B.Sc II Sem III Chemistry College Name :- Late Ku.Durga K.Banmeru Science College Lonar University Name:- Sant Gadgebaba Amravati University Amravati

1. 1
Late Ku. Durga K. Banmeru Science College,
LONAR DIST. BULDANA (Maharashtra), India.
Aldehydes and Ketones”
Mr.Shivshankar Purushottam More
Head Of Department
Department of Chemistry
Late Ku. Durga K. Banmeru Science College, Lonar
B. Sc. IInd year Sem-IIIrd Subject:- Chemistry
Chapter- III

2. Reactions of Aldehydes and or Ketones
1. Cannizzaro Reaction
Defn- The reaction in which aliphatic or aromatic aldehydes do not
containing -hydrogen, when heated with concentrated alkali, undergo
a disproportion reaction to form sodium salt and alcohol this reaction
is called as Cannizzaro Reaction.
 This reaction given by Italian Chemist Stanisalo Cannizzaro in
1883, hence this reaction is called as Cannizzaro Reaction
 Condition of reaction-
Aldehyde which do not have -hydrogen atom gives this reaction
50% NaOH (alkali) solution is must for this reaction.
2

3. Examples- Formaldehyde and Benzaldehyde which do not have -
hydrogen atom gives this reaction
H C H
O
H C H
O
+
50% NaOH

H C O
O
Na C
H3 OH
+
Formaldehyde
SodiumFormate Methyl Alcohol
1. When formaldehyde heated with 50% NaOH solution, one molecule
is oxidized to sodium formate whereas other molecule is reduced to
methyl alcohol.
2. When bezaldehyde heated with 50% NaOH solution, one molecule
is oxidized to sodium benzoate whereas other molecule is reduced to
benzyl alcohol.
50% NaOH

+
H
O
H
O
O
O
Na
OH
O
+
Benzaldehyde SodiumBonzoate Benzoic acid
3

4. Defn-The reaction in which two different aldehydes do not containing -
hydrogen, when heated with concentrated alkali is called as Cannizzaro
Reaction.
Cross Cannizzaro Reaction-
1. When formaldehyde benzaldehyde heated with 50% NaOH solution,
formaldehyde is oxidized to sodium formate whereas benzaldehyde
is reduced to benzyl alcohol.
H
O
H C H
O
+
50%NaOH

H C O
O
Na +
OH
Formaldehyde Bezaldehyde SodiumBenzoate Benzoic acid
4

5. 2. Reformatsky Reaction
Defn-The aliphatic or aromatic aldehydes and ketones when react with
-bromoester and zinc metal in presence of dry ether give -
hydroxy esters. This reaction is called is Reformatsky Reaction.
Ex-1) When acetaldehyde treated with -bromoester and zinc metal in
presence of dry ether, -hydroxy ester is obtained.
C
H3 C
O
H + CH2 C
O
O
Br C2H5
Zn
Dry ether C
H C
O
O
O
C2H5
C
H3 CH2
Zn Br
H OH
CH C
O
O
O
C2H5
C
H3 CH2
H
Acetaldehyde  Bromo ethyl acetate
Hydroxy ethyl butanoate
Hydroxy ester


+ Zn
OH
Br
5

6. + CH2 C
O
O
Br C2H5
Zn
Dry ether
H OH
Benzaldehyde  Bromo ethyl acetate
Hydroxy phenyl ethyl butanoate
Hydroxy ester)
+ Zn
OH
Br
C
O
H C
H C
O
O
O
C2H5
CH2
Zn Br
C
H C
O
O
O
C2H5
CH2
H
Ex-2) When benzaldehyde treated with -bromoester and zinc metal in
presence of dry ether, -hydroxy ester is obtained.
6

7. Ex-1) When acetone is treated with -bromoester and zinc metal in
presence of dry ether, -hydroxy ester is obtained.
C
H3 C
O
CH3 + CH2 C
O
O
Br C2H5
Zn
Dry ether C C
O
O
O
C2H5
C
H3 CH2
Zn Br
C
H3
H OH
CH C
O
O
O
C2H5
C
H3 CH2
H
Acetone  Bromo ethyl acetate
Hydroxy ester)
Hydroxy ethyl butanoate
+ Zn
OH
Br
H
+
7

