Determination of organic peracids and hydrogen peroxide in mixtures

A simple method for the determination of organic peracids and hydrogen peroxide in mixtures is presented. The method is based on the instantaneous reaction of peracids with neutral potassium iodide and on the formation of a stable complex between hydrogen peroxide and titanyl ions. This complex is decomposed with sodium fluoride and the ensuing reaction with iodide is accelerated with molybdic acid. The influence of the different additives on the analytical results has been studied.     

Preparation of pure hydrogen peroxide and anhydrous peroxide solutions from crystalline serine perhydrate

Hydrogen peroxide is one of the most versatile oxidation reagents, still it has not fully been exploited by synthetic chemists since anhydrous (let alone pure) hydrogen peroxide requires hazardous preparation protocols. We have recently reported on the crystallization of serine and other amino acid perhydrates, thus paving the way for a new method for laboratory-scale production of anhydrous hydrogen peroxide solutions. Serine is insoluble in most organic solvents (e.g., methanol, ethyl acetate, and methyl acetate) that readily dissolve hydrogen peroxide. Moreover, since the adduct of hydrogen peroxide and serine is unstable in these organic solvents, crystalline serine perhydrate readily decomposes to give anhydrous solutions of hydrogen peroxide and crystalline precipitate of the amino acid. This procedure can then yield an anhydrous hydrogen peroxide solution in a single step. Moreover, filtration of the amino acid, and room temperature evaporation of the volatile solvent (e.g., methyl acetate), yields over 99% hydrogen peroxide.     

Transformations of furoyl peroxide and hydroperoxide in the presence of water and hydrogen peroxide

In the presence of water, furoyl peroxide and hydroperoxide are hydrolyzed to pyromucic acid and hydrogen peroxide, between which there is a partial reaction.     

On the formation of hydrogen peroxide in water microdroplets

Recent reports on the formation of hydrogen peroxide (H₂O₂) in water microdroplets produced via pneumatic spraying or capillary condensation have garnered significant attention. How covalent bonds in water could break under such mild conditions challenges our textbook understanding of physical chemistry and water. While there is no definitive answer, it has been speculated that ultrahigh electric fields at the air–water interface are responsible for this chemical transformation. Here, we report on our comprehensive experimental investigation of H₂O₂ formation in (i) water microdroplets sprayed over a range of liquid flow-rates, (shearing) air flow rates, and air composition, and (ii) water microdroplets condensed on hydrophobic substrates formed via hot water or humidifier under controlled air composition. Specifically, we assessed the contributions of the evaporative concentration and shock waves in sprays and the effects of trace O₃(g) on the H₂O₂ formation. Glovebox experiments revealed that the H₂O₂ formation in water microdroplets was most sensitive to the air–borne ozone (O₃) concentration. In the absence of O₃(g), we could not detect H₂O₂(aq) in sprays or condensates (detection limit ≥250 nM). In contrast, microdroplets exposed to atmospherically relevant O₃(g) concentration (10–100 ppb) formed 2–30 µM H₂O₂(aq), increasing with the gas–liquid surface area, mixing, and contact duration. Thus, the water surface area facilitates the O₃(g) mass transfer, which is followed by the chemical transformation of O₃(aq) into H₂O₂(aq). These findings should also help us understand the implications of this chemistry in natural and applied contexts.

A. Gallo Jr, H. Mishra et al., pinpoint the origins of the spontaneous H₂O₂ formation in water microdroplets formed via spraying or condensation, i.e., without the addition of electrical energy, catalyst, or co-solvent.     

The kinetics of hydrogen peroxide initiated polymerisation of methacrylamide

A kinetic study of the aqueous polymerisation of methacrylamide initiated by hydrogen peroxide has shown that the polymerisation proceeds in two stages. The rate of polymerisation up to about 16% conversion is represented by the equation

Within this period, the hydrogen peroxide is completely consumed and a hydroperoxide of methacrylamide is formed. Subsequently this hydroperoxide initiates polymerisation.     

Oscillatory kinetics and mechanism of the chromate catalyzed decomposition of hydrogen peroxide

Oscillatory change of pH occurs during the chromate-catalyzed decomposition of hydrogen peroxide in a weakly acidic medium at elevated temperature and at high initial concentration of hydrogen peroxide. In a closed system, there are only two or three periods, but sustained oscillation occurs in a CSTR. In a CSTR bistability is also found. In closed systems the temperature exhibits a great maximum (up to 15°C increase), in a CSTR sustained oscillation occurs at a constant stationary temperature.     

