Textbook Question
Show that the [4 + 4] cycloaddition of two butadiene molecules to give cycloocta-1,5-diene is thermally forbidden but photochemically allowed.
16. Conjugated Systems
Pericyclic Reaction
Struggling with Organic Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Identify the type of following pericyclic reaction.
A
Cycloadditions
B
Electrocyclic
C
Sigmatropic shift
Verified step by step guidance1
Examine the chemical structures provided in the image. The left structure is a bicyclic compound, and the right structure is a different bicyclic compound. The reaction involves a change in the connectivity of atoms within the bicyclic framework.
Note the presence of 'hv' above the reaction arrow, indicating that this reaction is photochemically driven. This is a key detail that can help identify the type of pericyclic reaction.
Understand the types of pericyclic reactions: Cycloadditions involve the formation of a cyclic product from acyclic precursors, electrocyclic reactions involve the opening or closing of a ring, and sigmatropic shifts involve the migration of a sigma bond across a pi system.
Consider the transformation shown: The reaction involves a change in the connectivity of the bicyclic structure without the addition of new atoms or the formation of a new ring. This suggests a rearrangement within the existing framework.
Based on the structural change and the photochemical condition, identify the reaction as an electrocyclic reaction, which involves the opening or closing of a ring system under thermal or photochemical conditions.
7:37mWatch next
Master Properties and Types of Pericyclic Reactions with a bite sized video explanation from Johnny
Start learningRelated Videos
Related Practice
Pericyclic Reaction practice set
Problem sets built by lead tutorsExpert video explanations