A theoretical study on mechanism and kinetics of the C2H3 + C2H3 recombination and the isomerization and dissociation of butadiene

[Display omitted] Kinetics and mechanism of the C2H3 + C2H3 recombination and the related isomerization–decomposition of C4H6 have been performed utilizing the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory together with statistical theoretical VRC-TST and RRKM master equation calculations. The potential energy surface describing the C2H3 + C2H3 reaction was established in detail. The evaluated total high-pressure-limit (HPL) rate constant for the entrance C2H3 + C2H3 → 1,3-butadiene reaction, 0.169 × 10−10T−0.508 cm3/molecule/s, agrees closely within 0.1 to ~ 2% with the experimental data given by Kawano and co-workers, 0.163 × 10−10T−0.5 cm3/molecule/s, and the HPL rate constant of the CH2CCH + CH3 → C4H6 reaction can be represented by the expression of 8.51 × 10−11 exp(165.87 cal.mol−1/RT) cm3/molecule/s, in good agreement with the expression of 6.8 × 10−11 exp(258.3 cal.mol−1/RT) cm3/molecule/s given by Knyazev and Slagleare, while the HPL rate constants for C4H6 → C4H5 + H presented by the Arrhenius expressions ka = 0.165 × 1015 exp(-84 kcal mol−1/RT), kb = 0.62 × 1015 exp(-85.8 kcal.mol−1/RT), kc = 0.62 × 1015 exp(−90.2 kcal.mol−1/RT), and kd = 0.2 × 1016 exp(−99.1 kcal.mol−1/RT) s−1, are in reasonable accordance with the expressions reported by Hidaka et al. and Leung and Lindstedt, being ka,expt. = 0.5 × 1015 exp(−87.3 kcal mol−1/RT), kb,expt. = 0.7 × 1015 exp(−86 kcal.mol−1/RT), kc,expt. = 0.42 × 1016 exp(−92.6 kcal.mol−1/RT), and kd,expt. = 0.14 × 1016 exp(−98 kcal.mol−1/RT) s−1, respectively. Bimolecular rate coefficients for 16 channels on the PES were calculated at various pressures from 7.6 to 76000 Torr and 300 ≤ T ≤ 2000 K, which rapidly increase with rising temperatures and slightly decrease with rising pressures. The predicted rate constants and the product yields of the C4H6 dissociation reaction are in reasonably satisfactory agreement with the previous theoretical and experimental data without any adjustment from the quantum-chemical calculations. The recommended temperature-/pressure-dependent rate constants can be confidently utilized for modeling C2H3-related systems under atmospheric and combustion conditions.