Volume: 3 Issue: 1 Pages: 04-08
International Journal of Advance
Studies and Growth Evaluation
Comparative Study of Various Methods of Performing Cannizzaro Reaction
and Calculating the Final Yield
*1
MR Chaya, 2Manoj SV, 3Rekhashree H and 4Pranav R Rao
*1
Associate Professor, Department of Chemistry, KLE’s S Nijalingappa College, Bengaluru City University, Karnataka, India.
2,3Assistant Professor, Department of Chemistry, KLE’s S Nijalingappa College, Bengaluru City University, Karnataka, India.
4 Research Scholar, Department of Chemistry, KLE’s S Nijalingappa College, Bengaluru City University, Karnataka, India.
Article Info. Abstract
E-ISSN: 2583-6528 The most often employed reaction in organic synthesis is Cannizzaro's reaction. Cannizzaro's
response appears to be highly well-liked by the various universities due to its unique
Impact Factor (SJIF): 5.231
qualities. It can be carried out on a large or small scale and is covered in a variety of books
Peer Reviewed Journal and articles on organic synthesis.In the presence of a base, the aldehyde functional group
Available online: without alpha hydrogen is transformed into carboxylic acid and alcohol. A study was carried
www.alladvancejournal.com out wherein three distinct experimental procedures were utilized to produce benzoic acid and
benzoyl alcohol from the reaction between benzaldehyde and a strong base such as
Received: 15/Dec/2023
potassium hydroxide or sodium hydroxide. This report presents a comparative analysis of the
Accepted: 05/Jan/2024
total yield produced through three distinct experimental procedures. Mechanical stirring is
the first technique, the second involves a hot water bath, and the third involves grinding.
These techniques were also tested with two distinct concentrations of the same .The yields of
products using two bases and three distinct processes were tallied and compared. When
alcoholic sodium hydroxide was utilized as the base in the grinding process, the yield of the
products increased; however, in the other two techniques that also used alcoholic sodium
hydroxide, the yield of benzoic acid and benzyl alcohol was significantly lower.TLC and IR
*Corresponding Author data are used to characterize every product that is obtained.
MR Chaya
Associate Professor, Department of
Chemistry, KLE’s S Nijalingappa
College, Bengaluru City University, Keywords: Benzoic acid, benzyl alcohol, base, benzaldehyde, nucleophilic substitution.
Karnataka, India.
Introduction methods performed mechanical stirring method is the widely
Benzoic acid and Benzyl alcohol is an organic product formed used method for the performance of Cannizzaro’s reaction.
when there is a reaction between Benzaldehyde and a Strong The other two methods are rarely used in the performance of
base like sodium hydroxide and potassium hydroxide. This the reaction. The main aim of the experiment was to calculate
reaction is called the Cannizzaro’s reaction. The Cannizzaro the percentage of the final yield obtained during all the three
reaction is a reaction that occurs in the compounds containing methods and to compare them.
aldehyde group. The main criteria of the reaction are the In continuation of our interest, the current work represents the
absence of the alpha hydrogen. Aldehydes with alpha comparative study of the final yield obtained during the three
hydrogen are very easily prone to enolization and then aldol methods of performing the Cannizzaro’s reaction.
condensation. If there are no alpha hydrogen atoms, there can
be no enolate formation and thus no aldol. The only Reaction Scheme
possibility is nucleophilic attack on the aldehyde carbonyl
group. When the aldehyde is made to react with the base like
sodium hydroxide or potassium hydroxide there is an alcohol
and a carboxylic acid formed as the product.
