Theoretical Kinetic and Mechanistic Studies on the Reactions of CF₃CBrCH₂ (2-BTP) with OH and H Radicals

• Published in: Molecules (Basel, Switzerland) Vol. 22; no. 12; p. 2140
• Main Authors: Bian, Huiting, Ye, Lili, Sun, Jinhua
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 06-12-2017; MDPI
• Subjects: Ab initio calculation; addition; Alkenes - chemistry; C3H2F3Br; Chemistry; Cleavage; Combustion; Combustion chemistry; Decomposition; elimination; Free radicals; halon replacement; High temperature; Hydrogen - chemistry; Hydroxyl Radical - chemistry; Inhibition; Kinetics; Laboratories; Low temperature; Models, Chemical; Models, Molecular; Models, Theoretical; Potential energy; Radicals; rate coefficients; Reaction kinetics; Substitution reactions; rate coefficients; Ab initio calculation; C3H2F3Br; elimination; halon replacement; addition
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules22122140

CF₃CBrCH₂ (2-bromo-3,3,3-trifluoropropene, 2-BTP) is a potential replacement for CF₃Br; however, it shows conflicted inhibition and enhancement behaviors under different combustion conditions. To better understand the combustion chemistry of 2-BTP, a theoretical study has been performed on its reactions with OH and H radicals. Potential energy surfaces were exhaustively explored by using B3LYP/aug-cc-pVTZ for geometry optimizations and CCSD(T)/aug-cc-pVTZ for high level single point energy refinements. Detailed kinetics of the major pathways were predicted by using RRKM/master-equation methodology. The present predictions imply that the -C(Br)=CH₂ moiety of 2-BTP is most likely to be responsible for its fuel-like property. For 2-BTP + OH, the addition to the initial adduct (CF₃CBrCH₂OH) is the dominant channel at low temperatures, while the substitution reaction (CF₃COHCH₂ + Br) and H abstraction reaction (CF₃CBrCH + H₂O) dominates at high temperatures and elevated pressures. For 2-BTP + H, the addition to the initial adduct (CF₃CBrCH₃) also dominates the overall kinetics at low temperatures, while Br abstraction reaction (CF₃CCH₂ + HBr) and β-scission of the adduct forming CF₃CHCH₂ + Br dominates at high temperatures and elevated pressures. Compared to 2-BTP + OH, the 2-BTP + H reaction tends to have a larger effect on flame suppression, given the fact that it produces more inhibition species.