Ethylamine `underset ( Hg Cl _2 ) overset ( CS _2 ) to A overset( HOH ) to B [B ] ` is :

Options

A. Ethyl isothiocyanate
B. Ethyl isocyanide
C. Ethyl alcohol
D. Ethyl amine

Answer

To solve the problem, we will follow the steps of the reactions involving ethylamine, CS2, and water (HOH).

### Step-by-Step Solution:

1. **Identify the Reactants:**
- The starting compound is ethylamine (C2H5NH2).

2. **Reaction with CS2:**
- Ethylamine reacts with carbon disulfide (CS2) in the presence of mercuric chloride (HgCl2). This reaction is known as the Hofmann mustard oil reaction.
- The product formed from this reaction is an isothiocyanate. The general reaction can be represented as:
\[ \text{C2H5NH2} + \text{CS2} \xrightarrow{\text{HgCl2}} \text{C2H5NCS} \]
- Here, C2H5NCS is ethyl isothiocyanate.

3. **Hydrolysis of Isothiocyanate:**
- The next step involves the hydrolysis of ethyl isothiocyanate (C2H5NCS) in the presence of water (HOH).
- During hydrolysis, the isothiocyanate reacts with water to form a thiocarbamic acid:
\[ \text{C2H5NCS} + \text{H2O} \rightarrow \text{C2H5NHSO} + \text{HCl} \]
- The product formed is N-ethyl thiocarbamic acid (C2H5NHSO).

4. **Final Product:**
- The thiocarbamic acid is unstable and can further decompose to yield ethylamine (C2H5NH2) again:
\[ \text{C2H5NHSO} \rightarrow \text{C2H5NH2} \]
- Thus, the final product B is ethylamine.

### Conclusion:
The final product B is ethylamine (C2H5NH2).