Chemistry Aldehydes & Ketones SET 2019
PMDC Verified Question 55 of 94
Which one of the following reagents can be used to detect an aldehyde?
A
Tetraethyl lead
B
Alcoholic KOH
C
Acidified \( Cu_2Cl_2 \)
D
Tollen's reagent
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Propolis Cognitive Error Autopsy

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

Tollen's reagent is a classic, mild oxidizing agent specifically utilized to detect the presence of the easily oxidizable formyl group (\( -CHO \)).

Solution:

  • Tollen's reagent (ammoniacal silver nitrate) oxidizes aldehydes to carboxylate ions.


  • During the process, Silver(I) is reduced to elemental silver, forming a visible "silver mirror."


  • Ketones and most other functional groups do not react, making it highly specific for aldehydes.


Why other options are incorrect:

Tetraethyl lead was an anti-knock agent in gasoline. Alcoholic KOH is used for dehydrohalogenation (elimination reactions). Acidified copper chloride is not a standard aldehyde test.

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