Certain Aldehydes, ketone and certain alcohol undergo iodoform test. Certain Aldehydes ketones undergo aldol condensation. While certain aldehydes undergo Cannizzaro’s reaction. Aldehydes respond to Tollens’ reagent and Fehling’s reagent test.
Which amongst the following will respond to Tollen's reagent test.
A. C6H5CHO
B. HCHO
C. HCOOH
D. CH3COCH3
Choose the correct option
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, B and C only
Tollens’ reagent (ammoniacal silver nitrate) is a mild oxidising agent. Anything easily oxidised, like an aldehyde group, reduces it to metallic silver (silver mirror):
\( \displaystyle \ce{RCHO + 2[Ag(NH3)2]+ + 3OH- -> RCOO- + 2Ag v + 4NH3 + 2H2O} \)
A. \( \ce{C6H5CHO} \) — Responds. Aromatic aldehydes give the Tollens’ test (though not the Fehling’s test).
B. HCHO — Responds. An aldehyde.
C. HCOOH — Responds. Formic acid has an aldehydic H–C=O unit and is oxidised to \( \ce{CO2} \):
\( \displaystyle \ce{HCOOH + 2[Ag(NH3)2]+ + 2OH- -> CO2 + 2Ag v + 4NH3 + 2H2O} \)
D. \( \ce{CH3COCH3} \) — Does not respond. A ketone is not oxidised by mild reagents.
NCERT (2026-27 edition):
Tollens’ Test
