E-Aldol-Condensation

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Data Sheet – Experiment 19
Aldol Condensation
Name: _____________________________ / Locker: _______
Synthesis of Dibenzalacetone
O
O
H
excess
H3C
O
CH3
NaOH(aq) / EtOH
Benzaldehyde: (MW = 106.12 g/mol)) (d= 1.0415 g/ml) (Bp. 178.1˚C)
Acetone: (MW = 58.08 g/mol) (d = 0.79 g/ml) (Bp. 56.53˚C)
Dibenzalacetone: (MW = 234.29)
The reaction that you will be performing in lab is an example of a mixed aldol
condensation. You will be combining an ethanolic sodium hydroxide solution containing an
enolizable ketone (acetone) with the non-enolizable benzaldehyde.
Mechanism:
Procedure:
In a 100 ml Erlenmeyer flask prepare a solution of 1.2g of sodium hydroxide in 6ml of water and
6 ml of 95% ethanol. After the solution has cooled, add 1ml acetone and then 2.5 ml of
benzaldehyde. A yellow turbidity will appear almost immediately, which will turn into a
flocculent precipitate. Swirl the flask from time to time over a 15 minute period. Collect the
mushy reaction product on a Büchner funnel and wash it first with water and then a little (5ml)
chilled 95% ethanol. Recrystallize your product from ethyl acetate. Isolate your product by
vacuum filtration with a Buchner funnel. Dry your product and obtain a melting point.
Note: 1. Use no more than 5ml for recrystallization
2. m.p. of dibenzalacetone (110-111ºC)
1
Data Sheet – Experiment 6
Aldol Condensation
Melting point of your dibenzalacetone: _________________ºC
Actual yield: ___________ grams
Theoretical yield calculation:
Theoretical yield: __________ grams
Percent yield calculation:
Percent yield: __________ %
Discussion:
2
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