8. + CH2 C
O
O
Br C2H5
Zn
Dry ether
H OH
Acetonphenone  Bromo ethyl acetate
Hydroxy phenyl ethyl butanoate
Hydroxy ester)
+ Zn
OH
Br
C
O
CH3
C C
O
O
O
C2H5
CH2
Zn Br
C
H3
C C
O
O
O
C2H5
CH2
H
CH3
H
+
Ex-2) When acetophenone is treated with -bromoester and zinc metal
in presence of dry ether, -hydroxy ester is obtained.
The formed -hydroxy esters on further acid hydrolysis
followed by heating it gives ,  unsaturated acids.
8

9. 3. Perkin Reaction
Defn-The aromatic aldehydes when heated with anhydride of aliphatic
acid (containing at least two -hydrogens) and sodium salt of
same acid (catalyst) to form ,  unsaturated acids. This
reaction is called is Perkin Reaction.
 This reaction is given by Perkin in 1868 and hence this reaction is
called is called as Perkin Reaction.
Ex.-When benzaldehyde is heated with acetic anhydride and sodium
acetate at 180oC for 5 hours, Cinnamic acid is obtained.
C
O
H
C
H3
O
C
H3
O
O
C
H3 COONa
180oC
C
H CH COOH
C
H3 COOH
+
Benzaldehyde Acetic Anhydride
Cinnamic acid
9

10. Q- Explain the mechanism of Perkin Reaction.
Mechanism- It involves four steps as-
Step-I- Sodium acetate dissociates to give acetate ion, which abstracts
-hydrogen from acetic anhydride to form carbanion (A)
C
H3 C
O
ONa C
H3 C
O
O
-
+ Na
+
C
H3 C
O
O
-
C
H3 C
O
C
O
CH3
O
+ C
H2
-
C
O
C
O
CH3
O C
H3 C
O
OH
+
Carbaion (A)
10

11. Step-II- Carbanion (A) attacks on carbonyl carbon of benzaldehyde
to give intermediate anion (B)
+
C H
O
C
H2
-
C
O
C
O
CH3
O
Carbaion (A)
CH
O
-
CH2 C
O
C
O
CH3
O
(B)
..
Benzaldehyde
Step-III- Anion (B) protonated by acetic acid to form intermediate
(C). Which on loss water molecule to form , -unsaturated
mixed anhydride (D).
(B)
CH
O
-
CH2 C
O
C
O
CH3
O
H
+
CH
OH
C
H C
O
C
O
CH3
O
H
CH CH C
O
C
O
CH3
O
(D)
- H2O
(C)
11

12. Step-IV- , -unsaturated mixed anhydride (D) undergoes hydrolysis
to give cinnamic acid.
+
 unsaturated mixed anhydride
CH CH C
O
C CH3
O
O
CH CH C
O
OH
- H2O
CH3COOH
Cinnamic acid
12

13. 4. Mannich Reaction
Defn- Aliphatic or aromatic ketones containing -hydrogen when react
with formaldehyde and ammonia or primary amine or secondary
amine to form -amino ketones, this reaction is called as
Mannich Reaction.
Ex.- When acetone or acetophenone is reacted with formaldehyde and
dimethyl amine in methanol or HCl gives - amino ketone.
+
Acetophenone
C CH3
O
C
O
H H + N
H
CH3
CH3
CH3OH/ HCl
- H2O
C CH2
O
CH2 N
CH3
CH3
Formaldehyde
Dimethyl amine 3 - Diemethylamino -1 - phenyl -1 - propanone
i)
ii)
+
Acetone
C
H3 C CH3
O
C
O
H H + N
H
CH3
CH3
CH3OH /HCl
- H2O
C
H3 C CH2
O
CH2 N
CH3
CH3
Formaldehyde
Dimethyl amine
4 - Diemethylamino - 2 - butanone
13

