In order to get ethanethiol from bromoethane, the reagent used is :

Options

A. Sodium bisulphide
B. Sodium sulphide
C. Potassium thicyanate
D. Potassium sulphide

Explanation

To obtain ethanethiol (C2H5SH) from bromoethane (C2H5Br), we need to follow a series of steps to identify the appropriate reagent. Here is a step-by-step solution:

### Step 1: Identify the compounds involved
- **Bromoethane**: This is the starting compound, which has the formula C2H5Br. It consists of two carbon atoms (ethane) with a bromine atom attached.
- **Ethanethiol**: This is the desired product with the formula C2H5SH, which contains a thiol group (-SH) instead of the bromine atom.

### Step 2: Determine the reagent needed
To convert bromoethane to ethanethiol, we need a reagent that can replace the bromine atom with a thiol group. The reagent that provides the thiol group is **sodium bisulfide** (NaSH).

### Step 3: Write the reaction
The reaction can be represented as follows:
\[ \text{C2H5Br} + \text{NaSH} \rightarrow \text{C2H5SH} + \text{NaBr} \]
In this reaction, sodium bisulfide (NaSH) provides the -SH group that replaces the bromine atom in bromoethane.

### Step 4: Identify the type of reaction
This reaction is a nucleophilic substitution reaction (specifically an SN2 reaction) because:
- The nucleophile (SH-) attacks the electrophilic carbon atom bonded to bromine.
- Bromine acts as a leaving group, allowing the thiol group to take its place.

### Conclusion
The reagent used to obtain ethanethiol from bromoethane is **sodium bisulfide (NaSH)**.

### Final Answer
The correct answer is **option A: sodium bisulfide (NaSH)**.

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