Textbook Question
Only after working Assessment 22.53, predict the product of the following reactions.
(a)
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16. Conjugated Systems
Claisen Rearrangement
Multiple Choice
In the Claisen rearrangement of allyl phenyl ether, what is the major organic product formed?
A
(phenol)
B
o-allylphenol
C
p-allylphenol
D
benzyl alcohol
Verified step by step guidance1
Step 1: Understand the Claisen rearrangement mechanism, which is a [3,3]-sigmatropic rearrangement involving allyl aryl ethers. The reaction proceeds through a cyclic six-membered transition state, leading to the migration of the allyl group to the ortho or para position relative to the oxygen atom on the aromatic ring.
Step 2: Identify the starting material, allyl phenyl ether, which consists of a phenyl ring bonded to an oxygen atom that is also connected to an allyl group (–CH2–CH=CH2).
Step 3: Recognize that the Claisen rearrangement typically favors formation of the ortho-substituted product due to the proximity of the allyl group to the ortho position, allowing the cyclic transition state to form more easily and with less steric hindrance.
Step 4: Draw the product structures for both ortho-allylphenol and para-allylphenol to compare. The ortho product has the allyl group adjacent to the hydroxyl group on the benzene ring, while the para product has it opposite the hydroxyl group.
Step 5: Conclude that the major product is o-allylphenol (ortho-allylphenol) because the Claisen rearrangement proceeds through a six-membered cyclic transition state that favors substitution at the ortho position relative to the phenol oxygen.
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