Question

How will you convert the following:
(i) Toluene to benzoic acid.
(ii) Ethanol to propan-2-ol.
(iii) Propanal to 2-hydroxy propanoic acid.

Hint:

The oxidation of toluene with potassium permanganate is a strong method to obtain benzoic acid. Hydration of propene and reduction of aldehydes are common transformations in organic synthesis.

Answer 1

1. Toluene to benzoic acid: Toluene can be oxidized to benzoic acid by treating it with potassium permanganate (KMnO\(_4\)). \[ C_6H_5CH_3 + KMnO_4 \to C_6H_5COOH \] This is a typical oxidation reaction where the methyl group (-CH\(_3\)) is oxidized to a carboxyl group (-COOH).

2. Ethanol to propan-2-ol: Ethanol can be converted to propan-2-ol by using a suitable catalyst for a reduction reaction. For example, it can be oxidized to acetaldehyde (CH\(_3\)CHO), which is then reduced to propan-2-ol using a reducing agent like lithium aluminum hydride (LiAlH\(_4\)). \[ C_2H_5OH \xrightarrow{[O]} C_2H_4O \xrightarrow{LiAlH_4} C_3H_7OH \] Alternatively, it can be directly hydrated from propene.

3. Propanal to 2-hydroxy propanoic acid: Propanal can be converted to 2-hydroxy propanoic acid by the hydroxylation reaction, specifically by adding a hydroxyl group to the alpha-carbon of the aldehyde. A suitable reagent for this transformation is hydroxylamine or a mild oxidizing agent. \[ C_3H_7CHO + OH^- \to C_3H_6(OH)COOH \]