Shake occasionally for 30 minutes. Take a TLC at the end of the period. Add 2 mL of H2O into the tube to wash the crystals and remove using a pipette.
Repeat 3 times. Run an IR to determine the quality of the product. This could be an indication of low product quality and the presence of impurities in the crystals of the product. Taking Rf values during the performance of the experiment helps track the progress of the reaction and determine the ending point of reaction.
Clamp the flask to prevent it from tipping. Collect the solid using vacuum filtration. Note: Be sure to record the mass of the filter paper before placing it in the vacuum funnel.
Prepare to wash and dry the solid. Wash with cold distilled water. Rinse the solid with 5—8 drops of ethanol. Keep the vacuum filtration on for an additional 10 minutes to help air dry the solid.
Weigh the dried solid on the filter paper and record the mass to 0. Part II Recrystallization Monitor the temperature with a Wide-Range Temperature Probe or thermometer. Transfer your crude product to a test tube and add about 5 mL of ethanol. Use the minimum amount of solvent needed to dissolve your solid.
Crystals will not form if too much ethanol is used. Stir the solution with the glass stirring rod for 5 minutes. If the solid does not dissolve, add 0. After no more liquid is coming through the filter paper, disconnect the filter flask from the vacuum line, wash the solid with 10 mL water and, after about one minute, reconnect to the vacuum. Allow air to be sucked around the crystals for about 2 minutes.
Recrystallize your product from ethyl acetate using a water bath and hot plate to heat the solvent. You can use a medium test tube or a small Erlenmeyer flask. Be careful. Weigh your product and determine percent yield. What reactant is your percent yield based on? Determine the melting point and compare to the literature value.
Table 1 and 2 Table 1. If contacted, remove with plenty of water. In a medium size tube, mix 2mL of benzaldehyde with 15 drops of acetone, and leave it at room temperature for 5 minutes.
Then, add the mixture to the ethanol-NaOH solution in small portions and stir with magnetic stirrer if available for 30 minutes. Chill the solution in an ice-water bath. Collect the yellow crystals by suction filtration and hand-dry them by pressing them between dry paper towels. Determine the weight of the dibenzalacetone product, its melting point, and the percent yield. Return the product to your instructor.
NOTE- The amounts of the reagents used in this reaction are very important to ensure the correct product forms. In a given example a student added twice as much acetone as the procedure called for.
Since there would be such an excess of acetone the benzaldehyde would only see acetone and would not end up adding twice to any acetone molecules.Rinse the solid with 5—8 drops of ethanol. Return the product to your instructor. This conjugated enone synthesis is catalyzed by both acids and bases. NOTE- The amounts of the reagents used in this reaction are very important to ensure the correct product forms.
Prepare to wash and dry the solid. In this experiment, you will run an aldol condensation between an aldehyde and a ketone and then the product of the reaction precipitates out of solution and can be collected by filtration. If contacted, remove with plenty of water. Thus at higher temperature in base the aldol reaction will go directly to the conjugated enone without any isolation of the aldol intermediate. This would give an end product of benzalacetone instead of dibenzalacetone.
Compound Mol. Clamp the round bottom flask to a ring stand and lower the flask onto the stir plate. Since there would be such an excess of acetone the benzaldehyde would only see acetone and would not end up adding twice to any acetone molecules. You can use a medium test tube or a small Erlenmeyer flask.
Synthesis of Dibenzalacetone by Aldol Condensation advertisement Experiment Synthesis of Dibenzalacetone by Aldol Condensation 19 py The aldol condensation is a reaction between two aldehydes or ketones, catalyzed by a base or acid, generating a molecule having both alcohol and aldehyde functional groups. This is of course quite different than the chemistry of normal alcohols.
If student added two fold of acetone the acetone will react with itself and the product would be isolated as diacetone alcohol or mesityl oxide. Since there would be such an excess of acetone the benzaldehyde would only see acetone and would not end up adding twice to any acetone molecules. References: Mahrwald, R. What product would you expect to obtain from aldol cyclization of hexanedioal in basic solution. Draw the mechanism for the formation of the product.
In a medium size tube, mix 2mL of benzaldehyde with 15 drops of acetone, and leave it at room temperature for 5 minutes.
It is extremely important that one of the carbonyl groups has an acidic alpha hydrogen one adjacent to a carbonyl group so that the enolate ion can be formed. The fact that the Rf value increased from the beginning to the end of the experiment indicates the occurance of the reaction since the product dibenzalacetone is less polar than the reactants acetone and benzaldehyde.
Repeat 3 times. Stir the reaction for 15 minutes with the flask open to air. Prepare to wash and dry the solid. Rinse the solid with 5—8 drops of ethanol. However, the aldol reaction is not formally a condensation reaction because it does not involve the loss of a small molecule Smith,
Thus at higher temperature in base the aldol reaction will go directly to the conjugated enone without any isolation of the aldol intermediate. In every case, the product results from the addition of one molecule of an aldehyde or ketone to a second molecule in such a way that the a-carbon of the first becomes attached to the carbonyl carbon of the second. Explain your answer. Draw a complete electronic mechanism of the aldol product between benzaldehyde and acetophenone.
Allow the solution to cool slowly to room temperature and then cool in an ice bath.