The Cannizaro reaction is a self-oxidation and self-reduction reaction between two molecules of an aldehyde in the presence of an aqueous or alcoholic base such as NaOH or KOH. This redox reaction produces a primary alcohol through reduction of one aldehyde and a carboxylic acid salt through oxidation of the other aldehyde molecule. The reaction involves a nucleophilic acyl substitution on an aldehyde carbonyl group by hydroxide, followed by hydride transfer between two aldehyde molecules to form the alcohol and carboxylic acid salt products.

1. Cannizaro reaction
Prepared by: Nidhi Ghetiya

2. Introduction
• The cannizaro reaction was discovered by stanislao cannizzaro.
• It is generally occurs in aldehyde that not having a α- Hydrogen.
• Thais is a self oxidation and self reduction reaction.
• In this reaction 2 molecules of aldehyde are reacted to produce a
primary alcohol and carboxylic acid salt.
• The reaction occurs in the presence of aqueous or alcoholic
NaOH or KOH.

3. • In this reaction the oxidation product is a salt of carboxylic
acid and the reduction product is alcohol.
• So it is a redox reaction.

4. Reaction
2HCHO + NaOH CH3OH + HCOONa
Formaldehyde Alcohol Sodium salt of
carboxylic acid
+ NaOH +
Benzaldehyde Benzyl alcohol Sodium Benzoate
HOH2C NaOOCO H C

5. Mechanism
• The reaction involves a nucleophilic acyl substitution on an aldehyde
while the leaving group attacks another aldehyde in the next step.
• Step:1 Hydroxide attacks a carbonyl group to form an anion.
C
H O
O H C
O H
O H
+

6. • Step 2: Anion transfers a hydride ion to a second aldehyde molecule
• Step 3: Addition and removal of hydride ions take place to form salt of
carboxylic acid and alcohol.
C 6H 5 C
O
H
C 6H 5 C
O
O H
C 6H 5 C
O H
O
+H C 6H 5 C
O
H
H+
C6H5 C
O
H
H C6H5CH2OH
H

7. Crossed Cannizaro Reaction
• Cannizaro reaction takes place between two different aldehydes having no
α-hydrogen is known as crossed cannizaro reaction.
• Four different products are formed.
Benzaldehyde Formaldehyde Benzyl alcohol Sodium Salt
CHO
+ HCHO + NaOH
CH2OH
+ HCOONa

8. Application
• Benzyl alcohol is obtained by crossed cannizaro reaction.
• O-methoxybenzyl alcohol is prepared by the cannizaro reaction.