Which of the following can NOT be formed through the stork enamine reaction with 2-butanone? 

• A. 3-pentanone
• B. 3-methyl-2-butanone
• C. 2-octanone
• D. 3-octanone

Answer: (C)

Verified step by step guidance

1. Understand the Stork enamine reaction: It involves the formation of an enamine from a ketone and a secondary amine, followed by an alkylation or acylation step.
2. Identify the starting material: In this case, the ketone is 2-butanone, which will form an enamine with a secondary amine.
3. Consider the possible alkylation or acylation reactions: The enamine can react with an alkyl halide or an acyl chloride to form a new carbon-carbon bond.
4. Analyze the products: 3-pentanone and 3-methyl-2-butanone can be formed by alkylation of the enamine with appropriate alkyl halides. However, forming 2-octanone would require a different starting ketone or a more complex reaction pathway.
5. Conclude which product cannot be formed: Since 2-octanone cannot be formed directly from 2-butanone through a simple Stork enamine reaction, it is the correct answer.