Explain how does the presence or absence of hydrogen on nitrogen of amines affect the modes of their reactions with nitrous acid.

Explanation

To understand how the presence or absence of hydrogen on the nitrogen of amines affects their reactions with nitrous acid (HNO2), we can categorize amines into three types: primary, secondary, and tertiary amines. Each type reacts differently with nitrous acid due to the number of hydrogen atoms attached to the nitrogen atom.

### Step-by-Step Solution:

1. **Preparation of Nitrous Acid**:
- Nitrous acid is typically prepared in situ by mixing sodium nitrite (NaNO2) with concentrated hydrochloric acid (HCl). This reaction generates nitrous acid, which is used for further reactions with amines.

2. **Reaction of Primary Amines with Nitrous Acid**:
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