Air H2O2 Research Articles

Strong-Acid-Catalyzed Formation of Crystalline LiNbO3 at Low Ambient Temperatures.

A crystalline LiNbO3 material was synthesized at 80 °C by an optimized sol-gel method using a double alkoxide alcoholic solution in the presence of hydrogen peroxide (H2O2) and strong acids. The same reaction in the presence of water or acetic acid resulted in amorphous powders with fewer impurities but which crystallized only at 450 °C and higher temperatures. The purity of the crystalline material obtained at 80 °C is strongly dependent on the Li/Nb molar ratio used for the reaction. It appears that the combination of strong acids with H2O2 in air generates perfect conditions for the synthesis of low-temperature crystalline lithium niobate oxide derivatives and can be extended to various other metal oxides. The developed synthetic method opens the potential for the coating of low-melting-point conductive polymer materials with LiNbO3 crystalline films.

UV-Light-Induced Water Condensation in Air and the Role of Hydrogen Peroxide

Abstract We report the UV-light-induced formation of water aerosol/droplets in air based on laser-light scattering measurements, differential mobility analyses and cavity ring-down laser spectroscopy (CRDS), and propose a mechanism. It was shown that UV-light (185 nm) irradiation of air within a soap bubble rapidly produced water droplets under supersaturated conditions. Multiple UV irradiation cycles were demonstrated to increase particle sizes in a controlled reaction chamber. We propose that the reaction mechanism is initiated by oxygen (O2) photodissociation and ozone (O3) formation and further photodissociation of O3 leads to sequential dark reactions, generating hydrogen peroxide (H2O2) as a hygroscopic stable product. Exciting excess O3 in wet air with mid-UV radiations (254 nm) was also demonstrated to produce water particles, indicating that this series of reactions can be started at an intermediate stage using a longer wavelength of UV light. For the first time, it was demonstrated that H2O2 in air is a precursor of the initial nucleation of water with two different aerosol formation schemes at 263 K: a) from a mixture of H2O2 and water vapor in dark and b) from a mixture of O3 and water vapor by mid-UV (266 nm) light irradiation. These results indicate that H2O2 can capture water molecules and form water particles.

Paired Bacillus anthracis Dps (Mini-ferritin) Have Different Reactivities with Peroxide

Dps (DNA protection during starvation) proteins, mini-ferritins in the ferritin superfamily, catalyze Fe(2+)/H(2)O(2)/O(2) reactions and make minerals inside protein nanocages to minimize radical oxygen-chemistry (metal/osmotic/temperature/nutrient/oxidant) and sometimes to confer virulence. Paired Dps proteins in Bacillus, rare in other bacteria, have 60% sequence identity. To explore functional differences in paired Bacilli Dps protein, we measured ferroxidase activity and DNA protection (hydroxyl radical) for Dps protein dodecamers from Bacillus anthracis (Ba) since crystal structures and iron mineralization (iron-stain) were known. The self-assembled (200 kDa) Ba Dps1 (Dlp-1) and Ba Dps2 (Dlp-2) proteins had similar Fe(2+)/O(2) kinetics, with space for minerals of 500 iron atoms/protein, and protected DNA. The reactions with Fe(2+) were novel in several ways: 1) Ba Dps2 reactions (Fe(2+)/H(2)O(2)) proceeded via an A(650 nm) intermediate, with similar rates to maxi-ferritins (Fe(2+)/O(2)), indicating a new Dps protein reaction pathway, 2) Ba Dps2 reactions (Fe(2+)/O(2) versus Fe(2+)/O(2) + H(2)O(2)) differed 3-fold contrasting with Escherichia coli Dps reactions, with 100-fold differences, and 3) Ba Dps1, inert in Fe(2+)/H(2)O(2) catalysis, inhibited protein-independent Fe(2+)/H(2)O(2) reactions. Sequence similarities between Ba Dps1 and Bacillus subtilis DpsA (Dps1), which is regulated by general stress factor (SigmaB) and Fur, and between Ba Dps2 and B. subtilis MrgA, which is regulated by H(2)O(2) (PerR), suggest the function of Ba Dps1 is iron sequestration and the function of Ba Dps2 is H(2)O(2) destruction, important in host/pathogen interactions. Destruction of H(2)O(2) by Ba Dps2 proceeds via an unknown mechanism with an intermediate similar spectrally (A(650 nm)) and kinetically to the maxi-ferritin diferric peroxo complex.

Zirconium complexes having a chiral phosphanylamide in the co-ordination sphere

The chiral phosphanylamido ligand, (N(CHMePh)(PPh2))-, has been introduced into co-ordination chemistry. As starting material the oily amines HN(R-*CHMePh)(PPh2)(1a) and HN(S-*CHMePh)(PPh2)(1b) were used. To reconfirm their absolute structure, 1b was oxidized with H2O2 in air to obtain HN(S-*CHMePh)(P(O)Ph2)(2) as a solid compound. The solid-state structure of 2 was established by single-crystal X-ray diffraction. The lithium salts of both enantiomers Li(N(R-*CHMePh)(PPh2))(3a) and Li(N(S-*CHMePh)(PPh2))(3b) were prepared by deprotonation reaction of 1a,b. Compounds 3a,b were further reacted with zirconocen dichloride to give the chiral metallocenes [(eta5-C5H5)2Zr(Cl)(eta2-N(R-*CHMePh)(PPh2))](4a) and [(eta5-C5H5)2Zr(Cl)(eta2-N(S-*CHMePh)(PPh2))](4b). In an alternative approach to give chiral zirconium compounds, the neutral amine 1b was reacted with [(PhCH2)4Zr] to give the enantiomeric pure complex [(PhCH2)3Zr(eta2-N(S-*CHMePh)(PPh2))](5). The solid-state structures of all zirconium complexes were determined by single-crystal X-ray diffraction.

Synthesis, Characterization and Optimum Reaction Conditions of Oligo-N, N -bis (2-hydroxy-1-naphthalidene) Thiosemicarbazone

The oxidative polycondenzation reaction conditions of N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone (HNTSC) using air oxygen, H2O2 and NaOCl were studied in an aqueous alkaline medium between 50–90 °C. Oligo-N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone was characterized by 1H-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. Solubility testing of oligomer was investigated using organic solvents such as DMF, THF, DMSO, methanol, ethanol, CHCl3, CCl4, toluene acetonitrile, ethyl acetate, concentrated H2SO4 and an aqueous alkaline solution. Using NaOCl, H2O2 and air O2 oxidants, conversion to oligo-N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone (OHNTSC) of N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone was found to be 85, 80 and 76%, respectively, in an aqueous alkaline medium. According to the SEC analyses, the number-average molecular weight, weight-average molecular weight and polydispersity index values of OHNTSC synthesized were found to be 1050 g mol−1 1715 g mol−1 and 1.63, using NaOCl, and 2137, 2957 g mol−1 and 1.38, using air O2 and 2155 g mol−1 4164 g mol−1 and 1.93, using air H2O2, respectively. Also, TG analysis was shown to be unstable of oligo-N, N′-bis (2-hydroxy-1-naphthalidene) thiosemicarbazone against thermo-oxidative decomposition. The weight loss of OHNTSC was found to be 97.29% at 900 °C.

Synthesis, characterization, and optimum reaction conditions of oligo‐2‐[(pyridine‐2‐yl‐methylene) amino] phenol

AbstractThe reaction conditions of the oxidative polycondensation of 2‐[(pyridine‐2‐yl‐methylene) amino] phenol (2‐PMAP) with air O2, H2O2, and NaOCl were studied in an aqueous alkaline medium between 60 and 90 °C. Oligo‐2‐[(pyridine‐2‐yl‐methylene) amino] phenol (O‐2‐PMAP) was characterized with 1H NMR, Fourier transform infrared, ultraviolet–visible, size exclusion chromatography (SEC), and elemental analysis techniques. Moreover, solubility testing of the oligomer was performed in polar and nonpolar organic solvents. With the NaOCl, H2O2, and air O2 oxidants, the conversions of 2‐PMAP into O‐2‐PMAP were 98, 87, and 62%, respectively, in an aqueous alkaline medium. According to SEC, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of O‐2‐PMAP were 2262 g mol−1, 2809 g mol−1, and 1.24 with NaOCl, 3045 g mol−1, 3861 g mol−1, and 1.27 with air O2, and 1427 g mol−1, 1648 g mol−1, and 1.16 with air H2O2, respectively. Also, thermogravimetric analysis showed that O‐2‐PMAP was stable against thermooxidative decomposition. The weight loss of O‐2‐PMAP was 96.68% at 900 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2717–2724, 2004

