वह यौगिक जो नीचे दिखाई गई aldol संगनन अभिक्रिया से प्राप्त नहीं किया जा सकता है, वह है

Aldol condensation between 3,3-dimethylcyclopentanone and benzaldehyde requires alpha-hydrogens from the ketone. Since 3,3-dimethylcyclopentanone has only one methyl-adjacent alpha-carbon with alpha-hydrogens, specific crossed aldol products are formed, ruling out certain structures.