Spectroscopy is the study of the interaction of electromagnetic radiation with matter. There are many forms of spectroscopy, each contributing useful information to identify substances and to determine various characteristics of their structure.
Synthesis of Dibenzalacetone by Aldol Condensation Objective: To carry out a mixed aldol condensation reaction 2.
To study the mechanism of aldol condensation reaction Introduction: The reaction of an aldehyde with a ketone employing sodium hydroxide as the base is an example of a mixed aldol condensation reaction, the Claisen-Schmidt reaction. The double mixed-aldol condensation reaction between acetone and benzaldehyde was carried out.
The elimination process is particularly fast in this case because the alkene is stabilized by conjugation to not only the carbonyl but also the benzene.
In this experiment, excess benzaldehyde such that the aldol condensation can occur on both sides of the ketone.
Dibenzalacetone is readily prepared by condensation of acetone with two equivalent of benzaldehyde. Depending on the relative quantities of the reactants, the reaction can give either mono- or dibenzalacetone.
Dibenzalacetone is a fairly innocuous substance in which its spectral properties indicate why it is used in sun-protection preparations.
In the present experiment, sufficient ethanol is present as solvent to readily dissolve the starting material, benzaldehyde and also the intermediate, benzalacetone.
The benzalacetone once formed, can then easily to react with another mole of benzaldehyde to give the desired product in this experiment, dibenzalacetone. After 15 minutes of occasional swirling, the products was filtered on a Buchner funnel.
The product was washed with cold ethanol and was allowed to suck dry. The yellowish product was recrystallized from ethyl acetate.
After recrystallization, a yellow crystalline was obtained. The weight, yield, and melting point of the product were determined.
The UV and IR spectra of dibenzalacetone were ontained. Condensation is a process which joins two or more molecules usually with the loss of a small molecule such as water or an alcohol. The product is also known as adol because it containing two functional groups which includes aldehyde or ketone group and alcohol group.
The product dibenzalacetone was formed from the reaction between an acetone molecule and two benzaldehyde molecules. Generally, the aldol condensation is carried out under a base condition.
Sodium hydroxide was mixed with distilled water then was used to react with sufficient ethanol as the first step.
The particular reaction is an exothermic reaction which released the heat energy to the surrounding from the reaction. The sodium hydroxide was functioned as a catalyst in the reaction. The ethanol acts as a solvent which allows the acetone and benzaldehyde to dissolve and react with each other. After that, acetone and benzaldehyde were mixed in the solvent which turns to yellow colour quickly.
Eventually, the product was formed with a yellow precipitate appear in the reaction after a few seconds. However, there are some impurities and side products were formed in the yellow precipitate.
So, recrystallization was carried out by using ethyl acetate as solvent in order to purify the product and hence a pure product could be obtained for the ultraviolet UV and IR spectra analysis. In the recrystallization process, the yellow precipitate in ethyl acetate was immersed into an ice-bath in order to obtain a higher yield of product.
This is because the heat energy in the precipitate easily to be released since the precipitation formation is an exothermic reaction and hence it maximizes the formation rate of the product. Acetone is considered as a stable and unreactive compound, so it should be converted into anionic form to increase its nucleophile properties to initiate the reaction.
The deprotonation of acetone caused the enolate ion was produced as nucleophile which will be used in the synthesis of dibenzalacetone. An enolate ion was formed which it exists as resonance-stabilized structure which shown in the following diagram: Diagram 1 The acetaldehyde enolate ion attack to the benzylic carbon of benzaldehyde via nucleophilic addition to form the intermediate as shown in below: Diagram 2 The oxygen attached to the benzylic position of carbon tends to attract one proton from water molecule to form hydroxide group in the intermediate.
This is the formation of an aldol since the molecule consists of a carbonyl group and an alcohol group. After the condensation, benzalacetone was formed after two water molecules leaved as shown: Diagram 3 The benzalacetone tends to form benzalacetone enolate ion after the hydroxide group from the surrounding attack the proton which attached to the carbon at benzylic position.
Diagram 4 The same process has been take place as in the Diagram 2 but with the more bulky benzalacetone enolate ion as the material.Perhaps the most important step is waiting for the hot solution to cool slowly and allow crystals to form.
It is extremely important to be patient and allow the solution to cool undisturbed.
If too much solvent is added so that little crystals are formed upon cooling, evaporate some of . Sep 12, · INKJET PRINTING METHODS AND INK SETS characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.
A back-pressure regulation mechanisms in the form of pressure buffers or. This shows the mechanism of the experiment performed.
The reaction proceeds by an aldol condensation. Step 1: First, an acid-base reaction. Hydroxide functions as a base and removes the acidic α-hydrogen giving the reactive enolate.
Write the full mechanisms for SN1 and SN2 reactions. Draw concise and detailed energy reaction diagrams for reactions considered. Describe physical properties of alcohols on the basis of molecular structure. Discuss methods of preparation of alcohols.
Synthesis of Dibenzalacetone. This reaction is beginning. Theoretical yield of dibenzalacetone mol. 1 mol 1. Check answers to questions Questions 1 A Write a detailed mechanism for the formation of benzalacetone - See above in the mechanism section for full detailed mechanism.
B Give. ALDOL SYNTHESIS of DIBENZALACETONE, AN ORGANIC SCREEN. The Project Gutenberg EBook of Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 2, by Various This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever.
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