Isotope Fractionation Associated with the Photochemical Dechlorination of Chloroanilines

Marco Ratti, Silvio Canonica, Kristopher McNeill, Jakov Bolotin, Thomas B. Hofstetter

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Isotope fractionation associated with the photochemical transformation of organic contaminants is not well understood and can arise not only from bond cleavage reactions but also from photophysical processes. In this work, we investigated the photolytic dechlorination of 2-Cl- and 3-Cl-aniline to aminophenols to obtain insights into the impact of the substituent position on the apparent 13C and 15N kinetic isotope effects (AKIEs). Laboratory experiments were performed in aerated aqueous solutions at an irradiation wavelength of 254 nm over the pH range 2.0 to 7.0 in the absence and presence of Cs+ used as an excited singlet state quencher. Photolysis of 2-Cl-anilinium cations exhibits normal C and inverse N isotope fractionation, while neutral 2-Cl-aniline species shows inverse C and normal N isotope fractionation. In contrast, the photolysis of 3-Cl-aniline was almost insensitive to C isotope composition and the moderate N isotope fractionation points to rate-limiting photophysical processes. 13C- and 15N-AKIE-values of 2-Cl-aniline decreased in the presence of Cs+, whereas those for 3-Cl-aniline were not systematically affected by Cs+. Our current and previous work illustrates that photolytic dechlorinations of 2-Cl-, 3-Cl-, and 4-Cl-aniline isomers are each accompanied by distinctly different and highly variable C and N isotope fractionation due to spin selective isotope effects.

Original languageEnglish (US)
Pages (from-to)9797-9806
Number of pages10
JournalEnvironmental Science and Technology
Volume49
Issue number16
DOIs
StatePublished - Jul 21 2015

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