Sciencemadness Discussion Board

Dibenzalacetone - Organic Synthesis writeup

vibbzlab - 26-4-2020 at 09:37

Dibenzalacetone is a pale yellow organic compound which was earlier used in sunscreen because it has the ability to absorb UV light

link to preparation demonstration

Dibenzalacetone an organic compound formed through the famous aldol reaction called Claisen-Schmidt condensation reaction

Materials required
Sodium hydroxide 3.15g
Benzaldehyde - 3.2ml
Acetone - 2.3ml
Ethyl alcohol - 25ml
Distilled water - 30ml
Ice water bath

Step 1 is to make a solution of sodium hydroxide
Take 3.15g Sodium hydroxide keep it in a 100ml beaker kept in icebath and add 25ml ethyl alcohol and 30ml distilled water to make a solution of it. Allow it to cool in ice bath.

Step 2
In a seperate 50ml beaker mix together 3.2ml benzaldehyde and 2.3ml acetone.
After a thorough mixing we pipette out half of the mixture

Step 3
Transfer the pipetted mixture into the Cooled Sodium hydroxide solution slowly with constant stirring.
by about 1minute a white fluffy precipitate is formed.
continue stirring for another 15minutes

Whats happening here is 2molecules of Benzaldehyde reacts with 1 molecule of acetone on both its alpha carbons
Let us continue.

After 15 minutes add the rest of the mixture of benzaldehyde and acetone and continue stirring gently for 30minutes.
Slowly a pale yellow precipitate forms.
After 30minutes stop stirring and filter the solution to collect the precipitate.
Ice cold water can be used to purify the product.(DBA is insoluble in water)
Further purification can be done by recrystallising usinge ethyl alcohol (DBA is soluble in ethanol)

IMG_20200422_054107.jpg - 1.4MBIMG_20200420_121924.jpg - 2.1MB

Boffis - 26-4-2020 at 23:14

Intersting synthesis. Have you tried this with other aromatic aldehydes?

I tried this with cinnamaldehyde, salicylaldehyde, anisaldehyde and vanillin both as disubstituted and mono substituted derivatives and I am still trying to sort out what was produced. Anisaldehyde reacted as expected, so did cinnamaldehyde but the products are hard to purify, with vanillin I struggled to identify/purify the product and with salicyladehyde I got two products but with unexpected properties.

vibbzlab - 28-4-2020 at 07:38

i dont have the other aromatic aldehydes. I would definetly love to do the synthesis if i can get my hands on those chemicals

njl - 28-4-2020 at 08:52

@vibbzlab I have a bit of piperonal with your name on it if you'd like. Might be useful for opening up some positions to substitution?

vibbzlab - 2-5-2020 at 20:03

didnt quite get you xD.

G-Coupled - 3-5-2020 at 11:39

Quote: Originally posted by vibbzlab  
didnt quite get you xD.

They appear to be kindly offering to send you some Piperonal to do with as you will.

That's nice. :cool: