Urotropine is obtained when

Options

A. urea reacts with formalin
B. urea reacts with ammonia
C. formaldehyde reacts with ammonia
D. acetone reacts with ammonia

Answer

To determine how urotropine is obtained, we need to analyze the given options and the chemical reactions involved. Urotropine, also known as hexamine or methenamine, is formed through a specific reaction.

### Step-by-Step Solution:

1. **Identify the Reactants**: The question presents four options regarding the formation of urotropine. The relevant reactants are urea, formaldehyde, ammonia, and acetone.

2. **Understanding Urotropine**: Urotropine is a compound with the formula \( \text{C}_6\text{H}_{12}\text{N}_4 \). It is known for its use as an antiseptic in urinary tract infections and has applications in various industries.

3. **Analyzing the Chemical Reaction**: The correct reaction for the formation of urotropine involves formaldehyde and ammonia. The balanced chemical equation for this reaction is:
\[ 6 \text{HCHO} + 4 \text{NH}_3 \rightarrow \text{C}_6\text{H}_{12}\text{N}_4 + 4 \text{H}_2\text{O} \]
Here, formaldehyde (HCHO) reacts with ammonia (NH₃) to produce urotropine and water.

4. **Selecting the Correct Option**: Based on the analysis of the reaction, the correct option is that urotropine is obtained when formaldehyde reacts with ammonia.

### Final Answer:
Urotropine is obtained when formaldehyde reacts with ammonia (Option 3).

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