Bicyclo[2.2.1]heptan-2-one completely fails to undergo keto-enol tautomerism despite possessing an acidic -hydrogen. What fundamental structural principle explicitly prevents this tautomerization?

Question

Bicyclo[2.2.1]heptan-2-one completely fails to undergo keto-enol tautomerism despite possessing an acidic $\alpha$ -hydrogen. What fundamental structural principle explicitly prevents this tautomerization?

Prashant Kotian · Accepted Answer

Correct answer: B. Tautomerization to an enol requires the formation of a carbon-carbon double bond at the -position. In rigid bicyclic systems, placing a double bond at the bridgehead carbon induces physically impossible angle strain, forcing an unnatural planarity. Bredt's Rule explicitly forbids the formation of a double bond at a bridgehead in small rings, thus preventing the tautomerization.

💡 Solution & Explanation

Practice 22,000+ questions like this