Dash M.RMuthiah BMishra S.SAnnaraj BKING-CHUEN LIN2022-04-252022-04-2520211432881Xhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85114299202&doi=10.1007%2fs00214-021-02833-x&partnerID=40&md5=f64d23440cf3cd7b7e55d5c637a021e9https://scholars.lib.ntu.edu.tw/handle/123456789/606906The rate constants of ethynyl (C2H) radical reaction with isobutane (kiso) and neopentane (kneo) were calculated for the first time using canonical variational transition state theory (CVT) with small-curvature tunneling (SCT) in the temperature range of 150–5000?K. The geometries and frequencies of all the stationary points were calculated at the M06-2X/Aug-cc-pVTZ level of theory. Thermodynamics (ΔH°298 and ΔG°298) results govern that the title reactions are highly exothermic and spontaneous in nature. The rate constants obtained over the temperature range of 150–300?K were used to derive the modified Arrhenius expressions: kiso = 6.84 × 10–19 T2.5 exp[1496/T] and kneo = 1.72 × 10–17 T2.0 exp[938/T] cm3 molecule?1?s?1. Branching ratio calculation for the reaction of C2H radical with isobutane shows that the tertiary-H abstraction channel is dominant (> 95%) over the complete temperature range. ? 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Ethynyl radicalsM06-2XPotential energy surfaceRate constantsTransition statejournal article10.1007/s00214-021-02833-x2-s2.0-85114299202