Oxidations by the system “hydrogen peroxide - manganese(IV) complex - acetic acid” — Part II. Hydroperoxidation and hydroxylation of alkanes in acetonitrile

Higher alkanes (cyclohexane, n-pentane, n-heptane, methylbutane, 2- and 3-methylpentanes, 3-methylhexane, cis- and trans-decalins) are oxidized at 20 °C by H2O2 in air in acetonitrile (or nitromethane) solution in the presence of the manganese(IV) salt [L2Mn2O3](PF6)2 (L = 1,4,7-trimethyl-1,4-7-triazacyclononane) as the catalyst. An obligatory component of the reaction mixture is acetic acid. Turnover numbers attain 3300 after 2 h, the yield of oxygenated products is 46% based on the alkane. The oxidation affords initially the corresponding alkyl hydroperoxide as the predominant product, however later these compounds decompose to produce the corresponding ketones and alcohols. Regio- and bond selectivities of the reaction are high: C(1) : C(2) : C(3) : C(4) ≈ 1 : 40 : 35 : 35 and 1° : 2° : 3° is 1 : (15–40) : (180–300). The reaction with both isomers of decalin gives (after treatment with PPh3) alcohols hydroxylated in the tertiary positions with the cis/trans ratio of ∼ 2 in the case of cis-decalin, and of ∼ 30 in the case of trans-decalin (i.e. in the latter case the reaction is stereospecific). Light alkanes (methane, ethane, propane, normal butane and isobutane) can be also easily oxidized by the same reagent in acetonitrile solution, the conditions being very mild: low pressure (1–7 bar of the alkane) and low temperature (−22 to +27 °C). Catalyst turnover numbers attain 3100, the yield of oxygenated products is 22% based on the alkane. The yields of oxygenates are higher at low temperatures. The ratio of products formed (hydroperoxide: ketone: alcohol) depends very strongly on the conditions of the reaction and especially on the catalyst concentration (at higher catalyst concentration the ketone is predominantly produced).

Acute exposure to hair bleach causes airway hyperresponsiveness in a rabbit model.

Ammonium persulphate (APS) and hydrogen peroxide (H2O2) are used as oxidants in many industrial processes and are the main constituents of standard hair bleaching products. In a previous study, it was demonstrated that aerosols of APS induce alterations in airway responsiveness. The present study examined whether exposure for 4 h to a hair bleach composition (containing APS, potassium persulphate and H2O2) or H2O2 could induce airway hyperresponsiveness and/or an obstructive ventilation pattern in a rabbit model. Exposure to the aerosols altered neither baseline airway resistance, dynamic elastance, slope of inspiratory pressure generation nor arterial blood pressure and blood gas measurements. Similarly to APS, hair bleach aerosols containing > or =10.9 mg x m(-3) persulphate (ammonium and potassium salt) in air and > or =1.36 mg x m(-3) H2O2 in air caused airway hyperresponsiveness to acetylcholine after 4 h of exposure. Aerosolized H2O2 (> or =37 mg x m(-3) in air) did not influence airway responsiveness to acetylcholine. The results demonstrate that hair bleaching products containing persulphates dissolved in H2O2 cause airway hyperresponsiveness to acetylcholine in rabbits.

Interaction of ozone and hydrogen peroxide in water: Implications for analysis of H2O2 in air

We have attempted to measure gaseous H2O2 in air using an aqueous trapping method. With continuous bubbling, H2O2 levels in the traps reached a plateau, indicating that a state of dynamic equilibrium involving H2O2 destruction was established. We attribute this behavior to the interaction of ozone and its decomposition products (OH, O3−) with H2O2 in aqueous solution. This hypothesis was investigated by replacing the air stream with a mixture of N2, O2 and O3. The results of this experiment show that H O was both produced and destroyed in the traps. These results have led us to question the validity of techniques which employ aqueous traps to measure H2O2 in air.