Benzoic acid and Benzyl alcohol have been synthesised from
Benzaldehyde by three different methods. Among the three Benz aldehyde Benzoic acid Benzyl alcohol
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International Journal of Advance Studies and Growth Evaluation https://alladvancejournal.com/
Materials and Methods 2. Heating on Water Bath
The AR grade chemicals used to perform the reaction are The same reaction is carried out in a water bath. The water
benzaldehyde, sodium hydroxide, potassium hydroxide, ethyl bath heating method includes the heating of the reactants for
acetate for separation of the products, sodium chloride for the specific amount of time.
clear separation, and conc. Hydrochloric acid for extraction of A) The reactants include Benzaldehyde and alcoholic
product. potassium hydroxide. Alcoholic potassium hydroxide is
prepared by dissolving 2.2g of potassium hydroxide pellets in
The Different Methods Employed for the Comparative some amount of ethanol. Then to the alcoholic potassium
Study of Cannizzaro's Reaction are Discussed Below hydroxide and 2ml of Benzaldehyde is mixed together and
1. Mechanical Stirring Method kept in a water bath and stirred periodically. After 8-10
This is the widely used method for the preparation of benzoic minutes the mixture becomes a fine solid paste like substance.
acidandbenzyl alcohol from benzaldehyde. The mechanical The fine solid paste of Benzaldehyde and alcoholic potassium
stirring method includes the stirring of the reactants for a hydroxide is then transferred into a separating funnel. The
specific amount of time. The reactants include benzaldehyde separating funnel with the mixture is added with 20ml of ethyl
and base. acetate and sodium chloride for the clear separation of
A) In the first case, alcoholic potassium hydroxide is used as aqueous and organic layer. The separating funnel is left idle
a base of approximately 0.04 moles (prepared by dissolving for 5-10 minutes and then aqueous and organic layer are
2.2g of potassium hydroxide pellets in ethanol). The prepared separated put into different beakers. The beaker containing
alcoholic potassium hydroxide and 2ml of benzaldehyde is the aqueous layer is added with concentrated Hydrochloric
stirred continuously for one hour till the liquid products turn acid till the pH of the solution turns acidic thus the precipitate
into a fine paste. The obtained paste is then taken in a formed by adding the concentrated Hydrochloric acid is the
separating funnel and ethyl acetate is added to which few crude benzoic acid.
drops of sodium chloride solution is added for the clear The crude benzoic acid precipitate is filtered out using the
separation of organic and aqueous layer. To the obtained filter paper and then allowed to dry. The dried crude crystals
aqueous layer cconcentratedHydrochloric acid is added till the are then recrystallized by dissolving them with small amount
pH of the solution turns acidic. The Precipitate thus formed is of ethanol and heating them in a water bath to remove the
then filtered using a filter paper and then dried. The dried impurities. The solution is then filtered into a watch glass and
precipitate is then recrystallized using alcohol to obtain a fine allowed to cool. After cooling the needle like structures
needle like crystals of benzoic acid. To the organic layer, a formed is the benzoic acid. The other beaker containing the
pinch of anhydrous sodium sulphate crystalsare added to organic layer is treated with sodium sulphate crystals to
remove the moisture content in the organic layer, filtered and remove the excess moisture content. Then the solution is
heated in a water bath to evaporate ethyl acetate, after few filtered into another beaker the solution is then heated to 6-8
minutes the oily layer of benzyl alcohol is obtained. minutes to remove the ethyl acetate content. After all the ethyl
The melting point of products is determined to confirm the acetate is evaporated the oily layer left out in the beaker is the
product formation, TLC and IR Spectrum is recorded for Benzyl alcohol. The melting points of the obtained yields are
confirmation of product formation. determined. The obtained yield is verified using the TLC and
B) In the second case, alcoholic sodium hydroxide is used as IR Spectrum.
base instead of potassium hydroxide for the above procedure, B) In the second case, alcoholic sodium hydroxide is used as
to compare the yield of the products in different bases used. base instead of potassium hydroxide for the above procedure,
to compare the yield of the products in different bases used.
