Abstract
The present investigation theoretically reports the comprehensive kinetic mechanism of the reaction between aniline and the methyl radical over a wide range of temperatures (300-2000 K) and pressures (76-76,000 Torr). The potential energy surface of the C(6)H(5)NH(2) + CH(3) reaction has been established at the CCSD(T)//M06-2X/6-311++G(3df,2p) level of theory. The conventional transition-state theory (TST) was utilized to calculate rate constants for the elementary reaction channels, while the stochastic RRKM-based master equation framework was applied for the T- and P-dependent rate-coefficient calculation of multiwell reaction paths. Hindered internal rotation and Eckart tunneling treatments were included. The H-abstraction from the -NH(2) group of aniline (to form P1 (C(6)H(5)NH + CH(4))) has been found to compete with the CH(3)-addition on the C atom at the ortho site of aniline (to form IS2) with the atmospheric rate expressions (in cm(3) molecule(-1) s(-1)) as k(a1) = 7.5 × 10(-23) T(3.04) exp[(-40.63 ± 0.29 kJ·mol(-1))/RT] and k(b2) = 2.29 × 10(-3) T(-3.19) exp[(-56.94 ± 1.17 kJ·mol(-1))/RT] for T = 300-2000 K and P = 760 Torr. Even though rate constants of several reaction channels decrease with increasing pressures, the total rate constant k(total) = 7.71 × 10(-17) T(1.20) exp[(-40.96 ± 2.18 kJ·mol(-1))/RT] of the title reaction still increases as the pressure increases in the range of 76-76,000 Torr. The calculated enthalpy changes for some species are in good agreement with the available experimental data within their uncertainties (the maximum deviation between theory and experiment is ∼11 kJ·mol(-1)). The T1 diagnostic and spin contamination analysis for all species involved have also been observed. This work provides sound quality rate coefficients for the title reaction, which will be valuable for the development of detailed combustion reaction mechanisms for hydrocarbon fuels.