Benchmark potential energy surface mapping of the F + CHNH reaction.

This electronic structure study reveals four exothermic and two endothermic reaction pathways of the F + CHNH system: the barrierless hydrogen abstraction from the methyl/amino group (HF + CHNH/CHNH), amino/methyl substitution (NH + CHF and CH + NHF) and hydrogen substitution from the two functional groups (H + CHFNH/CHNHF). The benchmark classical and adiabatic energies are obtained using a high-accuracy composite approach, where the gold-standard explicitly-correlated coupled cluster method (CCSD(T)-F12b) is applied with the correlation-consistent polarized valence quintuple-zeta F12 basis set (cc-pV5Z-F12) and further additive energy contributions. Considering indispensable post-(T) correlation, core correlation, scalar relativistic, spin-orbit and harmonic zero-point energy corrections, the obtained global minimum of the potential energy surface is the post-reaction CHNH⋯HF complex in the product channel. Although each substitution pathway has a high barrier, the energies of amino-substitution and methyl-hydrogen-substitution products are below the energy of the reactants, as well as the submerged-barrier hydrogen-abstraction pathways.