Barrierless Reactions of Three Benzonitrile Radical Cations with Ethylene

Abstract

Reactions of three protonated benzonitrile radical cations with ethylene are investigated. Product branching ratios and reaction kinetics, measured using ion-trap mass spectrometry, are reported and mechanisms are developed with support from quantum chemical calculations. Reactions proceed via pre-reactive van der Waals complexes with no energy barrier (above the reactant energy) and form radical addition and addition–elimination product ions. Rate coefficients are 4-dehydrobenzonitrilium: 1.72 ± 0.01 × 10−11 cm3 molecule−1 s−1, 3-dehydrobenzonitrilium: 1.85 ± 0.01 × 10−11 cm3 molecule−1 s−1, and 2-dehydrobenzonitrilium: 5.96 ± 0.06 × 10−11 cm3 molecule−1 s−1 (with ±50 % absolute uncertainty..