Oxygen-Containing Organic Compounds — A/L Chemistry

What must I remember about Oxygen-Containing Organic Compounds?

• Alcohols undergo oxidation: 1° alcohols oxidize to aldehydes then carboxylic acids; 2° oxidize to ketones; 3° resist oxidation under normal conditions.
• Phenols are significantly more acidic than alcohols due to resonance stabilization of the negative charge on the phenoxide ion over the aromatic benzene ring.
• Aldehydes and ketones undergo nucleophilic addition at the carbonyl carbon and react with 2,4-dinitrophenylhydrazine (2,4-DNP) to form orange/yellow precipitates.
• Carboxylic acids react with carbonates to liberate CO₂ gas and undergo esterification with alcohols in the presence of concentrated H₂SO₄.
• Relative acidity hierarchy: Carboxylic acids > Phenols > Water > Alcohols > Alkynes.

Test yourself (1 minute)

1. Lucas test distinguishes alcohols

   3° gives immediate turbidity, 2° gives turbidity within 5 minutes, 1° remains clear at room temperature.

2. Which two reagents tell an aldehyde from a ketone, and what does each show?

   Tollens' reagent (ammoniacal silver nitrate) and Fehling's solution are reduced by aldehydes (silver mirror and red Cu₂O precipitate) but not ketones.

3. What does the iodoform test detect, and what does a positive result look like?

   Iodoform test (I₂/NaOH) yields a pale yellow CHI₃ precipitate with compounds containing CH₃-CH(OH)- or CH₃-C=O groups.

Practise Oxygen-Containing Organic Compounds questions today

Source: NIE G.C.E. (A/L) Chemistry Syllabus (Unit 9)

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Grade 12 · Term 3