Maiara Passos

and 3 more

Thermal rate coefficients for the hydrogen abstraction reactions of 3-butenal by hydrogen atom were obtained, for the first time, with the application of the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT). Torsional anharmonicity due to the hindered rotors was taken into account with the calculation of the rovibrational partition function using the extended two-dimensional torsional method (E2DT). In contrast with the (E)-2-butenal reactions, the abstraction reactions of 3-butenal proceed via five reaction channels, (R1)–(R5). In the conformational search, 48 distinguishable structures of transition states were found, including enantiomers, and separated into six conformational reaction channels (CRC). The individual reactive paths were constructed, variational and recrossing coefficients estimated, and the multipath rate constants obtained. The torsional anharmonicity is responsible for increased the rate constants for (R2). In the case of (R1), (R3), (R4), and (R5), this effect decreased the velocity of reactions. Compared to the overall (E)-2-butenal + H reaction, the thermal rate constants of this study are faster in a wide range of temperatures. The analysis of the contributions of each conformer of the transition state shows an important contribution of the high energy rotamers in the total flux of (R1)–(R5). After fitting of rate constants in a four-parameters equation, the activation energy estimation shown strong temperature dependence.