If you have searched for dibenzylidene or the formula C17H14O, you were most likely looking for dibenzylideneacetone, usually abbreviated dba. It is a bright yellow solid best known for two things: a classic undergraduate experiment, and its role as a ligand in some of the most widely used palladium catalysts.
Key facts
| Name | Dibenzylideneacetone (1,5-diphenylpenta-1,4-dien-3-one) |
|---|---|
| Abbreviation | dba |
| Formula | C₁₇H₁₄O |
| Molar mass | 234.29 g/mol |
| CAS number | 538-58-9 (mixture of isomers is common; check the supplier) |
| Appearance | Yellow crystalline solid |
How dba is made
Dibenzylideneacetone is made by a Claisen–Schmidt condensation, a type of aldol reaction: two molecules of benzaldehyde react with one molecule of acetone in the presence of a base. Because the product precipitates as an attractive yellow solid, this is a favourite teaching experiment for introducing carbonyl chemistry, recrystallisation and melting point analysis.
Why chemists care: dba in palladium catalysis
dba’s biggest role today is as a weakly bound ligand on palladium(0). Two compounds are especially important:
- Tris(dibenzylideneacetone)dipalladium(0), Pd₂(dba)₃, often supplied as its chloroform adduct.
- Bis(dibenzylideneacetone)palladium(0), Pd(dba)₂.
Both are convenient, relatively air-stable sources of Pd(0). In use, the dba is displaced by phosphine or other ligands chosen for the reaction, generating the active catalyst for cross-coupling reactions such as Suzuki–Miyaura, Buchwald–Hartwig amination, Heck and Negishi couplings. These reactions underpin a large share of modern pharmaceutical and materials synthesis.
Tip: commercial Pd₂(dba)₃ varies in quality between batches and suppliers, and older material can contain palladium nanoparticles that change catalytic behaviour. Check the certificate of analysis, store under inert atmosphere in the fridge, and note the batch when reporting results.
Other uses
- Historically used as a UV-absorbing component in some sunscreen formulations.
- A common model compound in teaching labs for spectroscopy (UV-Vis, IR and NMR).
- A building block for further synthesis, including conjugate addition chemistry.
Buying and storing dba
- Order by CAS number, and check whether you need dba itself or a palladium complex; they have different CAS numbers and very different prices.
- Choose reagent grade for teaching; higher purity for catalyst preparation. See reagent grades.
- Store dba in a cool, dry place protected from light.
- Wear gloves and eye protection; avoid inhaling dust. Check the SDS for current hazard classification.
Frequently asked questions
What is C17H14O?
The molecular formula of dibenzylideneacetone (dba). Other compounds can share the formula, so confirm by name, structure or CAS number.
Why is Pd₂(dba)₃ purple while dba is yellow?
Binding to palladium changes how the molecule absorbs light, giving the complex its dark purple colour.
Is dba hazardous?
It is generally of low hazard compared with many lab chemicals, but you should still follow the supplier’s SDS and standard lab safety practice.
