Abstract

We present a comprehensive reaction mechanism for the benzyne formation through the 1,2-di-iodobenzene photolysis, a topic of major interest in organic synthesis. Our findings firmly support the experiment-based hypothesis of Kharasch and Sharm [Chem Comm, 1967, 10, 492-493], revealing that C-I bonds break homolytically. Upon photolysis, benzyne and molecular iodine are the ground-state products resulting from a non-adiabatic deactivation, whereas the 2-iodo phenyl radical is produced from the triplet excited state. The confluence of both funnels at the same conical point sharpens the competition, significantly limiting the organic synthesis of specific products. Results further indicate that benzyne forms via a two-step process involving the elimination of both iodine atoms without a radical intermediate.