1) The Cannizaro reaction involves the disproportionation of benzaldehyde to benzoic acid and benzyl alcohol in the presence of sodium hydroxide without the use of solvents. 2) Benzaldehyde and sodium hydroxide were ground together for 30 minutes, then water was added and acidified with hydrochloric acid to precipitate benzoic acid. 3) The filtrate was extracted with ethyl acetate and evaporated to obtain benzyl alcohol, completing the Cannizaro reaction of benzaldehyde to its corresponding carboxylic acid and alcohol products.

1. Cannizaro’s Reaction:
Benzaldehyde
by
solvent free grindstone
technique

2. The disproportionation reaction (self oxidation and reduction) of
non enolizable aldehydes to corresponding carboxylic acid and
alcohol in presence of base is known as Cannizaro’s reaction.
In this experiment benzaldehyde underwent solvent free
disproprtionation reaction to benzoic acid and benzyl alcohol in
presence of sodium hydroxide.
PRINCIPLE:

3. 1) Benzaldehyde
2) NaOH
3) Ethyl acetate
4) Na2SO4
5) HCl
CHEMICALS REQUIRED: APPARATUS:
1) Mortar and pestle
2) Beaker
3) Separating funnel
4) Funnel
5) Measuring cylinder
6) Filter paper

4. REACTION:
H
O
OH
O
2
OHNaOH
Grind, 30 min
Lab Temp.
H3O+

5. PROCEDURE:
•1 g Benzaldehyde (0.0096 mol) was taken in a clean and dry
mortar. To this 0.75 g NaOH (0.0188 mol) was added and
grounded well together using pestle for 30 minutes at lab
temperature. The reaction proceeds exothermically.
Paste at the beginning
of the grinding
O H
NaOH

6. •After 30 minutes of grinding (indicated by no smell of
benzaldehyde), pour 15 ml of cold water into the whole reaction
mass and neutralize the mixture with concentrated HCl till acidic
pH. The precipitated product (benzoic acid) was collected by
filtration and dried.
ONa
O
OH
Pour water and add HCl till
acidic to pH
Collect the precipitate by
filtration

7. •The filtrate was extracted to 20 ml of organic layer (ethyl
acetate) and dried over anhydrous Na2SO4. The organic layer was
evaporated and benzyl alcohol was obtained.
Filtrate was extracted
to 20 ml of organic
layer (ethyl acetate)
Dried over
anhydrous
Na2SO4
The organic
layer was
evaporated and
benzyl alcohol
was obtained
Ethyl acetate
Na2SO4

8. MECHANISM:
H
O
OH
H
O
OH
H
O
OH
O
O
H H
O
O
OH
H H
OH
O
Hydride shift
Proton transfer
H3O

9. Benzaldehyde: Bitter almond
Benzoic acid: Slight pungent
Benzyl alcohol: Odourless
CHEMICAL TESTS:
Odour
Benzaldehyde: No evolution of gas (-Ve)
Benzoic acid: Evolution of gas (+Ve)
Reaction with NaHCO3
Benzaldehyde: Orange precipitate (+Ve)
Benzyl alcohol: No Orange precipitate (-Ve)
Reaction with 2,4-DNP

10. THANK YOU
Arabian journal of chemistry, 2016, 9, S1373-S1377.
REFERENCES: