Nitrogen is likely to be evolved when `NaNO_2` in dilute ` HCl` warmed with :

Options

A. ` CH_3NHCH_2CH_3`
B. `(C_(2)H_(5))_(3)N`
C. `C_6H_5NH_2`
D. `H_2NCH_2CH_2NH_2`

Explanation

To solve the question of when nitrogen is likely to be evolved when `NaNO_2` in dilute `HCl` is warmed with a specific type of amine, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Reaction Context**:
- The reaction involves sodium nitrite (NaNO2) and dilute hydrochloric acid (HCl). This combination is known to generate nitrous acid (HNO2), which can react with amines.

2. **Identify the Type of Amines**:
- Amines can be classified into primary, secondary, and tertiary amines.
- Primary amines (RNH2) are the only type that can produce nitrogen gas (N2) when reacted with NaNO2 and HCl.

3. **Reactions of Amines with NaNO2 and HCl**:
- When a primary amine reacts with NaNO2 and HCl, it forms a diazonium salt (RNH2 + NaNO2 + HCl → RN2+Cl−).
- This diazonium salt is unstable and can decompose upon heating to release nitrogen gas (N2).

4. **Evaluate Each Option**:
- **Option A**: Secondary amine - does not produce N2 as it forms a stable ammonium ion.
- **Option B**: Tertiary amine - does not react with NaNO2 and HCl, hence no N2 is produced.
- **Option C**: Aromatic amine - forms a stable diazonium salt (ArN2+), which does not release N2 under these conditions.
- **Option D**: Primary aliphatic amine - forms an unstable diazonium salt that decomposes to release nitrogen gas.

5. **Conclusion**:
- The correct answer is **Option D**, as it is the only option that involves a primary aliphatic amine, which will evolve nitrogen gas when warmed with NaNO2 in dilute HCl.