Decomposition of solid amorphous hydrogen peroxide by ion irradiation

We present laboratory studies of the radiolysis of pure (97%) solid H2O2 films by 50 keV H+ at 17 K. Using UV-visible and infrared reflectance spectroscopies, a quartz-crystal microbalance, and a mass spectrometer, we measured the absolute concentrations of the H2O, O2, H2O2, and O3 products as a function of irradiation fluence. Ozone was identified by both UV and infrared spectroscopies and O2 from its forbidden transition in the infrared at 1550 cm(-1). From the measurements we derive radiation yields, which we find to be particularly high for the decomposition of hydrogen peroxide; this can be explained by the occurrence of a chemical chain reaction.     

On the kinetics and the mechanism of hydrogen peroxide decomposition with silica-supported metallo-porphyrins

The decomposition of hydrogen peroxide was carried out with four kinds of silica-supported metallo-porphyrins. By kinetic studies, the reaction rates are expressed as follows with CuTPP and CoTPP systems, respectively.

Reaction mechanisms were proposed on the basis of the kinetic data. The rate differences with various metallo-pophyrins can be explained by different processes for the formation of intermediates.     

Decay of vibrational coherence in ortho-para mixtures of solid hydrogen

Hydrogen crystals were pumped by stimulated Raman gain into coherent superpositions of the ground and 2 v = 1 vibrational exciton state and its amplitude monitored by coherent anti-Stokes scattering. The resulting non-exponential and temperature independent (1.6–4.2 K) decays, for o-H₂ concentrations between 0.22 and 2.7%, were attributed to compositional scattering.     

The kinetics of iodide oxidation by hydrogen peroxide in acid solution

The kinetics of the complex reaction between I⁻ and H₂O₂ in acid media was investigated. The particular attention was focused on the determination of the rate constant of the reaction between HIO and H₂O₂ involved in the investigated complex process. The examination of the whole kinetics was performed by simultaneously monitoring the evolution of O₂ pressure, I₃⁻ and I⁻ concentrations. We modeled the behavior of experimentally followed components based on Liebhafsky’s research. Our preliminary results suggest a significantly higher rate constant (3.5 × 10⁷ M⁻¹ s⁻¹) of the reaction between HIO and H₂O₂ as those proposed in the literature.     

Fluorimetric determination of hydrogen peroxide in water using acetaminophen

A fluorimetric procedure for the determination of hydrogen peroxide, based on the oxidation of acetaminophen with hydrogen peroxide in acidic medium, is described. The calibration graph was linear in the range 5.0 x 10(-8) - 2.4 x 10(-5) M hydrogen peroxide at an emission wavelength of 333 nm with excitation at 298 nm. The method has been applied to the determination of hydrogen peroxide in rain water, and the recoveries in milk samples were good.     

Role of water in the oxidation of furfural with hydrogen peroxide

The oxidation of furfural with hydrogen peroxide in water and in absolute ether containing small amounts of water was studied. It was found that water inhibits the formation of furfuryl hydroxyhydroperoxide but promotes the buildup of acids. The accumulated acids play a catalytic role in all stages of the process.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1453–1456, November, 1972.     

Simultaneous hydrogen and peroxide production by photocatalytic water splitting

Photocatalytic oxidation of water is a promising method to realize large-scale H₂O₂ production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO₂(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H₂ and H₂O₂ production. Both H₂ and H₂O₂ are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g^–1 h^–1 (first 1 h) for H₂ and H₂O₂, respectively, which is much higher than that of a commercial Pt/TiO₂(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H₂O₂, compared with the four-electron oxidation of water to O₂.     

The kinetics and mechanism of gas-phase N-oxidation of pyridine with hydrogen peroxide

The kinetics of N-monooxidation of 4-vinylpyridine as a π-deficient heteroaromatic compound under the conditions of gas-phase free-radical chain oxidation was studied. The experimental interference kinetic curves of synchronous hydrogen peroxide decomposition and 4-vinylpyridine N-oxidation reactions were obtained. The region of selective N-oxidation was determined and optimum conditions of N-oxide preparation found. The most probable mechanism was suggested. According to this mechanism, a key role in the free-radical N-oxidation of the substrate and its synchronization with the H₂O₂ decomposition reaction was played by HO₂ radicals.     

Dielectric dispersion in water + 2-hydroxypyridine solid mixtures

The complex electric permittivity was measured in water + 2-hydroxypyridine (2HP) solid mixtures as a function of concentration, temperature and frequency. Just after freezing of diluted mixtures, (mole fraction of 2HP < 0.2) pronounced dielectric dispersion in the MHz region was observed. The dispersion disappears on cooling between -30 and -40 degrees C in a first-order phase transition. The dispersion was explained in terms of the movement of a guest molecule (2HP) in a clathratelike structure of ice.     

