Q25 · CSIR-NET Chemistry, June 2011

Paper: CSIR-NET June 2011 · Subject: Organic Chemistry · Chapter: Photochemical Reactions · Topic: Photocycloaddition · Marks: 2 · Difficulty: Medium

The concerted photochemical reaction between two olefins leading to a cyclobutane ring is:
(a)$\pi 2_s + \pi 2_a$ cycloaddition
(b)$\pi 2_s + \pi 2_s$ cycloaddition
(c)$\sigma 2_s + \sigma 2_s$ cycloaddition
(d)$\pi 2 \mathrm{s}+\sigma 2 \mathrm{a}$ cycloaddition
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
A photochemical [2+2] cycloaddition is suprafacial on both components, [π2s + π2s]: the excited-state HOMO of one alkene matches the LUMO of the other in phase.

Study loop for Photochemical Reactions

1. Practise the PYQsPrevious-year questions, with answers

· Browse this chapter in the app