The end product of the reaction,
Ethyl amine `overset(HNO_(2))rarr(A)overset(PCl_(5))rarr(B)overset(KCN)rarr(C )` `(C)` is,

Options

A. Propanenitrile
B. Trethylamine
C. diethylamine
D. propylamine

Answer

To determine the end product (C) of the given reaction sequence involving ethyl amine, we will break down each step of the reaction as follows:

### Step 1: Reaction of Ethyl Amine with HNO2
- **Reaction**: Ethyl amine (C2H5NH2) reacts with nitrous acid (HNO2).
- **Product (A)**: This reaction forms an unstable diazonium salt. The diazonium salt formed is C2H5N2^+ (ethyl diazonium ion), which can be represented as C2H5-N≡N^+.
- **Mechanism**: The nitrogen in HNO2 reacts with the ethyl amine to form the diazonium salt. The reaction can be summarized as:
\[ C2H5NH2 + HNO2 \rightarrow C2H5N2^+ + H2O \]

### Step 2: Reaction of Diazonium Salt with PCl5
- **Reaction**: The diazonium salt (A) reacts with phosphorus pentachloride (PCl5).
- **Product (B)**: The diazonium ion undergoes a substitution reaction to form ethyl chloride (C2H5Cl).
- **Mechanism**: The diazonium salt loses nitrogen gas (N2) and forms a carbocation, which then reacts with Cl^- from PCl5:
\[ C2H5N2^+ + PCl5 \rightarrow C2H5Cl + N2 + POCl3 \]

### Step 3: Reaction of Ethyl Chloride with KCN
- **Reaction**: Ethyl chloride (B) reacts with potassium cyanide (KCN).
- **Product (C)**: This reaction leads to the formation of propionitrile (C2H5C≡N), which is also known as ethyl cyanide.
- **Mechanism**: The reaction proceeds via an SN2 mechanism, where the cyanide ion (CN^-) attacks the electrophilic carbon in ethyl chloride:
\[ C2H5Cl + KCN \rightarrow C2H5C≡N + KCl \]

### Final Product
Thus, the final product (C) of the entire reaction sequence is **propionitrile (C2H5C≡N)**.

### Summary of Products
- A: Ethyl diazonium ion (C2H5N2^+)
- B: Ethyl chloride (C2H5Cl)
- C: Propionitrile (C2H5C≡N)