Tollen's reagent oxidise aldehydes in a medium(A) to the corresponding compound(B).
(A) and (B) respectively are:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → alkaline ; carboxylate anion
Tollens’ reagent, \( \ce{[Ag(NH3)2]^{+}} \), works in an alkaline medium, so the acid formed is neutralised at once and stays as the carboxylate anion:
\( \displaystyle \ce{RCHO + 2[Ag(NH3)2]^+ + 3OH^- -> RCOO^- + 2Ag + 2H2O + 4NH3} \)
Why the other options are incorrect
Option (1) acidic ; carboxylic acid — Incorrect. The reagent is not acidic; acid would destroy the silver–ammonia complex.
Option (2) alkaline ; carboxylic acid — Incorrect. The medium is right, but a free carboxylic acid cannot remain in a basic solution; it is present as \( \ce{RCOO^{-}} \) until the solution is acidified.
Option (3) acidic ; carboxylate anion — Incorrect. The carboxylate anion is right, but the medium is alkaline.
NCERT (2026-27 edition):
Tollens’ Test
