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Updated: Jun 24, 2025

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在周周期反应中量子道不稳定性:Cheletropic,Coarctate和Ene的情况

Alexander Frenklach1, Hila Amlani1, Sebastian Kozuch1

  • 1Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel.

Organic letters
|June 7, 2024
PubMed
概括

重原子道,或量子道不稳定性 (QTI),可以在某些反应中引起分子分解. 这项研究表明,由于QTI,逆热,状和状反应中的反应物可能无法检测到.

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Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
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Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
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The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
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