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Dehalogenation of Organic Compounds by Reductive Radicals

Matasović, Brunislav; Bonifačić, Marija Dehalogenation of Organic Compounds by Reductive Radicals. In: Znanstveni susreti 3. vrste (7 July 2011 - 8 July 2011) Zagreb, Hrvatska. (Unpublished)

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Abstract

Halogenated aromatic compounds are common toxic pollutants of industrial and communal waters. Usual methods used for their decomposition are radical-based, primarily with hydroxyl radical (·OH). This radical is highly reactive with all agents present in water so overall yields are very low. Therefore, it is interesting to find out other potentially useful radicals for radiolysis of chloro-, bromo-, and iodophenols, halogenated aliphatic compounds and 5-bromouracil. Carbon-centred radicals, ·CH(CH3)OH, ·CH2OH, and ·CO2-, in air-free aqueous solutions in the presence of ethanol, methanol or sodium formate as precursors of reductive organic radicals have been employed. The presence of sodium hydrogen carbonate and ammonium acetate significantly influences reduction power of carbon-centred radicals (except ·CO2-), while presence of stronger base, potassium hydrogen phosphate, does not improve reduction power of those radicals which is otherwise insufficient for reduction. In systems where reduction is operative, dehalogenation has been observed to occur by a chain process. Additionally, complex between base and reductive radical is formed in case of ·CH(CH3)OH and ·CH2OH. Mechanisms of the abovementioned reduction reactions, simple electron transfer mechanism for ·CO2- and proton-coupled electron transfer for ·CH(CH3)OH and ·CH2OH, have been investigated. System with the concentration of NaHCO3 of 10 mmol/dm3 gives the optimal outcome, i.e. the highest yield of halide ions with as low concentration of other components as possible but even better rate constants have been achieved with ·CO2- (for one to two orders of magnitude). Equilibrium constants of complexes observed in this work has been estimated to be almost the same.

Item Type: Unpublished conference/workshop items or lecture materials
Uncontrolled Keywords: Halogenated aromatic compounds
Subjects: NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
Divisions: Division of Physical Chemistry
Depositing User: Marija Bonifačić
Date Deposited: 17 Sep 2012 14:05
Last Modified: 15 Feb 2016 15:37
URI: http://fulir.irb.hr/id/eprint/285

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