Q19 · CSIR-NET Chemistry, December 2013
Paper: CSIR-NET December 2013 · Subject: Organic Chemistry · Chapter: Pericyclic Reactions · Topic: Sigmatropic Shifts · Marks: 2 · Difficulty: Medium
The following reaction proceeds through a 
$\Delta$ 
$\Delta$ (a)1, 3-sigmatropic rearrangement
(b)2, 3-sigmatropic rearrangement
(c)3, 3-sigmatropic rearrangement
(d)3, 5-sigmatropic rearrangement
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
An allyl vinyl ether heated gives a [3,3]-sigmatropic (Claisen) rearrangement: the O–C bond of the ring breaks and a new C–C bond forms, delivering the γ,δ-unsaturated aldehyde shown.
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