CHEM101 Lab: Synthesis of Benzalacetophenone via Claisen-Schmidt

This assignment details the experimental procedure for synthesizing benzalacetophenone through the Claisen-Schmidt reaction, an aldol condensation. The report outlines the objectives, which include preparing benzalacetophenone from acetophenone and benzaldehyde, and observing the effects of different catalysts. The introduction explains the reaction's mechanism, emphasizing the importance of C-C bond formation and the role of acid or base catalysts. The materials and methods section describes the preparation of trans-benzalacetophenone using sodium hydroxide, ethanol, acetophenone, and benzaldehyde, including crystallization and recrystallization steps. The reaction of benzalacetophenone with bromine is also detailed. The results section presents the weight and melting point of the product, along with potential sources of error. The conclusion suggests that the base catalyst led to a higher yield and potentially lower melting point due to impurities. This assignment provides a comprehensive overview of the Claisen-Schmidt reaction, covering experimental procedures, results, and analysis.

Title: CLAISEN-SCHMIDT REACTION- THE PREPARATION OF
BENZALACETOPHENONE
(b) Objectives
 To prepare benzalacetophenone from atophenone tn aldehyde and accetophenone through
Claisen-Schmidt reaction
 Show how different catalysts affect the Claisen-Schmidt reaction
(c) Introduction and background
This experiment is based on aldol condensation reaction. This is because the process involves
self-addition of two aldehydes or ketones. The end result from this reaction forms C-C bond that
is able to connect the carbonyl carbon of the first molecule to the α-carbon end in the second
molecule. The process is like combining the reactants to form a single product. In this reaction,
the part of the reaction must be reactive with the carbonyl part and be able to react with acidic
hydrogen to ensure that the product will be formed. The following reaction describes the
reaction which takes place when the reactants are mixed. Moreover this reaction can be speed up
by introducing an acid or a base as catalysts.
Using base and acid catalysts is able to lead to different reactions. The following sections will
analyze the results which are achieved. Moreover, this reaction is able to occur directly through
an enolate intermediate. Water elimination is at sometimes able to occur in a mild condition in
order to form respective unsaturated products. The condensation reaction using base as a
catalysts results to the following results;

In addition, acid catalysts are also used in the speeding up of the condensation reaction. Under
this catalyst, the reaction is able to occur through enol intermediate. The following presents the
reaction which takes place when the acid catalyst is used in the reaction;

Generally, the reaction between an aldehyde and acetophene through the Claisen-Schmidt
reaction lead to production of benzalacetophenone of simply chalcone. As noted, C=C bond is
essential to form the unsaturated ketone. The following reaction is able to represent the reaction;
(d) Material and Methods List the chemicals, apparatus and equipment used.
1. First prepare the trans-Benzalacetophenone. To prepare it, place 10% of aqueous sodium
hydroxide, 15 ml ethanol and 6g of 0.05M acetophenone in a flask.
2. Ice-cool bath the mixture and shake it.
3. Add 5.3g, 5ml 0.05M benzaldehyde. Wait for the temperature to rise to room temperature.
4. Shake vigorously from time to time for one hour until yellow oil forms on the flask. Place the
flask on refrigerator for further crystallization.
5. Wait until the yellow oil solidifies. Scratch the crystals from the flask and filter through
vacuum filtration and neutralize the crystals by washing with 5ml of cold ethanol.
6. Then keep the crystals and do recrystallization with hot ethanol. Shake the flask on ice-bath
and collect product through vacuum filtration.
7. Dry and record the weight of the results. Also measure the melting point of the product.
Reaction of Benzalacetophene
1. dissolve 1.0g of trans-benzalacetophenone in 4 ml of tetrachloromethane.
2. 2. Add 4ml of bromine on the tetrachloromethane.
3. 3. Cool the solution in ice bath and add bromine in tetrachloromethane using a pipette
while swirling the flask
4. Let the mixture settle for five to ten minutes.
5. Collect the crystals through vacuum filtration

6. Wash the crystals with little 95% ethanol. Allow the crystals to dry and measure the
weight and MP.
(e) Results and Discussion
A
Weight of product = 7.1g
Melting point = 45oC – 550C
B
Weight of product = 2.21g
Melting point = 110oC-120oC
Assumption
Correct value of solution was added.
Errors
Errors human error in reading weight and MP
Human error in adding solutions
(f) Conclusions
The results were able to indicate that the solution prepared with base was able to lead to higher
weight. The base was therefore a key contributor to the formation of the crystal and therefore
forming the high weight. In addition, the solution had low MP. The base may have contributed to
the lowering of the MP of the crystal since they are impurities.
The aldol condensation does not have impurities and therefore it is considered to be the main
reaction on the experiment. In addition, it has the main component which form the solution and
therefore main in experiment.