Comparative photodegradation study of atrazine and desethylatrazine in water samples containing titanium dioxide/hydrogen peroxide and ferric chloride/hydrogen peroxide

Results are reported for a comparative photodegradation study of atrazine and desethylatrazine in water using TiO2/H2O2, FeCl3/H2O2, and photolysis. Deionized water and ground water spiked with atrazine or desethylatrazine at 36 micrograms/L were irradiated by using a xenon arc lamp and/or sunlight. After irradiation, the water samples containing the spiked pesticides were preconcentrated by using C18 solid-phase extraction disks and analyzed by gas chromatography with nitrogen-phosphorus and mass spectrometric detection. A relative percentage of 7% desethylatrazine was detected in samples removed after 20 and 4 min of sensitized photodegradation with TiO2 and Fe3+, respectively. Atrazine and desethylatrazine did not degrade when solar irradiation (in winter) and deionized water were used. Atrazine degraded faster than desethylatrazine when a xenon arc lamp or sunlight plus FeCl3 was used, with half-lives varying from 5 to 11 min and from 19 to 26 min, respectively. In other photodegradation experiments, the degradation of atrazine was slightly higher than that of desethylatrazine. This study shows that desethylatrazine has slightly higher stability than atrazine in environmental water samples; this stability accounts for the frequent detection of desethylatrazine together with atrazine in natural waters.     

Solubility of light hydrocarbons and their mixtures in pure water under high pressure

New solubility data of methane, ethane, n-butane and their mixtures in pure water are obtained at 344.25 K, from 2.5 to 100 MPa. The results agree well with those of the literature in the case of pure hydrocarbons in water, but differ significantly for hydrocarbon mixtures. In contrast to the conclusion reached by Amirijafari and Campbell [B. Amirijafari, J. Campbell, Solubility of gaseous hydrocarbon mixtures in water, Soc. Pet. Eng. J. (1972) 21–27.], the experimental solubility data of methane–ethane mixtures shows an ideal solution behavior, while the solubility data of methane–n-butane mixtures shows a weaker non-ideality than that observed by McKetta and Katz [J.J. McKetta, D.L. Katz, Methane–n-butane–water system in two-and three-phase regions, Ind. Eng. Chem. 40 (1948) 853–863]. The pure hydrocarbon solubility data are satisfactorily correlated using the Soreide and Whitson modification [I. Soreide, C.H. Whitson, Peng–Robinson predictions for hydrocarbons, CO2, N2, and H2S with pure water and NaCl brine, Fluid Phase Equilib. 77 (1992) 217–240] of the Peng–Robinson equation of state.     

The kinetics of complex formation between Ti(IV) and hydrogen peroxide

The kinetics of the formation of the titanium‐peroxide [TiO²⁺₂] complex from the reaction of Ti(IV)OSO₄ with hydrogen peroxide and the hydrolysis of hydroxymethyl hydroperoxide (HMHP) were examined to determine whether Ti(IV)OSO₄ could be used to distinguish between hydrogen peroxide and HMHP in mixed solutions. Stopped‐flow analysis coupled to UV‐vis spectroscopy was used to examine the reaction kinetics at various temperatures. The molar absorptivity (ε) of the [TiO²⁺₂] complex was found to be 679.5 ± 20.8 L mol^?1 cm^?1 at 405 nm. The reaction between hydrogen peroxide and Ti(IV)OSO₄ was first order with respect to both Ti(IV)OSO₄ and H₂O₂ with a rate constant of 5.70 ± 0.18 × 10⁴ M^?1 s^?1 at 25°C, and an activation energy, E_a = 40.5 ± 1.9 kJ mol^?1. The rate constant for the hydrolysis of HMHP was 4.3 × 10^?3 s^?1 at pH 8.5. Since the rate of complex formation between Ti(IV)OSO₄ and hydrogen peroxide is much faster than the rate of hydrolysis of HMHP, the Ti(IV)OSO₄ reaction coupled to time‐dependent UV‐vis spectroscopic measurements can be used to distinguish between hydrogen peroxide and HMHP in solution. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 457–461, 2007     

Thallimetric photochemical oxidation in titrimetric and spectrophotometric methods for the analysis of mixtures of oxalate and hydrogen peroxide

Thallium(III) in the presence of bromide photochemically oxidizes oxalate and hydrogen peroxide, whereas in the presence of a large excess of chloride, only oxalate is oxidized. Two procedures are based on these observations. In the titrimetric method (applied to mmol amounts of analytes) the thallium(I) formed is determined with bromate. In the spectrophotometric procedure (μmol amounts of analytes) unreduced thallium(III) is determined at 260 nm. In each case measurements are made after reaction under both conditions, so that both analytes can be determined.