Free radical reactions of bromoform (BF) in air free and air saturated aqueous solutions. Effect of pH |
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| Affiliation: | 1. Department of Chemistry, Faculty of Arts and Science, Düzce University, 81620 Düzce, Turkey;2. Institute of Chemistry, University of Neuchatel, Avenue de Bellevaux 51, 2000 Neuchatel, Switzerland;3. Institut des Sciences et Ingénierie Chimique, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland;1. University of Opole, Faculty of Chemistry, 48, Oleska Str., 45-052 Opole, Poland;2. Institute of Physical Chemistry, Polish Academy of Sciences, 44/52, Kasprzaka, Str., 01-224 Warsaw, Poland;3. Faculty of Chemical and Process Engineering, Warsaw University of Technology, 1, Waryńskiego Street, 00-065 Warszawa, Poland;1. Department of Physics, 4513 Manhattan College Parkway Riverdale, New York 10471, USA;2. Faculty of Chemistry, Opole University, 48, Oleska Street, 45-052 Opole, Poland |
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| Abstract: | G(Br̄) and G(H2O2) have been reported in Ar, N2O and air saturated bromoform, containing 0.1 M t-butanol at various pHs. The results demonstrate an increase in G(Br̄) with increasing bromoform concentration and increasing pH. e-aq and Ḣ atoms react with bromoform to give Br̄, whereas ȮH radicals produce the t-butanol radical which interacts with bromoform and generates Br̄. This reaction is catalysed at acidic and alkaline pH. The results suggest that the reactivity of the primary radicals and t-butanol radical appear to be in the order e-aq > ḢȮH > ĊH2(CH3)2COH. Ḃr radicals formed as a result of reactions of dibromomethyl radical with bromoform, further react with bromoform to give Br̄.G(Br̄) values at high pH are attributed to the formation of a reactive intermediate BrOḢ- (Ḃr + OH-), which decays to Br̄ and ȮH at higher pH. G(Br̄) values are considerably higher in the presence of oxygen. This is because of the formation of peroxy radicals CHBr2Ȯ and CBr3Ȯ which decompose to Br̄ and CO, and Br̄ and CO2, respectively. High G(Br̄) values are found in the presence of isopropanol, ethanol and methanol suggesting a chain reaction. Rate constants for the reaction of ċHBr2 radical with isopropanol, ethanol and methanol have been measured as 553, 136 and 56 mol-1dm3s-1 respectively. G(H2O2) ∼ 0.6 in Ar and N2O saturated solution, and G(H2O2) ∼ 1.0 in air saturated solutions. |
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