results in the formation of small ice grains. These grains are thus considered to be acting as cloud condensation nuclei, giving rise to the formation of ice clouds.     

Structure and reactions of reduction products in crystalline and polymeric materials by combining pulse radiolysis and ESR

The structure and the reactions of primary oxidation and reduction products in irradiated organic crystals and solid polymers have been investigated. The data from pulse radiolysis with nanosecond time resolution have been combined in a new manner with the data obtained by low-temperature irradiation and ESR spectroscopy. By this combination optical spectra have been assigned, reaction mechanisms have been studied and ESR components have been identified using the kinetic data from pulse radiolysis. The method has been particularly useful in the study of negative-ion radicals in carboxylic acid derivatives, of trapped electrons in polyhydroxy compounds, and of ionic species in polymers.     

草酸电还原反应机理的研究

以硫酸钠溶液作底液,用快速循环伏安和电势阶跃法研究了草酸在铅电极上的电还原机理,测定了草酸电还原第一步反应的动力学参数,并根据循环伏安图比较相同条件下草酸,乙醛酸和乙醇酸的还原峰峰电势,推断出草酸还原的中间产物.研究结果表明,草酸电还原遵从不可逆2电子EE反应机理.     

用双氧水绿色氧化环己酮合成己二酸的研究

以30%的双氧水为氧化剂, 钨酸钠与含N或O的双齿有机配体(草酸)形成的络合物为催化剂, 在无有机溶剂、无相转移剂的条件下, 研究了环己酮氧化制己二酸的反应. 研究结果表明, 用廉价的草酸为配体, 最佳反应条件为钨酸钠∶草酸∶环己酮∶30%的双氧水的物质的量比为2.0∶3.3∶100∶350, 在92 ℃下反应12 h, 可制得80.6%的己二酸; 用GC-MS跟踪了氧化过程中三种主要物质环己酮、己内酯及己二酸含量随反应时间的变化关系, 提出了其主要氧化机理为环己酮首先经Beayer-Villiger氧化反应生成己内酯, 己内酯进一步氧化成己二酸.     

用H2O2氧化苯乙烯合成苯甲酸

摘要：以30％H2O2做为氧化剂,钨酸钠与含O双齿有机配体(草酸)形成的络合物为催化剂,在无有机溶剂、无相转移剂的条件下,研究了苯乙烯氧化制苯甲酸的反应。研究结果表明,最佳反应条件为：苯乙烯100．0mmol,n(钨酸钠)：n(草酸)：n(苯乙烯)：n(30％H2O2)=2．0：3．2：100．0：440．0,于92℃反应24h,苯甲酸收率98．6％。用GC—MS跟踪了氧化过程中4种主要物质苯乙烯、1-苯基邻二醇、羟基苯乙酮及苯甲酸含量随反应时间的变化关系,提出了其主要氧化机理为苯乙烯经过环氧化反应、水解生成生成1-苯基邻二醇,1-苯基邻二醇再氧化为羟基苯乙酮、最后氧化为苯甲酸。