Wittig olefination: methyltriphenylphosphonium bromide + benzaldehyde → styrene

Reagent table at any scale. Enter how much benzaldehyde you have, or pick another reagent, and every mass, volume and amount follows.

Conditions and workup
OBenzaldehydePh3PCH3Br (1.05 equiv)n-BuLi (1.05 equiv)THFStyrene70–88 %
OBenzaldehydePh3PCH3Br (1.05 equiv)n-BuLi (1.05 equiv)THFStyrene70–88 %

Reagent table

ReagentRoleEquivMW (g/mol)ρ (g/mL)nmV
Benzaldehyde100-52-7limitingyour amount reactant 106.12 1.050 94.2 mmol 10.0 g 9.52 mL
Methyltriphenylphosphonium bromide1779-49-3 reactant 357.23 — 98.9 mmol 35.3 g —
n-Butyllithium109-72-8 reagent 64.06 — 98.9 mmol 6.34 g 39.6 mL
Tetrahydrofuran109-99-9 solvent — 72.11 0.890 — — 188 mL
Styrene100-42-5 product — 104.15 0.910 94.2 mmol 9.81 g —
Theoretical yield9.81 g94.2 mmol of styrene
Expected at 70–88 %6.87 g – 8.64 gtypical isolated yield
Solvent188 mLTetrahydrofuran, 0.5 M
Limiting reagentBenzaldehyde
Notes on the reagents
Benzaldehyde
Benzaldehyde — the substrate aldehyde; freshly distilled to remove benzoic acid (white film on bottle indicates oxidation).
Methyltriphenylphosphonium bromide
Methyltriphenylphosphonium bromide — ylide precursor; slight excess so the aldehyde is the limiting reagent.
Tetrahydrofuran
Tetrahydrofuran — anhydrous; degas with N2 sparge before use. DMSO is a common alternative when NaH is the base instead of n-BuLi.
Styrene
Styrene — colourless liquid, bp 145 °C; polymerises on standing (stabilise with 4-tert-butylcatechol if storing). Pungent sweet odour.
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.

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