The correct order of boiling points of the following isomeric amines is `C_4H_9NH_2,(C_2H_5)_2NH,C_2H_5N(CH_3)_2`

Options

A. `C_2H_5N(CH_3)_2 gt (C_2H_5)NH gt C_4H_9NH_2`
B. `(C_2H_5)_2NH gt C_2H_5N(CH_3)_2 gt C_4H_9NH_2`
C. `(C_4H_9)NH_2 gt (C_2H_5)_2NH gt C_2H_5N(CH_3)_2`
D. `(C_2H_5)_2NH gt C_4H_9NH_2 gt C_2 H_5 (CH_3)_2`

Answer

To determine the correct order of boiling points for the isomeric amines \(C_4H_9NH_2\), \((C_2H_5)_2NH\), and \(C_2H_5N(CH_3)_2\), we need to analyze the structures and the type of amines involved.

### Step 1: Identify the Structures of the Amines
1. **\(C_4H_9NH_2\)**: This is a primary amine. The nitrogen is attached to one carbon chain and has two hydrogen atoms.
2. **\((C_2H_5)_2NH\)**: This is a secondary amine. The nitrogen is attached to two ethyl groups and has one hydrogen atom.
3. **\(C_2H_5N(CH_3)_2\)**: This is a tertiary amine. The nitrogen is attached to one ethyl group and two methyl groups, with no hydrogen atoms attached to nitrogen.

### Step 2: Determine the Type of Hydrogen Bonding
- **Primary Amines**: Can form strong hydrogen bonds due to the presence of two hydrogen atoms attached to nitrogen. This leads to higher boiling points.
- **Secondary Amines**: Can form hydrogen bonds but are less effective than primary amines since they have only one hydrogen atom available for bonding.
- **Tertiary Amines**: Cannot form hydrogen bonds because there are no hydrogen atoms attached to the nitrogen.

### Step 3: Compare the Boiling Points
- **Primary Amine \(C_4H_9NH_2\)**: Highest boiling point due to strong hydrogen bonding.
- **Secondary Amine \((C_2H_5)_2NH\)**: Lower boiling point than the primary amine due to weaker hydrogen bonding.
- **Tertiary Amine \(C_2H_5N(CH_3)_2\)**: Lowest boiling point as it cannot form hydrogen bonds.

### Conclusion: Order of Boiling Points
Based on the analysis:
- Highest boiling point: \(C_4H_9NH_2\) (Primary Amine)
- Middle boiling point: \((C_2H_5)_2NH\) (Secondary Amine)
- Lowest boiling point: \(C_2H_5N(CH_3)_2\) (Tertiary Amine)

Thus, the correct order of boiling points is:
\[ C_4H_9NH_2 > (C_2H_5)_2NH > C_2H_5N(CH_3)_2 \]