14. Other examples of Mannich reaction using primary amine and
ammonia are as follows.
+
Acetone
C
H3 C CH3
O
C
O
H H + N
H2 CH3
CH3OH/ HCl
- H2O
C
H3 C CH2
O
CH2 NH CH3
Formaldehyde methyl amine
4 - Methylamino - 2 - butanone
+
Acetophenone
C CH3
O
C
O
H H + N
H2 CH3
CH3OH/ HCl
- H2O
C CH2
O
CH2 NH CH3
Formaldehyde
Methyl amine 3 - methylamino -1 - phenyl -1 - propanone
+
Acetone
C
H3 C CH3
O
C
O
H H +
CH3OH/ HCl
- H2O
C
H3 C CH2
O
CH2 NH2
Formaldehyde Ammonia
4 - amino - 2 - butanone
+
Acetophenone
C CH3
O
C
O
H H +
CH3OH/ HCl
- H2O
C CH2
O
CH2 NH2
FormaldehydeAmmonia
3 - amino -1 - phenyl -1 - propanone
NH3
NH3
1.
2
3
4
14

15. 5. Benzoin Condensation
Defn- Aromatic aldehydes do not containing -hydrogen on treatment
with aqueous alcoholic potassium cyanide or sodium cyanide
undergoes condensation to form -hydroxy ketones is called as
benzoin. This reaction is called as Benzoin condensation.
Ex.- When benzaldehyde is reacted with aqueous ethanolic solution of
potassium cyanide or sodium cyanide, condensation of two
molecules of benzaldehyde takes place to form benzoin.
+
C H
O
C
O
H
KCN/ NaCN
H2O + C2H5OH
Benzaldehyde
CH C
OH O
Benzoin
15

16. 6. Aldol Condensation
Defn-Aromatic or aliphatic aldehydes and ketones -hydrogen on treatment
with dil. alkali the it undergoes condensation to form -hydroxy
aldehyde called as Aldol or -hydroxy ketone called as Ketols
respectively, This reaction is called as Aldol condensation.
Ex.-When acetaldehyde is heated with dilute sodium hydroxide or
sodium carbonate, the it undergoes condensation of two molecules
of acetaldehydes to form -hydroxy butyraldehyde (aldol).
+
C
H3 C H
O
C
O
C
H3 H C
H3 CH CH2
OH
C
O
H
Acetaldehyde  - hydroxy butyraldehyde
dil. NaOH / Na 2CO3
Aldol
16

17.  Similarly, when acetone or acetophenone is heated in presence of
dil. NaOH, then it give -hydroxy ketone.
+
C
H3 C CH3
O
C
O
C
H3 CH3
C
H3 C CH2
OH
C
O
CH3
CH3
Acetone 4 - hydroxy 4 - methyl - 2 - pentanone
dil. NaOH / Na 2CO3
Ketol
+
C CH3
O
C CH2
OH
C
O
CH3
Acetophenone 3 - hydroxy 1, 3 - diphenyl - 1 - butanone
dil. NaOH / Na 2CO3
C CH3
O
Aldol on warming with dil. acid then it give  -unsaturated carbonyl
compound (Crotonalhyde)
C
H3 CH CH2
O
H
C
O
H
 - hydroxy butyraldehyde
Aldol
heat
C
H3 CH CH C
O
H
Crotonaldehyde
17

18. Reduction of Carbonyl Compounds
1. Clemmensen reduction
Defn- Aldehydes and ketones when refluxed with a large excess of
amalgamated zinc and hydrochloride acid, carbonyl group get reduced
to methylene group to give corresponding hydrocarbons. This reaction is
called as Clemmensen reduction.
Here >C=O convert into > CH2
R C R
1
O
2 Zn - Hg + 4 HCl
R CH2 R
1
+ 2 ZnCl 2 2 Hg H2O
+ +
Reflux
Examples- i)
ii)
C
H3 C H
O 2 Zn - Hg + 4 HCl
C
H3 CH3 + 2 ZnCl 2 2 Hg H2O
+ +
Reflux
Acetaldehyde
Ethane
C H
O
2 Zn - Hg + 4 HCl
+ 2 ZnCl 2
2 Hg H2O
+ +
Reflux
Benzaldehyde Toluene
CH3
18

