Question

(i) Explain Aldol condensation with example.
(ii) How are the following conversions achieved: 
(a) Benzene  Benzaldehyde, (b) Ethanoic acid  ethanol.

• A.
• B.
• C.
• D.

Hint:

For the cumene process, remember that acetone is a valuable by-product, making this the most economical industrial route to phenol.

Answer 1

The Correct Option is A

Step 1: Aldol Condensation.
Aldehydes or ketones containing at least one alpha-hydrogen undergo a reaction in the presence of dilute alkali to form beta-hydroxy aldehydes (aldols).
Example:
2 CH3CHO → CH3CH(OH)CH2CHO (in presence of dilute NaOH)

Step 2: Specific Conversions.

(a) Benzene to Benzaldehyde: Gatterman-Koch Reaction.
Benzene is treated with CO and HCl in the presence of anhydrous AlCl3.
C6H6 + CO + HCl → C6H5CHO (in presence of anhydrous AlCl3)

(b) Ethanoic Acid to Ethanol:
Reduction using a strong reducing agent like Lithium Aluminium Hydride.
CH3COOH → CH3CH2OH (i) LiAlH4/ether, (ii) H3O+