Fragmentation reactions of phenoxide anions: deprotonated Dinoterb and related structures |
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Authors: | Rifai Ahmad Bourcier Sophie Arquier Delphine Charvet Yannick Jaber Farouk Bouchoux Guy |
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Institution: | Laboratoire des Mécanismes Réactionnels, Ecole Polytechnique, CNRS, 91128, Palaiseau, France. |
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Abstract: | Dinoterb (6-t-butyl-2,4-dinitrophenol), 1, Dinoseb (6-secbutyl-2,4-dinitrophenol), 2, TBP (2-t-butylphenol), 3, and DNP (2,4-dinitrophenol), 4, have been analyzed by electrospray ionization in the negative mode (ESI-N) - tandem mass spectrometry. Nominal laboratory collision energy was varied from zero to 60 eV during the experiments. Apparent fragmentation energies were estimated from a parametric fitting of the collision efficiency curves. In parallel, fragmentation mechanisms of the deprotonated molecules M-H](-) were explored using quantum chemistry modeling at the B3LYP/6-31 + G(d,p) level. A major fragmentation of the M-H](-) ions of Dinoterb and Dinoseb is elimination of an alcohol molecule. This reaction is shown to involve one oxygen atom originating from a nitro group rather than the phenoxide moiety. Eliminations of NO, C(4) and CH(2) = C(CH(3))(2), i.e. reactions involving significant rearrangements, constitute the major part of the other fragmentation pathways observed from 3-H](-) and 4-H](-) ions. |
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Keywords: | herbicides tandem mass spectrometry negative ions ESI DFT quantum chemistry computations fragmentation mechanisms |
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