Textbook Question
Show what product would result from the [6 + 2] cycloaddition of hexa-1,3,5-triene with maleic anhydride.
16. Conjugated Systems
Photochemical Cycloaddition Reactions
Struggling with Organic Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
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
Verified step by step guidance1
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.
9:36mWatch next
Master MO Theory of Photochemical Cycloadditions with a bite sized video explanation from Johnny
Start learningRelated Videos
Related Practice
Photochemical Cycloaddition Reactions practice set
Problem sets built by lead tutorsExpert video explanations