Paint Solvent to Food Additive: an Environmental Route of Dehalogenation for 4-Chlorobenzotrifluoride
2008
Young, Cora J. | Gómez Biagi, Rodolfo F. | Hurley, Michael D. | Wallington, Timothy J. | Mabury, Scott A.
In an effort to reduce volatile organic compounds (VOCs) in paint solvents, replacements containing non-VOC compounds have been proposed. One such compound is 4-chlorobenzotrifluoride (CBTF), for which environmental fate studies have not been conducted. The objective of the present study was to determine the products of the atmospheric oxidation of CBTF and the aqueous fate of these products. Smog chamber experiments were performed to measure the kinetics and mechanism of atmospheric oxidation. A rate constant of 2.22 (+/-0.30) x 10⁻¹³ cm³ molecule⁻¹ s⁻¹ was determined for the reaction of hydroxyl radicals with CBTF in 700 Torr of air at 296 K. Using offline sampling and gas chromatography coupled to mass spectroscopic analysis, it was determined that 2-chloro-5-trifluoromethylphenol (o-CTFP) was the primary product of CBTF atmospheric oxidation. Aqueous photolysis of o-CTFP in deionized water proceeded at a rate of 1.3 (+/-0.1) x 10⁻⁴ s⁻¹, corresponding to a half-life of 1.5 +/- 0.1 h and a quantum yield of 6.6 (+/-0.4) x 10⁻⁴. The mechanism of photolysis was investigated using liquid chromatography coupled to tandem mass spectrometry, which suggested that degradation of o-CTFP occurred via photonucleophilic displacement of chlorine, followed by photoinduced hydrolysis of the trifluoromethyl group to yield 3,4-dihydroxybenzoic acid (an approved food additive considered to be nontoxic).
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