Q52E

Question

The major product formed by intramolecular aldol cyclization of 2,5-heptanedione (Problem 23-51) has two singlet absorptions in the 1H NMR spectrum, at 1.65 d and 1.90 d, and has no absorptions in the range 3 to 10 d. What is its structure?

Step-by-Step Solution

Verified
Answer

One of the two enone products having two methyl groups within the ring has two singlet absorptions in the 1H NMR spectrum, at 1.65 d and 1.90 d, and has no absorptions in the range 3 to 10 d.

1Formation of the product by intramolecular aldol cyclization of 2,5-heptanedione:

2Explanation of structure

Since product [A] have two methyl group and no vinylic hydrogen which give two singlet absorptions in the 1H NMR spectrum, at 1.65 d and 1.90 d, and has no absorptions in the range 3 to 10 d.