An unsaturated hydrocarbon X on ozonolysis gives A. Compound A when warmed with ammonical silver nitrate forms a bright silver mirror along the sides of the test tube. The unsaturated hydrocarbon X is:
(A)(see structure)
(B)(see structure)✓ Correct
(C)(see structure)
(D)(see structure)
Answer: (B)
Solution
The silver mirror with ammoniacal silver nitrate shows that the ozonolysis product reduces Tollens' reagent, so it must carry an aldehydic hydrogen. Oxidative cleavage of a carbon-carbon triple bond gives carboxylic acids, and a terminal alkyne HC≡C−R gives methanoic acid together with RCOOH; methanoic acid still holds a −CHO unit and so deposits the mirror. The tetrasubstituted alkene and the alkene carrying a cyclopropane ring cleave to ketones alone, and the internal alkyne gives only ethanoic acid, so none of those responds. The hydrocarbon is but-1-yne, HC≡C−CH2−CH3.
JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Single correct option
