Chemical Reactions and Mechanisms

Quantum tunneling allows atoms and molecules to pass through energy barriers that classical physics would forbid them to cross, and in certain chemical reactions this effect is not just a minor correction but the dominant factor determining which products form—a phenomenon called tunneling control. Research in this area focuses especially on reactive intermediates such as carbenes and nitrenes, short-lived species whose rearrangements and bond-forming steps can be steered almost entirely by tunneling, even for relatively heavy atoms like carbon and nitrogen. Experiments using matrix isolation—trapping reactive species at cryogenic temperatures in an inert solid—combined with high-level computational modeling have made it possible to observe and predict these effects with growing precision. Open questions include understanding exactly when and why tunneling overrides conventional thermal reactivity, how to exploit that selectivity deliberately in organic synthesis, and whether heavy-atom tunneling is more widespread across chemistry than currently recognized.

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43,870

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285,231

Keywords

Tunneling ControlChemical ReactionsNitrenesCarbenesPhotochemistryOrganic Synthesis