# Photochemical rearrangement of 4,4‐diphenylcyclohexa‐2,5‐dien‐1‐one Tags: organic-chemistry, carbonyl-compounds, rearrangements - Score: 9 - Views: 1224 - Answers: 2 - Answered: yes - Asked by: booma vijay (877 rep) - Asked: 2020-05-10 - Edited: 2020-05-10 - Site: chemistry ## Question I can see how the option A and B are correct as it is just a standard dienone–phenol type reaction which involves a phenyl shift. However, the given answer is A, B, C and D. I do not see how C and D are formed. Does the presence of light affect the reaction? If so, how? ## Answers ### Answer by user55119 (score: 8 [ACCEPTED]) The formation of structure 6 (your D) occurs as follows. Photolysis of dienone 1 affords excited state 2 that forms cyclopropane 3. In turn, 3 is capable of breaking a different cyclopropane bond to form 5-membered ring 4. Structure 5 is a resonance structure of 4. Structure 5 closes to the [3.1.0] product 6 (your D). I don't know how you formed A (12 here) but further photolysis of 6 can form 12 via a bridged phenyl migration as shown in structure 9. A similar migration in structure 2 leads to your B. Of course, structure C has only five carbons and was added to th