CBSE 2025, Set 2

Question

Give a simple chemical test to distinguish between butan-1-ol and butan-2-ol.

Edvaya · Accepted Answer

The correct answer is Subjective. **Test: Iodoform test (NaOH + I₂)** **Butan-2-ol** (secondary alcohol, CH₃CH(OH)CH₂CH₃) gives a **positive iodoform test** — it contains the CH₃–CHOH– group, which is oxidised to CH₃CO– (methyl ketone intermediate) and then triiodomethane (CHI₃) is formed as a **yellow precipitate**. **Butan-1-ol** (primary alcohol, CH₃CH₂CH₂CH₂OH) does **not** give iodoform test — it lacks the CH₃–CHOH– structural unit. $$	ext{CH}_3	ext{CH(OH)CH}_2	ext{CH}_3 \xrightarrow{	ext{NaOH}+	ext{I}_2} 	ext{CHI}_3 \downarrow (	ext{yellow}) \quad 	ext{(butan-2-ol)}$$ $$	ext{CH}_3	ext{CH}_2	ext{CH}_2	ext{CH}_2	ext{OH} \xrightarrow{	ext{NaOH}+	ext{I}_2} 	ext{No yellow precipitate} \quad 	ext{(butan-1-ol)}$$

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Chemistry > Organic Chemistry > Alcohols Phenols And Ethers

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