Mechanical Stirring Method Separation
Heating on Water Bath Separation
Benzoic Acid Benzyl Alcohol TLC
Benzoic Acid Benzyl Alcohol TLC
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International Journal of Advance Studies and Growth Evaluation https://alladvancejournal.com/
3. By Grinding Method Benzyl alcohol. The melting point of the obtained yield is
Grinding method is the method of preparing the benzoic acid determined. The products are verified using the TLC and IR
and benzyl alcohol in a unique way. The reagents are ground spectrum.
in a mortar using a pestle. The method involves grinding the B) In the second case, alcoholic sodium hydroxide is used as
reagents for about 45-60 minutes. base instead of potassium hydroxide for the above procedure,
A) The reagents include benzaldehyde and potassium to compare the yield of the products in different bases used.
hydroxide. About 1.5 grams of potassium hydroxide was
taken in the mortar and about 2ml of benzaldehyde was added
into it, the mixture was finely ground for about 1 hour. The
solid paste that was obtained was then transferred to a
separating funnel and then it is added with ethyl acetate and
then with sodium chloride solution for the clear separation
then the separating funnel is left idle for about 5-10 minutes
then the aqueous layer and organic layer is separated into two
separate beakers. The beaker containing the aqueous layer is
added with concentrated hydrochloric acid till the pH of the
solution turns acidic thus the precipitate formed by adding the
Grinding Method Separation
concentrated hydrochloric acid is the crude benzoic acid.
The crude benzoic acid precipitate is filtered out using the
filter paper and then allowed to dry. The dried crude crystals
are then recrystallized by dissolving them with small amount
of ethanol and heating them in a water bath to remove the
impurities. The solution is then filtered into a watch glass and
allowed to cool. After cooling the needle like structures
formed is the benzoic acid. The other beaker containing the
organic layer is treated with sodium sulphate crystals to
remove the excess moisture content. Then the solution is
filtered into another beaker the solution is then heated to 6-8 Benzoic Acid Benzyl Alcohol TLC
minutes to remove the ethyl acetate content. After all the ethyl
acetate is evaporated the oily layer left out in the beaker is the
IR Spectrum of the Products
A) Benzoic ACID
Fig 1: IR Spectrum of Benzoic Acid
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International Journal of Advance Studies and Growth Evaluation https://alladvancejournal.com/
B) Benzyl Alcohol
Fig 2: IR Spectrum of Benzyl Alcohol
Results and Discussion
Table 1: Comparison of Practical and Percentage Yield of Products Obtained from Three Different Method
Practical Yield of Practical Yield of Percentage Yield of Percentage Yield of
Method
Benzoic Acid Benzyl Alcohol Benzoic Acid Benzyl Alcohol
Mechanical Stirring A) 0.65g A) 0.62mL A) 75.58% A) 61.38%
Method B) 0.43g B) 0.45mL B) 50.00% B) 44.55%
A) 0.56g A) 0.56mL A) 65.11% A) 55.44%
Heating on a water bath
B) 0.32g B) 0.43mL B) 37.20% B) 42.57%
A)0.48g A) 0.56mL A) 55.81% A) 55.44%
Grinding method
B) 0.22g B) 0.76mL B) 26.58% B) 75.24%
The above mentioned three methods are the commonly used calculations using their molecular weights. The practical yield
convenient methods to prepare the Benzoic acid and benzyl and percentage yield of both the products are tabulated as
alcohol from benzaldehyde. The yield obtained by these three below,
methods is compared to the theoretical yield obtained by
Fig 3: Representation of product yield in three methods using KOH base
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International Journal of Advance Studies and Growth Evaluation https://alladvancejournal.com/
Fig 4: Representation of product yield in three methods using NaOH base
Conclusion
The comparative study of yield of benzoic acid and benzyl
alcohol obtained from benzaldehyde through Cannizaro’s
reaction using three different methods and two different bases
gives a positive result. Among the methods followed, the first
method, that is mechanical stirring method gives a good yield
of both benzoic acid and benzyl alcohol when alcoholic
potassium hydroxide is used as a base. The yield of both the
products were more when alcoholic sodium hydroxide was
used as base under grinding method, but in other two methods
using alcoholic sodium hydroxide the yield of both benzoic
acid and benzyl alcohol was considerably less. From the
above data obtained it can be concluded that the mechanical
stirring method is the most convenient method for obtaining
high yield of the products and among bases used alcoholic
potassium hydroxide gives good yield when compared to the
use of sodium hydroxide as a base.
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