The alkyl halide `C_4 H_9 Br `(A) reacts with alcoholic KOH and gives an alkene (B) which reacts with bromine to give a dibromide (C). (C) is transformed with sodamide into a gas (D) which forms a precipitate when passed through ammoniacal silver nitrate solution. Give the structural formulae of the compounds (A), (B), (C) and (D) and explain the reactions involved.

Explanation

To solve the problem step by step, we will identify the compounds A, B, C, and D based on the given reactions and their structural formulas.

### Step 1: Identify Compound A
The alkyl halide is given as `C4H9Br`. The only possible structure that fits this formula is **1-bromobutane**.

**Structure of A:**
\[ \text{A: } \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Br} \]

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