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Grignard addition: phenylmagnesium bromide + benzaldehyde → diphenylmethanol

PhMgBr + Ph–CHO → [Ph2CH–OMgBr] →(H3O+) Ph2CH–OH

Textbook Grignard addition. Phenylmagnesium bromide (PhMgBr) attacks benzaldehyde's carbonyl carbon; aqueous acidic workup releases diphenylmethanol (benzhydrol). PhMgBr is bought as a 1 M or 3 M solution in anhydrous Et2O or THF — solid Grignards are not weighed. Reaction is run under N2 with rigorous water exclusion.

Conditions: Cool a flame-dried, N2-flushed flask to 0 °C. Charge anhydrous Et2O (~3 mL per mmol of benzaldehyde). Add benzaldehyde (1.0 equiv) by syringe; stir 5 min. Add PhMgBr (1.1 equiv, 1 M or 3 M solution in Et2O) dropwise over 10 min — exotherm; control addition rate to keep T < 5 °C. Warm to RT, stir 1–2 h. Workup — Quench cautiously with sat. NH4Cl (or 10 % HCl); extract with Et2O; wash organic with sat. NaHCO3 + brine; dry MgSO4. Concentrate. Recrystallise from hexane or hexane/EtOAc. White crystals; mp 65–67 °C.

Expected yield: 75–92 %
Expected duration: 1–2 h at RT after 0 °C addition

Mechanism reference ↗

Anchor reagent — fix this amount, scale everything else Substrate concentration · M

Amount r Unit

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Reactants

Reactants for Grignard addition: phenylmagnesium bromide + benzaldehyde → diphenylmethanol: stoichiometric quantities derived from the anchor amount.
Reagent	Equiv	Moles · mmol	Mass · g	Volume · mL
Phenylmagnesium Bromide 100-58-3 · C6H5BrMg density unavailable — volume not calculable.	1.1	11.00	1.995	—
Benzaldehyde 100-52-7 · C7H6O	1.0	10.00	1.061	1.01

Solvent

Solvent for Grignard addition: phenylmagnesium bromide + benzaldehyde → diphenylmethanol: stoichiometric quantities derived from the anchor amount.
Reagent	Equiv	Moles · mmol	Mass · g	Volume · mL
60-29-7 60-29-7 · C4H10O	—	609.58	45.182	63.64

Product

Product for Grignard addition: phenylmagnesium bromide + benzaldehyde → diphenylmethanol: stoichiometric quantities derived from the anchor amount.
Reagent	Equiv	Moles · mmol	Mass · g	Volume · mL
91-01-0 91-01-0 · C13H12O density unavailable — volume not calculable.	1.0	10.00	1.842	—

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: 91-01-0 91-01-0 · C13H12O
Theoretical max: 1.84 g (10.00 mmol)
Expected isolated · 75–92 % yield: 1.38 – 1.70 g

Stoichiometry: moles_X = (moles_anchor / equiv_anchor) × equiv_X. Mass = moles × MW; volume = mass / ρ. Solvent volume = total reactant moles ÷ substrate concentration.

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