Q82 · CSIR-NET Chemistry, December 2013
Paper: CSIR-NET December 2013 · Subject: Organic Chemistry · Chapter: Pericyclic Reactions · Topic: Pericyclic Reactions – General · Marks: 2 · Difficulty: Medium
The conditions A-B, required for the following pericyclic reactions are 
(a)$\mathrm{A}-\Delta$; $\mathrm{B}-\Delta$
(b)$\mathrm{A}-\mathrm{hv}$; $\mathrm{B}-\Delta$
(c)A - hv; B- hv
(d)$\mathrm{A}-\Delta$; $\mathrm{B}-\mathrm{h} \nu$
Answer
Answer: A ✓ checked by 4AB · confidence high
The source book printed B; on checking, A is correct — see the explanation.
Explanation
The 8π closure of the octatetraene is thermal conrotatory, setting the Me groups trans. The following 6π closure to the cis-fused bicycle is thermal disrotatory. A = Δ, B = Δ (a).
Study loop for Pericyclic Reactions