Q83 · CSIR-NET Chemistry, December 2014
Paper: CSIR-NET December 2014 · Subject: Organic Chemistry · Chapter: Photochemical Reactions · Topic: Photocycloaddition · Marks: 2 · Difficulty: Medium
The cyclic product(s) of the following photochemical reaction is(are) 
(a)only cis-1, 2-dimethylcyclopentane
(b)only trans-1, 2-dimethylcyclopentane
(c)a mixture of cis- and trans-1, 2-dimethylcyclopentanes
(d)only 2, 6-dimethylcyclohexanol
Answer
Answer: C ✓ checked by 4AB · confidence medium
Explanation
In the vapour phase, Norrish type I α-cleavage and loss of CO give a 1,5-biradical. It closes without stereocontrol, giving both cis- and trans-1,2-dimethylcyclopentane (c).
Study loop for Photochemical Reactions