The Aldol Condensation: Synthesis of Dibenzalacetone
Objective:
The benefit of this lab was to acquaint oneself with the fundamentals of the Aldol Condensation reaction by demonstrating the synthesis of dibenzalacetone (trans, trans-1,5-Diphenyl-1,4-pentadien-3-one) through the aldol condensation of acetone with benzaldehyde. The synthesis began by using a strong base to generate the acetone enolate ion. The ketone/enol tautomerization is an equilibrium process that produces little of the enol (ppm or less). However, any enol that formed quickly reacted with the strong base to form the enolate ion. Therefore, the generation of the enolate drove this reaction to completion (Le Chatelier's principle). Being a very strong nucleophile, this enolate attacked the carbonyl of benzaldehyde and formed an alkoxide ion. This alkoxide ion abstracted a proton from water to form a beta keto alcohol which then tautermerizes to an enol. This enol reacted with base to form yet another enolate. Finally, the enolate lost a hydroxide ion to form an alpha, beta unsaturated ketone. Since the newly formed ketone still possessed alpha hydrogens, it too underwent the same enolate condensation reaction with a second mole of benzaldehyde to form the final product, dibenzalacetone.
Background information was obtained on all aspects of this mechanism, fiddling with such concepts as equilibrium shifting, possible limitations, and symmetrical versus mixed aldols. The final product, dibenzalacetone, was weighed in order to calculate the percent yield. A melting point was then taken to properly characterize the final product.
Abstract:
The experimental procedure followed the format referenced in the lab manual Chemical Education Resources: Chem 236, Synt 720. The only experiment performed with the assistance of this lab manual was on page 101-103, Semi-Microscale Aldol Condensation.
Discussion:
A majority of biomolecules, such as, carbohydrates, lipids, proteins, nucleic acids, and numerous others, are biosynthesized through pathways that
The benefit of this lab was to acquaint oneself with the fundamentals of the Aldol Condensation reaction by demonstrating the synthesis of dibenzalacetone (trans, trans-1,5-Diphenyl-1,4-pentadien-3-one) through the aldol condensation of acetone with benzaldehyde. The synthesis began by using a strong base to generate the acetone enolate ion. The ketone/enol tautomerization is an equilibrium process that produces little of the enol (ppm or less). However, any enol that formed quickly reacted with the strong base to form the enolate ion. Therefore, the generation of the enolate drove this reaction to completion (Le Chatelier's principle). Being a very strong nucleophile, this enolate attacked the carbonyl of benzaldehyde and formed an alkoxide ion. This alkoxide ion abstracted a proton from water to form a beta keto alcohol which then tautermerizes to an enol. This enol reacted with base to form yet another enolate. Finally, the enolate lost a hydroxide ion to form an alpha, beta unsaturated ketone. Since the newly formed ketone still possessed alpha hydrogens, it too underwent the same enolate condensation reaction with a second mole of benzaldehyde to form the final product, dibenzalacetone.
Background information was obtained on all aspects of this mechanism, fiddling with such concepts as equilibrium shifting, possible limitations, and symmetrical versus mixed aldols. The final product, dibenzalacetone, was weighed in order to calculate the percent yield. A melting point was then taken to properly characterize the final product.
Abstract:
The experimental procedure followed the format referenced in the lab manual Chemical Education Resources: Chem 236, Synt 720. The only experiment performed with the assistance of this lab manual was on page 101-103, Semi-Microscale Aldol Condensation.
Discussion:
A majority of biomolecules, such as, carbohydrates, lipids, proteins, nucleic acids, and numerous others, are biosynthesized through pathways that