The compounds CH3CH2CHO and CH3COCH3 can be distinguished from each other using

Analysis

The question asks us to distinguish between two organic compounds: CH₃CH₂CHO (propanal) and CH₃COCH₃ (propanone).

• CH₃CH₂CHO is an aldehyde.
• CH₃COCH₃ is a ketone.

To distinguish between them, we need a chemical test that reacts with aldehydes but does not react with ketones.

Concept: Oxidation of Carbonyl Compounds

• Aldehydes are easily oxidized to carboxylic acids because they possess a hydrogen atom attached to the carbonyl carbon.
• Ketones are resistant to mild oxidation because they lack that hydrogen atom.

Common laboratory reagents used to distinguish aldehydes from ketones include Tollen's reagent and Fehling's solution/Benedict's solution.

Step-by-Step Solution

1. Analyze the Reagents: • Tollen's reagent (Ammoniacal silver nitrate): When heated with an aldehyde, it is reduced to metallic silver, forming a "silver mirror" on the walls of the test tube. Ketones do not react with Tollen's reagent. • Benedict's solution: When heated with an aliphatic aldehyde, it produces a reddish-brown precipitate of copper(I) oxide. Ketones do not react with Benedict's solution.

2. Evaluate the Options: • A (Dilute ammonia): Does not react with either to give a distinct visual difference. • B (Benedict's solution): While this can distinguish them, Tollen's reagent is the classic, most definitive textbook reagent for this specific distinction in JAMB chemistry. • C (Tollen's reagent): This is the standard reagent used to identify aldehydes. The formation of a silver mirror confirms the presence of the aldehyde (propanal), while the ketone (propanone) remains unchanged. • D (Sodium hydroxide): Used in condensation reactions, but not as a primary diagnostic test to distinguish these two.

3. Conclusion: Both B and C are chemically capable of distinguishing them; however, in the context of JAMB and standard chemistry examinations, Tollen's reagent is the primary and most widely cited answer for distinguishing aldehydes from ketones.

Tip for your Exam

Remember the mnemonic "Aldehydes are Silver-tongued": Aldehydes react with Tollen's reagent to form a silver mirror. Ketones are "stubborn" and do not react with mild oxidizing agents like Tollen's or Benedict's.