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The time-dependent chemisorption of 2-chlorophenol on a fumed silica surface is studied in situ from 200 to 500 degree Celsius using a temperature-controlled dosing cell and FTIR absorption spectroscopy. 2-Chlorophenol is found to chemisorb at isolated and geminal surface hydroxyl sites.

A 30-reaction core kinetic model is developed that accounts for the major features in the homogeneous formation of polychlorinated dibenzofurans (PCDF) from the high-temperature oxidation of 2,4,6-trichlorophenol (TCP). The conversion of TCP to 2,4-dichlorophenol provides an ortho hydrogen, which is necessary for the formation of PCDF.

The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) via a Cu(II)O-mediated reaction of 2-chlorophenol is studied as a packed bed reactor over a temperature range of 200-500 degrees Celsius. The results of the study indicate the presence of a carbon-centered phenoxyl radical on the surface, which is attributed to chemisorptions of 2-MCP at a copper oxide site followed by electron transfer to Cu(II) to form Cu (I), and a phenoxyl radical.

Copper chloride- and copper oxide-impregnated borosilicates have been found to be effective catalysts in acetylene condensation/chlorination reactions. Copper chloride borosilicates were found to be effective at temperatures above 150 degrees centigrade while copper oxide borosilicates were found effective only at temperatures higher than 300 degrees centigrade. Optimal temperatures for the two catalysts was pegged between 300 degrees centigrade and 400 degrees centigrade.

Abstract Background Increased asthma risk/exacerbation in children and infants is associated with exposure to elevated levels of ultrafine particulate matter (PM). The presence of a newly realized class of pollutants, environmentally persistent free radicals (EPFRs), in PM from combustion sources suggests a potentially unrecognized risk factor for the development and/or exacerbation of asthma. Methods Neonatal rats (7-days of age) were exposed to EPFR-containing combustion generated ultrafine particles (CGUFP), non-EPFR containing CGUFP, or air for 20 minutes per day for one week. Pulmonary function was assessed in exposed rats and age matched controls. Lavage fluid was isolated and assayed for cellularity and cytokines and in vivo indicators of oxidative stress. Pulmonary histopathology and characterization of differential protein expression in lung homogenates was also performed. Results Neonates exposed to EPFR-containing CGUFP developed significant pulmonary inflammation, and airway hyperreactivity. This correlated with increased levels of oxidative stress in the lungs. Using differential two-dimensional electrophoresis, we identified 16 differentially expressed proteins between control and CGUFP exposed groups. In the rats exposed to EPFR-containing CGUFP; peroxiredoxin-6, cofilin1, and annexin A8 were upregulated. Conclusions Exposure of neonates to EPFR-containing CGUFP induced pulmonary oxidative stress and lung dysfunction. This correlated with alterations in the expression of various proteins associated with the response to oxidative stress and the regulation of glucocorticoid receptor translocation in T lymphocytes.

Abstract Background Combustion generated particulate matter is deposited in the respiratory tract and pose a hazard to the lungs through their potential to cause oxidative stress and inflammation. We have previously shown that combustion of fuels and chlorinated hydrocarbons produce semiquinone-type radicals that are stabilized on particle surfaces (i.e. environmentally persistent free radicals; EPFRs). Because the composition and properties of actual combustion-generated particles are complex, heterogeneous in origin, and vary from day-to-day, we have chosen to use surrogate particle systems. In particular, we have chosen to use the radical of 2-monochlorophenol (MCP230) as the EPFR because we have previously shown that it forms a EPFR on Cu(II)O surfaces and catalyzes formation of PCDD/F. To understand the physicochemical properties responsible for the adverse pulmonary effects of combustion by-products, we have exposed human bronchial epithelial cells (BEAS-2B) to MCP230 or the CuO/silica substrate. Our general hypothesis was that the EPFR-containing particle would have greater toxicity than the substrate species. Results Exposure of BEAS-2B cells to our combustion generated particle systems significantly increased reactive oxygen species (ROS) generation and decreased cellular antioxidants resulting in cell death. Resveratrol treatment reversed the decline in cellular glutathione (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels for both types of combustion-generated particle systems. Conclusion The enhanced cytotoxicity upon exposure to MCP230 correlated with its ability to generate more cellular oxidative stress and concurrently reduce the antioxidant defenses of the epithelial cells (i.e. reduced GSH, SOD activity, and GPx). The EPFRs in MCP230 also seem to be of greater biological concern due to their ability to induce lipid peroxidation. These results are consistent with the oxidizing nature of the CuO/silica ultrafine particles and the reducing nature and prolonged environmental and biological lifetimes of the EPFRs in MCP230.

The spectral identification of newly prepared cyclopentadienyl and phenoxy radicals by using the gas-phase pyrolsis of phenol over a temperature range of 400-1000 degree Celsius is described.

The experimental results of temperature-dependent kinetics of the reactions of the hydroxyl radical with [nu]-propyl bromide ([C[H.sub.3]C[H.sub.2]C[H.sub.2]Br) and i-propyl bromide (C[H.sub.3]CHBrC[H.sub.3] over wide temperature ranges is presented.

Kinetic study of the gas-phase reaction of the hydroxyl radical with [Br.sub.2] was performed using a pulsed laser photolysis/pulsed-laser-induced fluorescence technique over a wide temperature range of 297-766 K, and at pressures between 6.68 and 40.29 kPa of helium. The calculated results demonstrated no correlation with pressure and showed negative temperature dependence with a slight negative curvature in the Arrhenius plot.

The reactions of hydroxyl radicals with hydrogen chloride is studied experimentally using a pulsed-laser photolysis/pulsed-laser-induced fluorescence technique over a wide range of temperatures, 298- 1015 K, and at pressures between 5.33 and 26.48 KPa. The potential-energy surface is studied using quantum chemical methods, and a transition-state theory model is developed for the reaction on the basis of calculations and experimental data.

The experimental and theoretical temperature-dependent kinetic investigation of the gas-phase reaction of the hydroxyl radical with molecular chlorine is described. The reactions of OH with molecular chlorine, methane and propane are studied experimentally using a pulsed laser photolysis/pulsed-laser-induced fluorescence technique over a wide range of temperature and pressure.