Which will react with ethanotic KCN?

Options

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

Answer

To determine which compounds will react with ethanolic KCN, we need to analyze the reactivity of each compound based on the presence of a suitable leaving group and the nature of the carbon atom to which the leaving group is attached.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to consider:
- Ethyl chloride (C2H5Cl)
- Acetyl chloride (CH3COCl)
- Chlorobenzene (C6H5Cl)
- Benzaldehyde (C6H5CHO)

2. **Understand the Role of KCN**: KCN (potassium cyanide) acts as a nucleophile. Nucleophiles are species that can donate an electron pair to form a chemical bond. In this case, the cyanide ion (CN⁻) will attack electrophilic carbon atoms.

3. **Analyze Ethyl Chloride (C2H5Cl)**:
- Ethyl chloride has a chlorine atom attached to a primary carbon.
- The chlorine atom is a good leaving group, and the carbon is electrophilic due to the electronegativity of chlorine.
- **Reaction**: CN⁻ will attack the carbon, displacing Cl⁻.
- **Conclusion**: Ethyl chloride will react with ethanolic KCN.

4. **Analyze Acetyl Chloride (CH3COCl)**:
- Acetyl chloride has a chlorine atom attached to a carbonyl carbon (C=O).
- The carbonyl carbon is electrophilic because of the partial positive charge due to the electronegative oxygen.
- **Reaction**: CN⁻ will attack the carbonyl carbon, displacing Cl⁻.
- **Conclusion**: Acetyl chloride will react with ethanolic KCN.

5. **Analyze Chlorobenzene (C6H5Cl)**:
- Chlorobenzene has a chlorine atom attached to a benzene ring.
- The carbon attached to chlorine is part of a stable aromatic system, and the lone pairs of chlorine are in conjugation with the benzene ring, making it less reactive.
- **Conclusion**: Chlorobenzene will NOT react with ethanolic KCN.

6. **Analyze Benzaldehyde (C6H5CHO)**:
- Benzaldehyde has a carbonyl group (C=O) attached to a benzene ring.
- The carbonyl carbon is electrophilic due to the electronegative oxygen.
- **Reaction**: CN⁻ will attack the carbonyl carbon, leading to the formation of a cyanohydrin.
- **Conclusion**: Benzaldehyde will react with ethanolic KCN.

### Final Conclusion:
The compounds that will react with ethanolic KCN are:
- Ethyl chloride (C2H5Cl)
- Acetyl chloride (CH3COCl)
- Benzaldehyde (C6H5CHO)

Chlorobenzene (C6H5Cl) will NOT react.