19. Examples- iii)
C
H3 C CH3
O
2 Zn - Hg + 4 HCl
C
H3 CH2 CH3 + 2 ZnCl2 2 Hg H2O
+ +
Reflux
Acetone Propane
C CH3
O
2 Zn - Hg + 4 HCl
CH2 CH3+2ZnCl2 2 Hg H2O
+ +
Reflux
Acetophenone Ethyl Benzene
iv)
v)
O
2 Zn - Hg + 4 HCl
+ 2ZnCl2 2 Hg H2O
+ +
Reflux
Cyclohexanone Cyclohexane
19

20. 2. Wolf-Krishner reduction
Defn- Aldehydes and ketones on heating with hydrazine and a strong base like
KOH or sodium ethoxide at 450-470oC, carbonyl group get reduced to
methylene group to give corresponding hydrocarbons. This reaction is
called as Wolf-Kishner reduction.
Here >C=O convert into > CH2
R C R
1
O KOH / C2H5ONa
R C R
1
N NH2
+ H2O
+ +
N
H2 NH2 450
-
470
o
C
R CH2
R
1
N2
C
H3 C H
O KOH / C2H5ONa
+ +
N
H2 NH2 450
-
470
o
C
C
H3 CH3 N2
Acetaldehyde Hydrazine Ethane
Examples-
C H
O KOH / C2H5ONa
+ +
N
H2 NH2 450
-
470
o
C
CH3
N2
Acetophenone
Hydrazine
Ethyl Benzene
ii)
i)
20

21. 3. Meerwein-Ponndorf-Verley (MPV) reduction
Defn- Aldehydes and ketones when treated with aluminium isopropoxide in
isopropanol, carbonyl group get reduced to alcoholic group to give
corresponding alcohols. This reaction is called as Meerwein-
Ponndorf-Verley (MPV) reduction.
Here >C=O convert into > CH-OH
R
C
R1
O
3 +
C
H3
CH
C
H3
O
-
Al
3+
3
(CH3)2CH - OH
R
CH
R1
O
-
3
Al
3+
C
H3
C
C
H3
O
3
+
dil.H 2SO4
+
R
CH
R1
OH
3 Al(OH) 3
21

22. Examples-
C
H3 C H
O
[(CH 3)2CHO] 3Al
Acetaldehyde Ethanol
(CH3)2 -CH - OH
C
H3 CH2 OH
C H
O
CH2 OH
[(CH 3)2CHO] 3Al
(CH3)2 -CH - OH
Benzaldehyde Benzyl Alcohol
C
H3
C CH3
O
[(CH 3)2CHO] 3Al
Acetone 2 - Propanol
(CH3)2 -CH - OH
C
H3 CH CH3
O
H
C CH3
O
CH
OH
CH3
[(CH 3)2CHO] 3Al
(CH3)2 -CH - OH
Acetophenone 1 - Phenyl Ethanol
i)
ii)
iii)
iv)
22

23. 4. Reduction by using Lithium Aluminum Hydride
(LiAlH4)
 Aldehydes and ketones when treated with lithium aluminium hydride in
ether, carbonyl group get reduced to alcoholic group to give corresponding
alcohols.
Here >C=O convert into > CH-OH
R
C
R1
O
LiAlH4
Ether
R
CH
R1
OH
C
H3 C H
O
LiAlH 4
Acetaldehyde Ethanol
Ether
C
H3 CH2 OH
i)
Examples-
23

24. C H
O
CH2 OH
LiAlH 4
Ether
Benzaldehyde Benzyl Alcohol
C
H3 C CH3
O
LiAlH 4
Acetone 2 - Propanol
Ether C
H3 CH CH3
O
H
C CH3
O
CH
OH
CH3
LiAlH 4
Ether
Acetophenone 1 - Phenyl Ethanol
ii)
iii)
iv)
24