Origin of the Regioselectivity in the Gas‐Phase Aniline+CH 3 + Electrophilic Aromatic Substitution

Nonadiabatic ab initio molecular dynamics simulations are carried out to monitor the attack of CH 3 + on aniline in the gas phase to form the corresponding σ complexes. The reaction is ultrafast and is governed by a single electron transfer within 30 fs, which involves two sequential conical intersections and finally produces a radical pair. Positive‐charge allocation in the aromatic compound is found to govern the substitution pattern in ortho , meta , or para position. Although the major products in the first step of the electrophilic aromatic substitution are the ortho and para σ complexes, initially 26 % of the simulated trajectories also form meta complexes, which then undergo H shifts, mainly to the para position.