Condensation of Pentane-2,4-dione with excess of Ammonia

Introduction:
When a carbonyl compound such as Pentane-2,4-dione condenses with excess ammonia, it forms a class of compounds known as diimines. Diimines are organic compounds that contain two nitrogen atoms connected by a double bond.

Explanation:
To determine the number of different diimines that would be obtained on the condensation of Pentane-2,4-dione with excess ammonia, we need to consider the various possible combinations of the carbonyl compound and ammonia.

Step 1: Formation of imine
The first step in the condensation reaction is the formation of an imine. In this step, a nitrogen atom from ammonia replaces the oxygen atom in the carbonyl group of Pentane-2,4-dione. This results in the formation of an imine, which contains a carbon-nitrogen double bond.

Step 2: Formation of diimine
In the presence of excess ammonia, the imine can undergo further condensation reactions. The second nitrogen atom from ammonia can replace the oxygen atom in another molecule of Pentane-2,4-dione, resulting in the formation of a diimine.

Types of diimines:
There are two possible types of diimines that can be obtained from the condensation of Pentane-2,4-dione with excess ammonia:

1. Symmetrical diimine: In this type of diimine, both nitrogen atoms are connected to the same carbon atom in the molecule. The resulting diimine is symmetrical in nature.

2. Unsymmetrical diimine: In this type of diimine, the two nitrogen atoms are connected to different carbon atoms in the molecule. The resulting diimine is unsymmetrical in nature.

Number of different diimines:
The number of different diimines that can be obtained depends on the number of possible combinations of the carbonyl compound and ammonia. In the case of Pentane-2,4-dione, there are two carbon atoms that can be involved in the condensation reaction. Therefore, there are two possible combinations:

1. Condensation of the carbonyl group with the carbon atom adjacent to it.
2. Condensation of the carbonyl group with the carbon atom two positions away.

Conclusion:
In conclusion, when Pentane-2,4-dione condenses with excess ammonia, two different diimines can be obtained: one symmetrical diimine and one unsymmetrical diimine. The number of different diimines is determined by the number of possible combinations of the carbonyl compound and ammonia.