Q68 · CSIR-NET Chemistry, June 2013
Paper: CSIR-NET June 2013 · Subject: Organic Chemistry · Chapter: Pericyclic Reactions · Topic: Woodward Hoffmann Rules · Marks: 2 · Difficulty: Medium
The most appropriate mode of cyclisation in the following transformation is 
(a)con-rotatory in photochemical; and dis-rotatory in thermal conditions.
(b)con-rotatory in thermal; and dis-rotatory in photochemical conditions.
(c)con-rotatory in thermal; and con-rotatory in photochemical conditions.
(d)dis-rotatory in photochemical; and dis-rotatory in thermal conditions.
Answer
Answer: A ✓ checked by 4AB · confidence medium
The source book printed D; on checking, A is correct — see the explanation.
Explanation
A 6π (4n + 2) electrocyclisation is disrotatory under thermal and conrotatory under photochemical conditions.
Study loop for Pericyclic Reactions