Chemistry Aldehydes & Ketones MDCAT 2011
PMDC Verified Question 93 of 94
Consider the following reaction:

$$ R-CHO + 2[Ag(NH_3)_2]OH \longrightarrow RCOONH_4 + 2Ag \downarrow + 2NH_3 + H_2O $$

This reaction represents which of the following tests?
A
Fehling test
B
Benedict test
C
Ninhydrin test
D
Tollen's test
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Tollen's test
Concept:

Tollens' reagent is an ammoniacal solution of silver nitrate, containing the diamminesilver(I) complex ion, \( [Ag(NH_3)_2]^+ \).

Solution:

  • Aldehydes readily reduce the \( Ag^+ \) ions in Tollens' reagent to elemental silver (\( Ag \)).


  • The elemental silver deposits on the inner walls of the test tube, creating a characteristic "silver mirror."


  • The aldehyde itself is oxidized to a carboxylate salt.


Why other options are incorrect:

Fehling's and Benedict's tests utilize Copper(II) complexes and produce a brick-red precipitate of Copper(I) oxide. Ninhydrin test is used for detecting amino acids, not aldehydes.

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