procedure: For this experiment, I will put 1.05g of benzyl and 1.05g dibenzyl ke
ID: 520744 • Letter: P
Question
procedure:
For this experiment, I will put 1.05g of benzyl and 1.05g dibenzyl ketone into a 100ml round bottom flask. I will also add 20ml ethanol, and .23g potassium hydroxide pellets plus a stir bar. Set up a reflux condenser and boil the solution for 15 minutes. The solution should turn into a purple color. That’s how you know the product is forming. Stir it periodically while heating it. Cool the mixture to room temperature and then put it in an ice bath. Put the mixture in a Buchner funnel and wash it with 10ml water. Then wash with 10ml cold ethanol. Let the product air dry and find the yield and the melting point.
benzil+dibenzil ketone--->tetraphenylcyclopentadienone
What is a condensation reaction? What is the small molecule lost in this reaction?
In this reaction, all the reactants are ketone compounds. Can condensation reactions be extended to other carbonyl compounds than ketones?
What is an enol? In a tautomerization equilibrium, will the enol or the keto isomer will be favored?
What is the driving force for the enolization? (what causes the enolate ion to be formed?)
The reaction goes through color change. Why the color change happens in this reaction and how can this information is associated with the (predicted) success of this reaction?
Which technique is better for the analysis of your reaction, the IR or the 1H NMR?
Calculations: Use the amount of Benzil and dibenzyl ketone to determine how much of tetraphenylcyclopentadienone are expected to obtain. Then, using the mass for your product, calculate the % yield for the reaction
Explanation / Answer
Explanation:
A)1)Reaction between dibenzyl ketone with benzil in presence of potassium hydroxide is Claisen Schmidt condensation which is the carbanion addition reaction to carbonyl group.
2)Shall molecule that is lossed in the reaction is water
3)This condensation reaction can be extended to dialdehydes & diesters .
B)1)Enols are alpha-beta unsaturated hydroxy compounds and are hydroxy analogues of enamines
2)In taumerization equilibrium an enol form is favoured .
3)The driving force for enolization is the formation of hydrogen bonding in enol
4)The enolate ion is formed due to acidic nature of the hydrogen
C)1)The reaction passes through the colour change a due to the formation of fully extended conjugated system as a product of the reaction. & one can measure the color intensity by colorimetry using Beer-Lambert law.(Analytical application)
2)1H NMR is useful technique to for the analysis of the reaction as benzylic protons is dibenzyl ketone are disappearing & in the product, only aromatic protons are seen in the NMR spectrum.
D)The yield of the reaction is 1.92 g. taking into account benzil. One can calculate % yield when practical yield (observed yield)is given.
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