Aldehydes and Ketones — Preparation

• Preparing aldehydes and ketones via oxidation of alcohols with specific reagents.
• Ozonolysis of alkenes to give aldehydes/ketones.
• Rosenmund reduction for converting acid chlorides to aldehydes.
• Etard reaction and Grignard reagent approach to carbonyl compounds.

Level 1 — Oxidation of alcohols

Primary alcohol → Aldehyde: Use PCC (pyridinium chlorochromate, mild) or Cu at 300°C. R−CH₂OH → R−CHO (stop at aldehyde). Strong oxidant (KMnO₄/H⁺) gives carboxylic acid directly.

Secondary alcohol → Ketone: Use K₂Cr₂O₇/H₂SO₄ or KMnO₄/H⁺. R−CH(OH)−R' → R−CO−R' (ketone, cannot oxidise further under mild conditions).

Tertiary alcohol: Cannot be oxidised to aldehyde or ketone (no H on C−OH).

Example: Propan-2-ol → propan-2-one (acetone) with K₂Cr₂O₇/H₂SO₄.

Level 2 — Ozonolysis, Rosenmund, Etard, Grignard

Ozonolysis: Alkene + O₃ → ozonide → (Zn/H₂O) → aldehydes and/or ketones. Terminal alkene → one aldehyde + one product (HCHO from terminal =CH₂). Internal symmetrical alkene → two identical aldehydes/ketones.

Rosenmund reduction: Acid chloride (RCOCl) + H₂ / Pd-BaSO₄ (catalyst poisoned) → aldehyde RCHO. Pd-BaSO₄ is poisoned to prevent further reduction to alcohol. This is the key synthesis of aldehydes from acid chlorides.

Etard reaction: Toluene (C₆H₅CH₃) + CrO₂Cl₂ (chromyl chloride) → benzaldehyde (C₆H₅CHO). Chromyl chloride oxidises −CH₃ directly on ring to −CHO.

From Grignard reagent:

• RMgX + HCOOEt (ethyl formate) → after hydrolysis → primary alcohol (two R groups? wait: RMgX + HCHO → 1° alcohol; RMgX + RCHO → 2° alcohol; RMgX + ketone → 3° alcohol.
• More relevant for preparation: CO₂ + RMgX → RCOOH (not carbonyl, but same Grignard logic).
• Ethyl orthoformate or DMF + RMgX → aldehyde after hydrolysis (standard synthesis).

JEE tip: Rosenmund → aldehyde (not alcohol — catalyst is poisoned). Clemmensen/Wolff-Kishner reduce C=O; Rosenmund gives aldehyde FROM acid chloride.

NCERT spotlight — Stephen reduction

Nitrile (RCN) + SnCl₂/HCl → imine salt → (H₃O⁺) → aldehyde RCHO (Stephen's reduction). Useful for one-carbon homologation of aldehyde synthesis. Contrast with LiAlH₄ reduction of nitrile → amine.

Gattermann-Koch synthesis: Benzene + CO + HCl (AlCl₃/CuCl, pressure) → benzaldehyde. Industrial synthesis of aromatic aldehydes.

Using Rosenmund reduction, show the synthesis of propanal from propanoic acid.

Step 1 — Convert propanoic acid to propanoyl chloride:
  CH₃CH₂COOH + SOCl₂ → CH₃CH₂COCl + SO₂ + HCl.
Step 2 — Rosenmund reduction:
  CH₃CH₂COCl + H₂ → (Pd/BaSO₄, quinoline catalyst poison) → CH₃CH₂CHO + HCl.
Step 3 — Product: propanal (propionaldehyde) ✓.
Step 4 — Why Pd/BaSO₄? Prevents over-reduction to propan-1-ol.
  Without poisoning: CH₃CH₂COCl + 2H₂ → CH₃CH₂CH₂OH (unwanted).

Applications — fragrances and flavours

Benzaldehyde (from Etard or Gattermann-Koch): almond flavour, perfumery. Acetaldehyde: industrial precursor to acetic acid, ethyl acetate. Acetone: common solvent in nail polish remover, industrial cleaning. Aldehydes and ketones are crucial synthetic intermediates in pharmaceutical industry.

• How would you convert cyclohexanol to cyclohexanone? Give reagent.
• Write the product of ozonolysis of CH₃CH=CHCH₃ followed by Zn/H₂O.
• What is the purpose of BaSO₄ in Rosenmund reduction?

Open the Practice tab for graded questions on Preparation of Aldehydes/Ketones.

• Use the platform-native live simulation or PhET-style tool for this topic (number line, Venn, physics playground, molecule builder, sensor dashboard, etc.).
• Mirror / body / home activity: physically do the concept (count objects, measure, role-play) and photograph or describe for portfolio.
• Voice or text reflection with AI Mentor: explain the concept to a younger student or family member.

• "Explain this concept to a Class 6 student using one real example from an Indian home, school, market, or festival."
• "What is one common mistake students make here, and how would you catch yourself making it?"
• Stretch: "How does this connect to coding, robotics, money, health, environment, or a future career?"

• Complete the core practice + one extension activity (photo, table, short reflection, or mini-project) for base XP + topic badge.
• 5-7 day streak or family discussion note = multiplier + visible artifact in parent/principal dashboard.
• Best real-world application stories (anonymised) featured on class or national leaderboard.

• One hands-on project or measurement using the Drishti kit or household items that makes the concept physical.
• Direct link to at least one Future Skill track (Money Management, Green Tech, Cyber Defenders, Micro-Entrepreneurship, AI Mastery, Sustainable Living, Personality Development).
• Coding extension where relevant (simple script, simulation, or data logging).

This material emphasises experiential "learning by doing", competency (apply/create/analyse), vocational exposure, critical thinking, and multidisciplinary connections. Designed to feed live worlds, AI Mentor (with memory), gamification, robotics, parent analytics, and future skills — not just exam prep.

Portfolio Evidence Idea: Your photo/table/reflection/project + one sentence on "How this helps me in real life or a possible future path."

Open the Practice tab for aligned questions (easy/medium/hard + case-based) with full AI scaffolding.

See curriculum for cross-links and the full future-skills/robotics chapters.