Dibenzylacetone

Synthesis of Dibenzylacetone

Background

The aldol condenstation in this experiment is the acid or base catalyzed self-condensation of an aldehyde to give an β-hydrixyaldehyde. Also, in this reaction, a carbon-carbon bond is formed between the α-carbon of one molecule and the carbonyl carbon of the other. Dehydration of the aldol products to give α, β-unsaturated carbonyl compounds can be accomplished by simply heating the products. Heating the products gives the desired products.

The first step in the mechanism is the deprotonation of an a-hydrogen by a strong base to form a resonance-stablized enolate ion. Although is only partially converted to an enolate ion, the enolate is very reactive and will add to the carbonyl of an aldehyde. A b-hydroxyaldehyde, which can undergo base-catalyzed elimination upon heating to yield an α,β- unsaturated aldehyde, is the initial product of the aldol condensation. Dehydration will occure readily if the new double bond is conjugated with an aromatic ring. A mixed aldol condenstation is a reaction that occurs between two different kinds of aldehydes or ketones. For it to work, at least one of the compounds has to be an aldehyde. This condensation is generally practical only if one of the components being used has no acidic α-hydrogens. If it has them, then up to four products can be formed, lowering yields of product wanted. Dibenzylacetone was formed via a mixed aldol condensation between two equivalents of benzaldehyde and acetone.

Experimental Procedure

1) Directions for the experiment were followed according to page 408-409 of the book

Results

Acetone Added (Limiting Reagent) | Theoretical Yield | Actual Yield | Percent Yield | Known MP | Observed MP |

.073 mL | .000996 moles.233 g | .000804 moles.188 g | 80.6% | 110-111 C | 109-111 C |

Discussion

The aldol condensation in this experiment is base catalyzed, which is why NaOH was added to the reaction mixture. The melting point...