Theoretical Kinetic and Mechanistic Studies on the Reactions of CF(3)CBrCH(2) (2-BTP) with OH and H Radicals

CF(3)CBrCH(2) (2-bromo-3,3,3-trifluoropropene, 2-BTP) is a potential replacement for CF(3)Br; 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)=CH(2) 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 (CF(3)CBrCH(2)OH) is the dominant channel at low temperatures, while the substitution reaction (CF(3)COHCH(2) + Br) and H abstraction reaction (CF(3)CBrCH + H(2)O) dominates at high temperatures and elevated pressures. For 2-BTP + H, the addition to the initial adduct (CF(3)CBrCH(3)) also dominates the overall kinetics at low temperatures, while Br abstraction reaction (CF(3)CCH(2) + HBr) and β-scission of the adduct forming CF(3)CHCH(2) + 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.