Report Record the yield, color and melting point of the purified benzil. If you have not already done so last week , weigh the benzoin crystals from last weeks experiment. Check with your instructor to see if this is required. An impurity of ethanol appeared at 4. DO NOT remove the reaction mixture from the hood until the instructions indicate that you should do so. IR w , s cm
The solid was transferred to a mL flask of hot water 60 mL and mixed until completely dissolved. If you are NOT going to perform the recrystallization - Remove the product from the filter paper and dry it in the oven for about 10 minutes. After the 10 minute heating period, slowly add 75 mL of water to the reaction mixture, cool to room temperature, and swirl for a minute or two to coagulate the precipitated product; make sure that there are no nitrogen oxide fumes remaining in the flask. You will also see the formation of dark orange or brown NO fumes as the reaction proceeds.
The ultimate products of ylide and benzoin are produced. Results and Discussion For the first reaction, the presence of crystals after the combination of the ylide and benzaldehyde appeared pale yellow, solid but mushy. It is best to perform this reaction in a mL Erlenmeyer flask, to minimize the possibility of splattering. Finally, a peak at Advantages imply the production of ideal, marketable end products, and the synthesis of compounds that otherwise could not be produced through a simple reaction. The 13C NMR spectra displayed a weak peak at
Once the solution is basic, cool the mixture in an ice bath for a few minutes. A peak did not appear at 12 ppm that would have represented the hydrogen of the carboxylic group, which means the reaction was not carried to completion. Cleaning Up The aqueous filtrate is non-toxic, and should be neutral or slightly basic. In this reaction, the two aldehydes serve different purposes; one aldehyde donates a proton and one aldehyde accepts a proton. Caution: Concentrated nitric acid is corrosive! This corresponds to the melting point of the crude product concluding that purification failed.
A peak at 5. Caution: Concentrated nitric acid is corrosive! The reaction mechanism was proposed in by A. Once the solution is basic, cool the mixture in an ice bath for a few minutes. Report Record the yield, color and melting point of the purified benzil.
This is your product, but it may not solidify in acid solution.
The final mechanism, shown in scheme 3, involves the synthesis of the carboxylate salt intermediate, potassium benzilate, which drives the reaction to produce benzilic acid through workup. In the 13C-NMR spectrum for benzil, how many signals would you expect to see? Note: At this point you may notice one or more globules of an oily substance in your flask.