Unexpected hydrodefluorination of 3-Cl-tetrafluoropyridine. Interpretation through analysis of the potential energy surface for its radical anion

• Published in: Journal of fluorine chemistry 2020-06, Vol.234, p.109513, Article 109513
• Main Authors: Andreev, Rodion V., Beregovaya, Irina V., Shchegoleva, Lyudmila N.
• Format: Article
• Language: English
• Subjects: Anions; Chemical analysis; Dehalogenation; Intermediate radical anions; Mixed fluoro-chloro-pyridines; Polarity; Potential energy; Potential energy surface sections; Quantum chemistry; Reaction mechanism; Reductive dehalogenation; Solvent reorganization; Solvents
• ISSN: 0022-1139; 1873-3328
• DOI: 10.1016/j.jfluchem.2020.109513

[Display omitted] •3-chloro-tetrafluoropyridine radical anion decay was investigated theoretically.•Solvation effects are capable to affect the dehalogenation channel ratio.•What C-Hal bond will be broken depends on its position in pyridine ring.•The energy preference of Cl− elimination vs. the low barrier for F− elimination.•3-chloro-tetrafluoropyridine hydrodehalogenation - thermodynamics vs. kinetics. The mechanism of the reductive dehalogenation of 3-chloro-2,4,5,6-tetrafluoropyridine has been considered in terms of quantum-chemical analysis of the potential energy surface (PES) for its daughter radical anion (RA). We analyzed PES sections along the coordinates of the RA fragmentation through the loss of a halide ion. Based on DFT calculations, a model has been built that included the solvent reorganization during the RA decomposition. The model enabled us to describe the change of the RA decay channel with an increase in solvent polarity which was found by V.P. Krasnov and V.E. Platonov, 2000. The change is due to a difference in the fine mechanisms of C-F and C-Cl bond cleavage.