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Formation of chlorinated breakdown products during degradation of sunscreen agent, 2-ethylhexyl-4-methoxycinnamate in the presence of sodium hypochlorite
Environmental Science and Pollution Research (2016)
  • Alicja Gackowska, University of Technology and Life Sciences in Bydgoszcz
  • Maciej Przybyłek, Nicolaus Copernicus University of Torun
  • Waldemar Studziński, University of Technology and Life Sciences in Bydgoszcz
  • Jerzy Gaca, University of Technology and Life Sciences in Bydgoszcz
Abstract
In this study, a new degradation path of sunscreen active ingredient, 2-ethylhexyl-4-methoxycinnamate (EHMC) and 4-methoxycinnamic acid (MCA) in the presence of sodium hypochlorite (NaOCl), was discussed. The reaction products were detected using gas chromatography–mass spectrometry (GC-MS). Since HOCl treatment leads to more polar products than EHMC, application of polar extracting agents, dichloromethane and ethyl acetate/n-hexane mixture, gave better results in terms of chlorinated breakdown products identification than n-hexane. Reaction of EHMC with HOCl lead to the formation of C=C bridge cleavage products such as 2-ethylhexyl chloroacetate, 1-chloro-4-methoxybenzene, 1,3-dichloro-2-methoxybenzene, and 3-chloro-4-methoxybenzaldehyde. High reactivity of C=C bond attached to benzene ring is also characteristic for MCA, since it can be converted in the presence of HOCl to 2,4-dichlorophenole, 2,6-dichloro-1,4-benzoquinone, 1,3-dichloro-2-methoxybenzene, 1,2,4-trichloro-3-methoxybenzene, 2,4,6-trichlorophenole, and 3,5-dichloro-2-hydroxyacetophenone. Surprisingly, in case of EHMC/HOCl/UV, much less breakdown products were formed compared to non-UV radiation treatment. In order to describe the nature of EHMC and MCA degradation, local reactivity analysis based on the density functional theory (DFT) was performed. Fukui function values showed that electrophilic attack of HOCl to the C=C bridge in EHMC and MCA is highly favorable (even more preferable than phenyl ring chlorination). This suggests that HOCl electrophilic addition is probably the initial step of EHMC degradation.
Keywords
  • 2-Ethylhexyl-4-methoxycinnamate,
  • Octyl methoxycinnamate,
  • Emerging pollutants,
  • Chlorination,
  • Sunscreen,
  • Halogenated disinfection byproducts,
  • GC-MS,
  • Local reactivity,
  • Fukui function
Publication Date
2016
DOI
10.1007/s11356-015-5444-0
Citation Information
Alicja Gackowska, Maciej Przybyłek, Waldemar Studziński and Jerzy Gaca. "Formation of chlorinated breakdown products during degradation of sunscreen agent, 2-ethylhexyl-4-methoxycinnamate in the presence of sodium hypochlorite" Environmental Science and Pollution Research Vol. 23 Iss. 2 (2016) p. 1886 - 1897
Available at: http://works.bepress.com/maciej-przybyek/15/