Purpose:
The purpose of this experiment is to be able to conduct an aldol condensation reaction using an unknown aldehyde and an unknown ketone. H NMR is used to identify the unknown aldehyde and ketone. Melting point is used to identify the aldol condensation reaction.
Theory:
Condensation reaction is also known as a dehydration reaction. In the mechanism of condensation reaction, a bond is formed between two molecules and creates water as a byproduct. Aldol condensation is a C-C bond forming reaction between the alpha carbon of the aldehyde or ketone and carbonyl carbon of another ketone or aldehyde. Aldol condensation is different from aldol condensation reaction. For aldol addition reaction, the alpha carbon of one aldehyde or ketone adds to the carbonyl group of the other ketone or aldehyde. This process creates a beta-hydroxy carbonyl, which is called aldol. For the aldol condensation reaction, the beta-hydroxy carbonyl that the alpha-hydrogen then goes on dehydration to form alpha-beta-unsaturated carbonyl compound.
Mechanism:
(Attached in Appendices)
Data:
Melting point of product: 204-206oC
Discussion:
For the H NMR, there are three distinct regions that can identify the product. The first peak is at 3.08 (singlet, 4H) represents four hydrogen atoms of the five membered ring. The second peak at 3.85 (singlet, 6H) represents the hydrogen atoms of the two methoxy groups. The last region is from 6.95 to 7.56 (multiplet, 10H) represents the hydrogen atoms of the benzene rings and the hydrogen atoms of vinyllic carbons. From the integration of H NMR spectra, the product is assumed to be 2,5-bis(4-methoxybenzylidene)cyclopentanone, which is a product of p-Anisaldehyde and cyclopentanone. The melting range was around 204-206oC. To consider the assumption above, the melting range of product using p-Anisaldehyde and cyclopentanone is around 212oC. The melting range of collected product was pretty close compare to the melting range of possible products using p-Anisaldehyde and cyclopentanone.
The Essay on The Aldol Condensation: Synthesis Of Dibenzalacetone
... rapid and reversible condensation reaction to occur. The product is a b-hydroxy aldehyde or ketone. This mechanism is known as an Aldol Condensation Reaction, a base ... then taken of both my crude product, as well as, my recrystallized product, resulting in identical melting points of 111-112oC, which indicate ...
Conclusion:
The product is 2,5-bis(4-methoxybenzylidene)cyclopentanone, which is a product of an aldol condensation using p-Anisaldehyde and cyclopentanone.
