Grignard addition: phenylmagnesium bromide + benzaldehyde → diphenylmethanol
Reagent table at any scale. Enter how much benzaldehyde you have, or pick another reagent, and every mass, volume and amount follows.
Notes on the reagents
- Benzaldehyde
- Benzaldehyde — limiting reagent. Freshly distilled or wash with 5 % NaHCO3 then water to remove benzoic acid (white film on the bottle indicates oxidation). Anhydrous before use — Grignards quench instantly on water.
- Phenylmagnesium bromide
- Phenylmagnesium bromide — purchased as 1 M or 3 M solution in anhydrous Et2O or THF; never weighed as a solid. Slight excess (1.1 equiv) compensates for trace H2O in the substrate or solvent that consumes the Grignard.
- Diethyl ether
- Diethyl ether — anhydrous, sodium-dried. THF (CAS 109-99-9) is the modern alternative for less reactive Grignards but Et2O remains the textbook choice for PhMgBr addition to aromatic aldehydes.
- Diphenylmethanol
- Diphenylmethanol (benzhydrol) — white crystalline solid, mp 65–67 °C; recrystallises from hexane. Mild aromatic odour. Used as a starting material for benzhydrol-derived pharmaceuticals (diphenhydramine, etc.).
How the amounts are calculated
The amount you enter is converted to millimoles with the molar mass, or with density and molar mass for a volume. Dividing by its equivalents gives the millimoles per equivalent; every other reagent is that times its own equivalents. Masses use the molar mass of the structure. Volumes are given for compounds that are liquid at room temperature and have a density on file. A reagent sold as a solution, such as n-BuLi in hexanes, gets the volume of that solution; enter your bottle's titre and every volume follows.
The theoretical yield assumes full conversion of the limiting reagent: the reactant with the fewest millimoles per stoichiometric coefficient. Change an equivalent and the limiting reagent may change with it.
Solvent volume and concentration
The concentration refers to the substrate, the limiting reagent: solvent volume = millimoles of substrate ÷ concentration, since 1 M is 1 mmol/mL. Liquid reagents add to the final volume, so the real concentration ends up slightly lower. Leave the field empty to leave the solvent out.
What the table cannot know
Purity, water content and reagents sold as solutions. Grignard reagents and organolithiums are bought as solutions: take the millimoles from the table and divide by the molarity on the bottle to get the volume to syringe out.