What are the products of the following reactions? Explain briefly and solve it correctly
1) cyclopentanone + cyclohexylamine.
2) 3-pentanone + butylamine.
3) 3-pentanone + cyclohexylamine.
The Correct Answer and Explanation is :
Reactions and Their Products
These reactions involve ketones and amines, leading to the formation of imines (Schiff bases) through a condensation reaction. The general mechanism follows these steps:
- Nucleophilic Attack: The amine attacks the carbonyl carbon of the ketone.
- Formation of Carbinolamine: A tetrahedral intermediate is formed.
- Dehydration: Loss of water results in the formation of an imine (Schiff base).
Let’s analyze each reaction:
1) Cyclopentanone + Cyclohexylamine
Reaction:
Cyclopentanone (a five-membered cyclic ketone) reacts with cyclohexylamine (a six-membered cyclic primary amine). The nucleophilic nitrogen of cyclohexylamine attacks the carbonyl carbon, followed by dehydration, forming N-cyclohexylcyclopentylideneimine.
Product:
N-Cyclohexylcyclopentylideneimine (Cyclopentanone imine derivative)
2) 3-Pentanone + Butylamine
Reaction:
3-Pentanone is a symmetrical ketone. Butylamine (a primary amine) attacks the carbonyl carbon of 3-pentanone, leading to imine formation.
Product:
N-Butylpentan-3-imine (3-Pentanone imine derivative)
3) 3-Pentanone + Cyclohexylamine
Reaction:
Similar to reaction 2, but using cyclohexylamine instead of butylamine. The reaction leads to imine formation.
Product:
N-Cyclohexylpentan-3-imine (3-Pentanone imine derivative)
Explanation (300 Words)
The reactions between ketones and primary amines form imines (Schiff bases). These reactions are acid-catalyzed and involve nucleophilic addition followed by water elimination.
- Mechanism:
- The lone pair of electrons on the nitrogen attacks the partially positive carbonyl carbon.
- This forms a tetrahedral intermediate known as carbinolamine.
- The carbinolamine loses water to form a C=N imine bond.
- Why Only Primary Amines Work:
- Primary amines (R-NH₂) readily form imines because they have an extra hydrogen to eliminate as water.
- Secondary amines (R₂-NH) lead to enamines instead of imines.
- Reactivity and Stability:
- The reaction favors imine formation under mild acidic conditions (pH 4–5).
- Aromatic amines react slower due to resonance stabilization.
- Applications:
- Imines are intermediates in organic synthesis.
- Used in biochemistry (Schiff base formation in enzymes).
Thus, these reactions efficiently convert ketones into Schiff bases, which are important for further synthetic transformations.
Now, I’ll generate an image of the reaction products.
Here is the reaction scheme showing the imine (Schiff base) formation for the given reactions. Let me know if you need any modifications or further explanations!