Claisen-Schmidt aldol: benzaldehyde + acetone → benzalacetone
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 indicates oxidation).
- Acetone
- Acetone — large excess (5 equiv) to suppress double-condensation to dibenzylideneacetone (DBA). Also serves as a co-solvent.
- Sodium hydroxide
- Sodium hydroxide — catalytic base; deprotonates acetone's α-carbon. Aqueous, dissolved into the EtOH/H2O reaction medium.
- Ethanol
- Ethanol (95 % aqueous) — primary reaction medium. The 5 % water is part of the kinetic control: anhydrous EtOH overpowers the elimination step.
- 4-Phenyl-3-buten-2-one
- Benzalacetone (4-phenyl-3-buten-2-one, E-isomer) — pale-yellow needles; mp 41–42 °C; recrystallises from EtOH; mild floral odour. Skin sensitiser — gloves.
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.