Tools · Synthesis
Reaction Scale Calculator
Pick a stored reaction, fix one reagent's amount, get every other reagent's quantity by stoichiometric equivalents. Solvent volume derived from your substrate concentration. Densities + molar masses come from our molecule database.
Switch reaction
Press / to jump here from anywhere. Type to search all 3374 reactions.
Cannizzaro disproportionation: 2 benzaldehyde → benzyl alcohol + sodium benzoate
2 Ph–CHO + NaOH → Ph–CH2–OH + Ph–COO⁻ Na⁺
Textbook redox disproportionation of an α-H-free aldehyde. Concentrated NaOH drives hydride transfer between two benzaldehyde molecules: one is reduced to benzyl alcohol, the other oxidised to sodium benzoate. Mechanism goes through a tetrahedral hydride-donor intermediate; chemists isolate the products by acidifying the aqueous phase to precipitate benzoic acid and ether-extracting the alcohol.
Conditions: Dissolve NaOH (1.1 equiv per pair of aldehyde, ~50 wt% aq.) in water. Add benzaldehyde (2.0 equiv) — exotherm; cool with an ice bath to keep T < 30 °C during addition. Stir vigorously (the system rapidly thickens to a paste as the disproportionation advances). Continue stirring 4–24 h at RT until a single phase forms. Workup — Dilute with cold water; extract benzyl alcohol into Et2O (3×). Acidify the aqueous phase with conc. HCl to pH < 2 — benzoic acid precipitates as white needles. Filter, wash with cold water, dry. Recrystallise from hot water. α-H-free aldehydes are the substrate scope (benzaldehyde, furfural, formaldehyde): if the aldehyde has α-H, aldol condensation outcompetes Cannizzaro at the same conditions.
- Expected yield
- 70–88 %
- Expected duration
- 4–24 h at RT after 0–30 °C base addition
Computed quantities
Reactants
| Reagent | Equiv | Moles · mmol | Mass · g | Volume · mL |
|---|---|---|---|---|
|
Benzaldehyde
100-52-7 · C7H6O
|
2.0 | 20.00 | 2.122 | 2.02 |
Catalyst
| Reagent | Equiv | Moles · mmol | Mass · g | Volume · mL |
|---|---|---|---|---|
|
Sodium Hydroxide
1310-73-2 · HNaO
|
1.1 | 11.00 | 0.440 | 0.21 |
Solvent
| Reagent | Equiv | Moles · mmol | Mass · g | Volume · mL |
|---|---|---|---|---|
|
Water
7732-18-5 · H2O
|
— | 1720.31 | 31.000 | 31.00 |
Product
| Reagent | Equiv | Moles · mmol | Mass · g | Volume · mL |
|---|---|---|---|---|
|
Benzyl Alcohol
100-51-6 · C7H8O
|
1.0 | 10.00 | 1.081 | 1.04 |
|
65-85-0
65-85-0 · C7H6O2
|
1.0 | 10.00 | 1.221 | 0.96 |
Expected isolated yield
What you should actually weigh out of the recrystallisation flask, scaled from the limiting reactant via the canonical-procedure yield window.
- Product
- Benzyl Alcohol 100-51-6 · C7H8O
- Theoretical max
- 1.08 g (10.00 mmol)
- Expected isolated · 70–88 % yield
- 0.76 – 0.95 g
Stoichiometry: moles_X = (moles_anchor / equiv_anchor) × equiv_X.
Mass = moles × MW; volume = mass / ρ. Solvent volume = total reactant moles ÷ substrate concentration.