Mechanisms of Baeyer Villiger Oxidation of Ketones, Cannizzaro Reaction, MPV

1. CHEMISTRY
-ADITYA ARYA
B.SC.B.ED (CBZ)
Baeyer – Villiger
Oxidation of Ketones
Cannizzaro Reaction
MPV

2. Baeyer - Villiger
Oxidation of Ketones
Oxidation of ketones with peroxy acids
gives esters by a novel rearrangement.

3. R"COOH
O
RCR'
O
+ R"COH
O
+
Ketone Ester
ROCR'
O
GENERAL REACTION :

4. C6H5COOH
O
(67%)
 Oxygen insertion occurs between carbonyl carbon
and larger group.
 Methyl ketones give acetate esters.
CHCl3
CCH3
O
OCCH3
O
EXAMPLE :

5. C6H5COOH
O
(66%)
STEREOCHEMISTRY :
 Reaction is stereospecific.
 Oxygen insertion occurs with retention of
configuration.
CHCl3
O
CCH3H3C
H H
OCCH3
O
H3C
H H

6. R"COOH
O
RCR'
O
+ ROCR'
O
R"COH
O
+
MECHANISM :

7. R"COOH
O
RCR'
O
+ ROCR'
O
R"COH
O
+
O
O
C
O H
R R'
OCR"
First step is nucleophilic
addition of peroxy acid
to the carbonyl group of
the ketone.
MECHANISM :

8. R"COOH
O
RCR'
O
+ ROCR'
O
R"COH
O
+
O
O
C
O H
R R'
OCR"
Second step is migration
of group R from carbon
to oxygen. The weak
O—O bond breaks in this
step.
MECHANISM :

9. CANNIZZARO
REACTION
Cannizzaro reaction is a chemical
reaction named after Stanislao Cannizzaro
that involves the base-induced
disproportionation of two molecules of a
non-enolizable aldehyde to yield a
carboxylic acid and a primary alcohol

10. Cannizzaro Reaction Mechanism details the method to get
one molecule of alcohol and one molecule of carboxylic
acid from two molecules of a given aldehyde.
Scientist Stanislao Cannizzaro, in 1853 succeeded in
obtaining benzyl alcohol and potassium benzoate from
benzaldehyde.
 The reaction is executed by a nucleophilic acyl
substitution on an aldehyde where the leaving group attacks
another aldehyde.

11. A tetrahedral intermediate results from the attack of
hydroxide on a carbonyl.
This tetrahedral intermediate collapses, thereby
reforming the carbonyl and transferring a hydride which
attacks another colony.
Now, a proton is exchanged by acid and alkoxide ions. When
a base of high concentration is introduced, the aldehyde forms
an anion which has a charge of 2. From this, a hydride ion is
transferred to a second molecule of the aldehyde, forming
carboxylate and alkoxide ions. The alkoxide ion also obtains a
proton from the solvent for the reaction.

12. Mechanism of Cannizzaro Reaction
Mechanism Step 1:
A nucleophile such as a hydroxide ion is used to
attack the carbonyl group of the given aldehyde,
causing a disproportionation reaction and giving
rise to an anion carrying 2 negative charges.

13. This resulting intermediate can now function as a hydride
reducing agent. Due to its unstable nature, the intermediate
releases a hydride anion. This hydride anion proceeds to attack
another aldehyde molecule. Now, the doubly charged anion is
converted into a carboxylate anion and the aldehyde is converted
into an alkoxide anion.
Mechanism Step 2:

14. Mechanism Step 3:
In this final step, water offers a proton to the alkoxide anion which
gives rise to the final alcohol product. The reaction can proceed since
the alkoxide is more basic than water. Now, the carboxylate ion gives
rise to the final carboxylic acid product when acid workup is used (the
acid workup is required since carboxylate is less basic than water and
therefore cannot obtain a proton from water).

15. MEERWEIN-PONNDORF-VERLEY
REDUCTION (MPV)
• MPV reduction is the reduction of aldehyde and ketones to their
corresponding alcohols utilizing Aluminium oxide catalysis in the
presence of sacrificial alcohol.
• MPV reduction was discovered by Meerwein and Schmidt and
separated by Verley in 1925.They found that the mixture of
aluminium oxide and ethanol could reduce aldehyde to alcohols.
• Pondroff applied the reaction to ketones and upgraded the catalyst to
aluminium isopropoxide in isopropanol.

16.  Conversion of aldehyde or ketone in to corresponding
alcohol by treatment with Aluminium isopropoxide in
isopropanol solution.
 This reaction is reversible and is called Oppenauer
oxidation.
GENERAL REACTION :

17. MECHANISM :

19. This method of reduction is specific for carbonyl group
and therefore it can be used for reducing aldehydes and
ketones containing some other reducible group, such as, a
double bond, a nitro or an ester group, which are not
reduced under these conditions
APPLICATIONS :

21. Used in synthesis of oestradiol