ChemistryAldehydes, ketones and carboxylic acidsClass 12

Carbonyl, Aldol & Cannizzaro reactions: interactive simulation

The carbon-oxygen double bond in aldehydes and ketones is strongly polarized (C^δ+ = O^δ-), making the carbonyl carbon an electrophilic hotspot. The presence or absence of an α-hydrogen dictates whether a compound undergoes Aldol condensation or Cannizzaro disproportionation.

Useful for: JEE Main, JEE Advanced, NEET, CBSE Boards · 4 modes in one lab

What you can explore

  1. 1

    Nucleophilic Carbonyl Addition

    Grignard and HCN attacks yielding 1°, 2°, 3° alcohols and cyanohydrins.
  2. 2

    Aldol Condensation

    Enolate formation, aldol intermediate and conjugated crotonaldehyde dehydration.
  3. 3

    Cannizzaro Redox Disproportionation

    Hydride transfer disproportionation of aldehydes lacking α-hydrogens.
  4. 4

    Fischer Esterification

    Acid-catalysed condensation of carboxylic acid and alcohol yielding fragrant esters.

Try this

Explore Grignard addition to synthesize 1°, 2° and 3° alcohols, follow enolate ion formation in Aldol condensation leading to conjugated α,β-unsaturated aldehydes, and witness hydride transfer in the Cannizzaro reaction.

  1. 1

    In Nucleophilic Addition, switch substrate from Formaldehyde to Aldehyde to Ketone with Grignard reagent.

    What you should see

    Formaldehyde produces 1° alcohol, other aldehydes yield 2° alcohol, and ketones yield 3° alcohol!

  2. 2

    In Aldol Condensation, step from Aldol intermediate to Dehydration.

    What you should see

    Heating eliminates water to form But-2-enal (Crotonaldehyde), which is stabilized by conjugation between C=C and C=O.

  3. 3

    In Cannizzaro sim, observe products of Benzaldehyde.

    What you should see

    One molecule is reduced to Benzyl alcohol (C₆H₅CH₂OH) while the other is oxidized to Potassium benzoate (C₆H₅COOK).

Formulas behind it

Aldol Condensation reaction

2CH3CHO→dil. NaOHCH3CH(OH)CH2CHO→ΔCH3CH=CH-CHO+H2O2 \text{CH}_3\text{CHO} \xrightarrow{\text{dil. NaOH}} \text{CH}_3\text{CH(OH)CH}_2\text{CHO} \xrightarrow{\Delta} \text{CH}_3\text{CH=CH-CHO} + \text{H}_2\text{O}

Cannizzaro Disproportionation

2C6H5CHO+conc. KOH→ΔC6H5CH2OH+C6H5COOK2 \text{C}_6\text{H}_5\text{CHO} + \text{conc. KOH} \xrightarrow{\Delta} \text{C}_6\text{H}_5\text{CH}_2\text{OH} + \text{C}_6\text{H}_5\text{COOK}

Grignard Reaction (Formaldehyde → 1° Alcohol)

HCHO+RMgX→etherRCH2OMgX→H3O+RCH2OH\text{HCHO} + R\text{Mg}X \xrightarrow{\text{ether}} R\text{CH}_2\text{OMg}X \xrightarrow{\text{H}_3\text{O}^+} R\text{CH}_2\text{OH}

Common mistakes

  • Attempting Cannizzaro reaction with an aldehyde having an α-hydrogen (like acetaldehyde) — it undergoes rapid Aldol condensation instead.
  • Thinking ketones cannot undergo Aldol reaction. Ketones do undergo aldol (ketol) reactions, but equilibrium lies mostly towards reactants due to steric hindrance.
  • Believing oxygen in ester comes from the carboxylic acid — isotopic ¹⁸O labeling proves the ester oxygen comes from the alcohol.
Stuck on a carbonyl, aldol & cannizzaro reactions question?Snap it and get a whiteboard video solution.

FAQ

Why is the α-hydrogen of an aldehyde acidic?

Because the enolate conjugate base formed upon deprotonation is resonance-stabilized by delocalizing negative charge onto the electronegative oxygen atom.

What is a Cross-Aldol condensation?

An aldol reaction between two different aldehydes or ketones, yielding up to four products unless one partner lacks α-hydrogens.

What is the rate-determining step in Cannizzaro reaction?

The intermolecular transfer of hydride ion (H⁻) from the tetrahedral intermediate to the second aldehyde molecule.

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