An organic compound A contains 69.77% C, 11.63% H and the rest oxygen; its molecular mass is 86. It does not reduce Tollens' reagent but forms an addition product with sodium hydrogen sulphite and gives a positive iodoform test. On vigorous oxidation it gives ethanoic and propanoic acids. Write the possible structure of compound A.
Answer: A = pentan-2-one, CH₃COCH₂CH₂CH₃.
Solution
Empirical analysis: C 69.77/12 = 5.81, H 11.63/1 = 11.63, O 18.6/16 = 1.16 → ratio 5:10:1 → CHO (mass 86 ✓).
No Tollens' ⇒ a ketone; bisulphite adduct ⇒ methyl ketone/unhindered carbonyl; iodoform positive ⇒ CHCO– present.
Vigorous oxidation → CHCOOH + CHCHCOOH ⇒ cleavage of CHCO–CHCH.
No Tollens' ⇒ a ketone; bisulphite adduct ⇒ methyl ketone/unhindered carbonyl; iodoform positive ⇒ CHCO– present.
Vigorous oxidation → CHCOOH + CHCHCOOH ⇒ cleavage of CHCO–CHCH.
CBSE Class 12 Board · 2008 · All India; also Foreign · Subjective