title: Photochemical transformation of ibuprofen into harmful 4-isobutylacetophenone: pathways, kinetics, and significance for surface waters.
abstract: The harmful compound 4-isobutylacetophenone (IBAP) can be formed photochemically from the anti-inflammatory drug ibuprofen (IBP), upon direct photolysis (yield 25 ± 7%, μ ± σ), reaction with ·OH (yield 2.3 ± 0.1%) and reaction with triplet states of chromophoric dissolved organic matter, (3)CDOM* (yield 31 ± 4%). In the latter case, anthraquinone-2-sulphonate was used as CDOM proxy. The three processes would account for most of the photochemical transformation of IBP and IBAP in surface waters. IBAP formation from IBP involves the propanoic acid chain, which is more reactive than the aromatic ring as shown by quantum mechanical calculations. IBAP is expected to undergo slightly faster photochemical transformation than IBP in surface waters, with a modelled pseudo-first order rate constant that is higher by 1.5-1.9 times compared to IBP. Due to fairly high formation yields and depending on IBP emission scenarios, photochemical modelling suggests that IBAP could reach concentration values up to ~15% of IBP in surface waters, thus being a potentially important transformation intermediate. This issue prompts for the need of field studies that provide information on IBAP environmental occurrence, which is virtually unknown at the present moment.
authors: Università degli Studi di Torino, Dipartimento di Chimica, Via Pietro Giuria 5-7, 10125 Torino, Italy.
authors: Giulia
authors: G
authors: Ruggeri
authors: Giovanni
authors: G
authors: Ghigo
authors: Valter
authors: V
authors: Maurino
authors: Claudio
authors: C
authors: Minero
authors: Davide
authors: D
authors: Vione
mesh_terms: D000098:Acetophenones / Q000737:chemistry*; D007052:Ibuprofen / Q000737:chemistry*; D007700:Kinetics; D055668:Photochemical Processes; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000098:Acetophenones; D014874:Water Pollutants, Chemical; C524006:4-isobutylacetophenone; D007052:Ibuprofen
keywords: Non-steroidal anti-inflammatory drugs; Photosensitised transformation; Radical reactions; Surface-water photochemistry; Transformation by-products and intermediates