I. INTRODUCTION

The aldol condensation relies on the reactivity of a carbonyl group that can build a new carbon-carbon bond. This reaction is considered as one of the most proficient method that is used to form a carbon-carbon bond. There are many types of aldol condensation, and for this experiment the cross aldol condensation was employed. This reaction is between aldehydes and ketone that produces a mixed condensation products. In this reaction, the enolate ion of one compound undergoes nucleophilic addition to the carbonyl carbon of a different compound. Its products are usually detrimental since there is atendency of reduced yielded product due to the mixture of products. Below is the figure of the crossed aldol condensation main reaction of this experiment. This experiment condensation produces an -unsaturated ketone dibenzaldehyde.

The purpose of this experiment was to synthesize dibenzaldehyde via aldol condensation reaction between acetone and benzaldehyde. This is by mixing the two reactants with NaOH and ethanol and swirled occasionally for 15 minutes to allow reaction. The crystal s were then collected by vacuum filtration while washing it with water and chilled ethanol to encourage recrystalization.

II. METHODOLOGY

A. MATERIALS/ CHEMICALS/ APPARATUS

50-mL Erlenmeyer flask0.4 g NaOH (in 2-mL water)

Beaker0.3-mL acetone

Aspirator0.8-mL benzaldehyde

PipetEthyl acetate

Buchner funnel95% ethanol

Filter paper

Wash bottle

B. PROCEDURE

A solution of 0.4 g NaOH in 2-mL H2O + 2-mL 95% ethanol was prepared in an erlenmeyer flask. The solution was then cooled. Into the solution, a 0.3 mL acetone and a 0.8 mL benzaldehyde was added. The flask was then swirled from time to time for 15 minutes to allow reaction. The product was then filtered using a Buchner funnel via vacuum filtration. The crystals were then washed with H2O and then with chilled 95% ethanol. The crystals were then weighted and the percentage yield was calculated.

III. DATA/ RESULTS/ CALCULATIONS

Table 1. Reagents and propertiesSubstanceFormula, g/molAmount usedMole ratioDensity, g/mL

Aetone58.080.3-mL1:10.731

Benzaldehyde106.120.8-mL2:11.044

NaOH400.4N/AN/A

Dibenzalacetone224productN/AN/A

Solving for theoretical yield.Conversion: mL of A grams of A moles of A moles of D grams of DNote: A-acetone; D- dibenzaldehydeAcetone:

Conversion: mL of B grams of B moles of B moles of D grams of DNote: B-benzaldehyde; D- dibenzaldehydeBenzaldehyde:

Since Acetone was the limiting reagent thus will be the theoretical value as well.

Table 2. Weight of NaOHWeight of watchglass + NaOH (g)32. 07

Weight of watchglass (g)31.67

Weight of NaOH (g)0.400

Table 3. Weight of crystals/productWeight of filter paper + crystals (g)0.9463

Weight of filter paper (g)0.3500

Weightof crystals (g)0.5963

Calculation of percentage yield

= 70. 48%

IV. DISSCUSSION/ INTERPRETATION OF RESULTS

Aldol condensation reactions represent an important class of reaction for forming carbon-carbon bonds. In this experiment the cross aldol condensation was performed. The synthesis began with a strong base, NaOH, to generate the acetone enolate ion. Water then forms as a byproduct of the reaction. This reaction strongly favors the starting acetone and based in the shown calculation acetone here was the limiting reagent and thus produces only on small quantity but because the enolate is nucleophilic, it attacks the carbonyl of the benzaldehyde and formed a -carbonyl alkoxide ion. This alkoxide ion attacks the protons from the water molecule and formed a - hydroxyl ketone. On the other hand, NaOH attracks another acidic -hydrogen and stabilizes the carbocation and formed an -unsaturated ketone. The ketone undergone the same enolate condensation reaction with the second mole of benzaldehyde since this ketone still have the -hydrogen, which is acidic, and produced the dibenzalacetone.The aldol condensation reaction between acetone and benzaldehyde yielded dibenzalacetone crystals. The percentage yield for the reaction was 70.48%. The low percentage yield was due to the fact that many crystals were lost during the removal of the solvent from the reaction mixture during the comdensation of acetone with benzaldehyde. Some crystals were also lost during the washing of crystals with water. Also, not all of the crystals remained in the filter paper. Some was filterd right through the paper with the solvent and ended up in the bottom of the flask. These personal error contributed to the low percentage yield obtained. On loophole, in theory, was that the reaction is a mixture of product thus it was expected to produce a lower yield and therefore contributed to the low percentage yield.

V. CONCLUSION AND RECCOMENDATION

The purpose of this experiment was to synthesize dibenzalacetone through aldol condensation of acetone and benzaldehyde. The experiment yielded the crystals which was an indication of a successful experiment. Though there were errors that resulted to low percentage yield it can be avoided by considering the lapses mentioned earlier. One thing to avoid such errors is by carefully selecting the starting materials where only one reactant has an enolized -hydrogen and can minimize the formation of mistures. The other one is the SOP of most recommendations handling and performing the experiments more vigilantly.