Which of the following compounds will reacts with ethanolic KCN ?

Options

A. Ethyl chloride
B. Acetyl chloride
C. Chlorobenzene
D. Benzaldehyde

Explanation

To determine which compounds will react with ethanolic KCN, we need to analyze the reactivity of each compound towards nucleophilic substitution reactions. Here’s a step-by-step breakdown:

### Step 1: Understand the Reactivity of KCN
Ethanolic KCN (potassium cyanide in ethanol) provides cyanide ions (CN⁻), which act as nucleophiles. Nucleophiles can attack electrophilic centers in molecules, leading to substitution reactions.

**Hint:** Remember that nucleophiles are attracted to electrophilic centers, which are typically carbon atoms bonded to electronegative atoms.

### Step 2: Analyze Each Compound
1. **Ethyl Chloride (C2H5Cl)**:
- Ethyl chloride has a carbon atom bonded to a chlorine atom (C-Cl bond).
- The carbon is electrophilic, and the cyanide ion can attack it, leading to the substitution of the chlorine atom.
- **Reaction:** C2H5Cl + KCN → C2H5CN + KCl (Nucleophilic substitution occurs).

2. **Acetyl Chloride (CH3C(=O)Cl)**:
- Acetyl chloride has a carbonyl group (C=O) which makes the carbon atom bonded to chlorine highly electrophilic.
- The cyanide ion can attack this carbon, resulting in the substitution of chlorine.
- **Reaction:** CH3C(=O)Cl + KCN → CH3C(=O)CN + KCl (Nucleophilic substitution occurs).

3. **Chlorobenzene (C6H5Cl)**:
- Chlorobenzene has a chlorine atom bonded to a benzene ring.
- The carbon in chlorobenzene is less electrophilic due to the resonance stabilization of the benzene ring.
- The nucleophilic attack by cyanide is not favorable, and thus no reaction occurs.
- **Conclusion:** Chlorobenzene does not react with ethanolic KCN.

4. **Benzaldehyde (C6H5CHO)**:
- Benzaldehyde has a carbonyl group (C=O) attached to a benzene ring.
- The carbonyl carbon is electrophilic and can be attacked by the cyanide ion.
- **Reaction:** C6H5CHO + KCN → C6H5C(OH)(CN) (Nucleophilic addition occurs).

### Step 3: Summarize the Results
- **Compounds that react with ethanolic KCN:**
- Ethyl Chloride (C2H5Cl)
- Acetyl Chloride (CH3C(=O)Cl)
- Benzaldehyde (C6H5CHO)

- **Compound that does not react:**
- Chlorobenzene (C6H5Cl)

### Final Answer
The compounds that will react with ethanolic KCN are Ethyl Chloride, Acetyl Chloride, and Benzaldehyde.

---