교과서 질문
Show what product would result from the [6 + 2] cycloaddition of hexa-1,3,5-triene with maleic anhydride.
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16. Conjugated Systems
Photochemical Cycloaddition Reactions
객관식
Use FMOT to predict the mechanism and products for the following cycloaddition. If no product is favored, write “symmetry-disallowed” in place of the product.
A
Symmetry-disallowed
B
C
D
검증된 단계별 안내1
Identify the type of cycloaddition reaction: The problem involves a 2π + 2π cycloaddition, specifically the dimerization of thymine, which is a photochemical reaction.
Understand the Frontier Molecular Orbital Theory (FMOT): In photochemical reactions, the excited state of the molecules is considered. The HOMO of one molecule interacts with the LUMO of the other.
Analyze the symmetry of the molecular orbitals: For a 2π + 2π cycloaddition to be symmetry-allowed, the interacting orbitals must have compatible symmetries in their excited states.
Evaluate the symmetry of the thymine dimerization: In the excited state, the symmetry of the π orbitals allows the reaction to proceed, making it symmetry-allowed under photochemical conditions.
Predict the product: The reaction leads to the formation of a cyclobutane ring between the two thymine molecules, resulting in a thymine dimer, as shown in the provided images.
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