If 1,3–dibromopropane reacts with zinc dust, the product obtained is:

Options

A. Propene
B. Propane
C. Cyclopropane
D. Hexane

Answer

To determine the product obtained when 1,3-dibromopropane reacts with zinc dust, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**:
The reactant is 1,3-dibromopropane, which has the structure:
\[ \text{Br-CH}_2\text{-CH}_2\text{-CH}_2\text{-Br} \]
This compound has bromine atoms attached to the first and third carbon atoms of a three-carbon chain.

2. **Understand the Reaction with Zinc Dust**:
Zinc dust is a reducing agent. In this reaction, zinc will donate electrons to the carbon atoms that are bonded to bromine (Br). The electronegativity of bromine means that it pulls electron density away from the carbon, making the carbon electron-deficient.

3. **Formation of Carbanions**:
When zinc donates electrons to the carbon atoms, it can lead to the formation of carbanions. The bromine atoms will leave as bromide ions (Br⁻), and the carbon atoms will gain a negative charge:
\[ \text{Br-CH}_2\text{-CH}_2\text{-CH}_2\text{-Br} + \text{Zn} \rightarrow \text{CH}_2\text{-CH}_2\text{-CH}_2\text{-ZnBr} \]

4. **Elimination Reaction**:
The carbanions formed can undergo an elimination reaction. The negatively charged carbon can attack the bromine on the adjacent carbon, leading to the release of bromide ions and the formation of a double bond:
\[ \text{CH}_2\text{-CH}_2\text{-CH}_2\text{-ZnBr} \rightarrow \text{Cyclopropane} + \text{ZnBr}_2 \]

5. **Final Product**:
The final product of this reaction is cyclopropane, and zinc bromide (ZnBr₂) is released as a byproduct.

### Conclusion:
The product obtained when 1,3-dibromopropane reacts with zinc dust is **cyclopropane**.