Mechanistic and Kinetic Study of CF₃CH═CH₂+ OH Reaction

Abstract

The potential energy surfaces of the CF(3)CH═CH(2) + OH reaction have been investigated at the BMC-CCSD level based on the geometric parameters optimized at the MP2/6-311++G(d,p) level. Various possible H (or F)-abstraction and addition/elimination pathways are considered. Temperature- and pressure-dependent rate constants have been determined using Rice-Ramsperger-Kassel-Marcus theory with tunneling correction. It is shown that IM1 (CF(3)CHCH(2)OH) and IM2 (CF(3)CHOHCH(2)) formed by collisional stabilization are major products at 100 Torr pressure of Ar and in the temperature range of T < 700 K (at P = 700 Torr with N(2) as bath gas, T ≤ 900 K), whereas CH(2)═CHOH and CF(3) produced by the addition/elimination pathway are the dominant end products at 700-2000 K. The production of CF(3)CHCH and CF(3)CCH(2) produced by hydrogen abstractions become important at T ≥ 2000 K. The calculated results are in good agreement with available experimental data. The present theoretical study is helpful for the understanding the characteristics of the reaction of CF(3)CH═CH(2) + OH.

Hydroxyl radical reaction rate coefficients as a function of temperature and IR absorption cross sections for CF3CH=CH2 (HFO-1243zf), potential replacement of CF3CH2F (HFC-134a)

“…Thomsen and Jorgensen (2009) reported that computed k OH (298 K) for the addition reaction of OH radical with CF 3 CH=CH 2 using DFT, MP2, and CCSD(T) methods was in good agreement with experimental values at 298 K. Recently, Zhang et al (2012) have predicted by multichannel RRKM and transition state theory calculations that k OH (298 K) for reaction 1 was independent of a total pressure between 10 and 10 10 Torr (of Ar and N 2 ). However, the temperature dependence of k OH in Ar between 252 and 370 K experimentally observed by Orkin et al (1997) was not theoretically reproduced by Zhang et al (2012). More recently, Balaganesh and Rajakumar (2014) performed calculations on k OH for reaction 1 at the MP2 and BMC-CCSD levels of theory in the temperature range of 200-3,000 K in accordance with the T dependence reported by Orkin et al (1997).…”

“…From the theoretical point of view, reaction 1 has been recently investigated using different theoretical methods (Thomsen and Jørgensen 2009;Zhang et al 2012;Balaganesh and Rajakumar 2014). Thomsen and Jorgensen (2009) reported that computed k OH (298 K) for the addition reaction of OH radical with CF 3 CH=CH 2 using DFT, MP2, and CCSD(T) methods was in good agreement with experimental values at 298 K. Recently, Zhang et al (2012) have predicted by multichannel RRKM and transition state theory calculations that k OH (298 K) for reaction 1 was independent of a total pressure between 10 and 10 10 Torr (of Ar and N 2 ).…”

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

“…For the average energy transferred per collision, <ΔE down >, there is no experimental date available for the target systems in the present work. Vahid et al [37] used a value of 129 cm −1 for CF 3 CF=CF 2 reacting with OH, and Zhang et al [38] used a value of 200 cm −1 in N 2 and 100 cm −1 in Ar for the reactions of CF 3 CH=CH 2 with OH. Considering a heavy Br atom in 2-BTP, we used a temperature-dependent form for this value, that is, <ΔE down > = ΔE 0 (T/300) n (ΔE 0 = 200, n = 0.85).…”

Theoretical Kinetics Studies on the Reaction of CF3CF═CF2 with Hydroxyl Radical

“…In the present research, by applying steady-state approximation to the activated intermediates and carrying out statistical mechanics manipulations similar to those of Hou et al, expressions for the rate constants of individual channels are derived. Recently, a similar procedure was used by Zhang et al 30 in the theoretical study of the kinetics and mechanism of the CF 3 CHCH 2 + OH reaction. These expressions are discussed in the next sections.…”