Which is NOT a reason why enamines are good nucleophiles.

• A. Nitrogen is less electronegative than oxygen.
• B. The second-best resonance contributor shows an anion on the α-carbon.
• C. Nitrogen is a base.
• D. Nitrogen is a good electron-donating group.

Answer: (C)

Verified step by step guidance

1. Understand the structure of enamines: Enamines are compounds containing a nitrogen atom bonded to a carbon-carbon double bond. This structure allows for resonance, which is key to their nucleophilic behavior.
2. Consider the electronegativity of nitrogen: Nitrogen is less electronegative than oxygen, which means it holds onto its electrons less tightly, making it more willing to donate electrons and act as a nucleophile.
3. Analyze resonance contributors: The second-best resonance structure of an enamine places a negative charge on the α-carbon, enhancing its nucleophilicity by stabilizing the negative charge through resonance.
4. Evaluate the role of nitrogen as a base: While nitrogen can act as a base, this property does not directly contribute to the nucleophilicity of enamines. Instead, it is the electron-donating ability of nitrogen that enhances nucleophilicity.
5. Assess the electron-donating ability of nitrogen: Nitrogen's ability to donate electrons makes enamines good nucleophiles, as it increases the electron density on the carbon-carbon double bond, facilitating nucleophilic attack.