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

Abstract

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.

Chemical mechanism and atmospheric degradation of C4F9N initiated by OH radical: Ab initio kinetic exploration

“…Moreover, compared to CC β‐scissions, these two pathways are obviously unfavorable by breaking the stronger CF bonds. This phenomenon is in accordance with the former finding for CF 3 CBrCH 2 + OH system [23].…”

“…They proceed with TS3 to TS6 with 69.45–81.11 kcal/mol barrier heights to yield FOH, as listed in Table 1. This phenomenon is mainly caused by the combined effect of the weak interaction between OH and F and the high bonding strength of CF [23]. Consequently, all the abstractions and substitutions are exothermic reactions.…”

Thermal Decomposition Mechanism and Fire-Extinguishing Performance of trans-1,1,1,4,4,4-Hexafluoro-2-butene: A Potential Candidate for Halon Substitutes

“…Nevertheless, the Europe Union is requested to accomplish the replacement of Halon 1301 and 1211 in newly constructed aircrafts by 2018 and in existing ones by 2040. Because of the urgency and necessity of Halon replacement, a worldwide effort has been made to search for environmentally safer fire extinguishant in the past decades. , …”

“…Because of the urgency and necessity of Halon replacement, a worldwide effort has been made to search for environmentally safer fire extinguishant in the past decades. 2,3 Among the numerous candidates for Halon substitutes, the products of hydrofluorocarbons (HFCs), 2-bromo-3,3,3trifluoropropane (2-BTP), and perfluoro-2-methyl-3-pentanone (PFMP) have been well studied and were found to be promising agents for clean fire suppression. For instance, 1,1,1,2,3,3,3-heptafluoropane (HFC-227ea) is an effective agent for suppression of class A fires, 4 and a mixture of HFC-227ea with NaHCO 3 could be used for fire extinguishment in the occupied spaces such as crew compartment.…”