CBSE Class 12 · 2011 · Delhi · Alcohols Phenols and EthersShort Answer

How would you obtain:
i) picric acid (2,4,6-trinitrophenol) from phenol
ii) 2-methylpropene from 2-methylpropanol

Solution

(i) Treat phenol first with concentrated H

_{2}

_{4}

(→ phenol-2,4-disulphonic acid), then with concentrated HNO

_{3}

C_{6} H_{5} OH conc. H_{2} S O_{4} conc. HN O_{3} 2, 4, 6 - (N O_{2})_{3} C_{6} H_{2} OH (picric acid)

(direct nitration would oxidise the ring).
(ii) Acid dehydration — the 1° cation rearranges (hydride shift) to the 3° cation, which loses a β-H:

(C H_{3})_{2} CHC H_{2} OH conc. H_{2} S O_{4} Δ (C H_{3})_{2} C = C H_{2} + H_{2} O

CBSE Class 12 Board · 2011 · Delhi · Subjective