1) The Claisen-Schmidt condensation involves the condensation of aromatic aldehydes without alpha hydrogens and aliphatic aldehydes, ketones, or esters with active alpha hydrogens in the presence of alkaline solutions to form alpha, beta unsaturated aldehydes, ketones, or esters. 2) The Dakin reaction involves the replacement of aldehyde or ketone groups on O-hydroxy or P-hydroxy aromatic aldehydes by hydroxyl groups when reacted with alkaline hydrogen peroxide. 3) The Oppenauer oxidation reaction consists of oxidizing secondary alcohols to ketones in the presence of aluminum isopropoxide and excess ketone which

1. Reactions and Reagents
POC-III Unit-V
1
B.Suresh MS.(Pharm.), (Ph.D).
Asst.Proff. Palamuru University, MBNR

2. Claisen-schmidth condensation
Condensation of aromatic aldehydes having no α- Hydrogen
with aliphatic aldehydes, ketones or esters having active α H
in presence of 10% alkali solution to give α, β unsaturated
aldehydes, ketones or esters known as claisen-schmidth
codensation
2

3. Cont..
H
O
H3C CH3
O
H
O
H3C O
O
10% NaOH
10% NaOHC2H5
+
+ ?
?
3

4. Cont..
H
O
H3C CH3
O
H
O
H3C O
O
10% NaOH
10% NaOH
CH3
O
O
O
C2H5
C2H5
+
+
ethyl cinnamate
(E)-4-phenylbut-3-en-2-one
ethyl acetate
propan-2-one
benzaldehyde
benzaldehyde
4

5. Mechanism of reaction
5
C H
O
OH
H
H
H
H2C H
O
H2C H
O
H
O
O
H
O
OH
H
O
H
H
O
-H2O
+
Step 1
STep 2
H2O

6. Dakkin reaction
 This reaction involves the replacement of aldehydes or ketone
group of the O-hydroxy, P-Hydroxy aromatic aldehydes by
hydroxyl group on reaction with alkaline hydrogen peroxide
6

7. 7
Mechanism of reaction

8. Oppenauer’s oxidation reaction
 This reaction consists of oxidation of 2o alcohols to
ketones in presence of aluminium iso-propoxide and in
excess of ketone which acts as dehydrogenating agent
8

9. Mechanism of reaction
9

10. Applications
Preparation of Codienone from Codiene
Preparation Progesterone from Pregnenolone
10

11. Wolff kishner reduction reaction
 Reduction of hydrazone, semicarbazone and azide of aldehyde or
ketones to hydrocarbons in vigorously basic conditions (NaOH
and their salts of alkoxides) by release of N2 gas is known as
wolf kishner reduction reaction
11

12. Mechanism of reaction
Formation of hydrazone
R1 R2
N
N
H
H
OH
R1 R2
N
N
H
H2O R1 R2
N
N
H
OH
H
R1 R2
N
N
H
H2O
-N2R1 R2
HH
Wolff kishner reduction reaction
12

13.  Preparation of camphene from camphor
13

14. Clemmensen Reduction
 Aldehydes or ketones up on treating with Zinc amalgam
and hydrochloric acid results in the formation of their
corresponding hydrocarbons is known as clemmensen
reduction
 Clemmensen reduction is particularly effective at
reducing aryl-alkyl ketones, such as those formed in a
Friedel-Crafts acylation.
14

15. 15
Mechanism of reaction
R1 R2
O
Zn(Hg)
R1 R2
O
Zn
R1 R2
O Zn
R1 R2
Zn
H
Cl
R1 R2
ZnClH H
Cl
R1 R2
HH

16. Applications
 This reaction has widely used to convert a carbonyl group into a
methylene group.
 Also important application in the preparation of polycyclic aromatics
and aromatics containing unbranched side hydrocarbon chains.
 To reduce aliphatic and mixed aliphatic-aromatic carbonyl compounds
16

17. Birch reduction
An organic reaction where the aromatic ring undergo 1,4
reduction to produce uncongugated cyclohexadiene this
reaction conducted by Na/Li metal in liquid ammonia and in
presence of alcohols
17
H
H
HH
HH
Na/Li & Liq NH3
C2H5OH
Na/Li & Liq NH3
C2H5OH
1,4-dihydronaphthalene
cyclohexa-1,4-diene

18. 18
Mechanism of reaction

19. Applications
19

20. Sodium borohydride
 It is also known as sodium tetraborate is an inorganic compound with the formula of
NaBH4
 Sodium borohydride was first prepared by reaction of sodium hydride (NaH) with
trimethylborate B(OMe)3.
 NaBH4 is less reactive than LiAlH4
 It is only powerful enough to reduce aldehydes, ketones and acid
 chlorides to alcohols, without attacking other redusible groups such as esters, amides,
acids and nitriles.
 An aldehyde is reduced to 1o & ketone to a 2o alcohol respectively.
 Selective (chemoselectivity) reagent
20

21. 21
Mechanism of reaction
Cont..

22. Applications/Examples
22

23. Cont..
23

24. Lithium alluminium Hydarate
 LiAlH4 is Very powerful reducing reagent, reacts violently with water
and alcohol
 Reduces carbonyl, carboxylic acid, esters and reduces nitrile, amide &
aryl nitro group to amine
 Reduces C-X bond, acetylene to olefin and opens epoxide
 LiAlH4 is a stronger reducing agent than NaBH4 due to weaker Al-H
bond
 LiAlH4 is used to reduce compounds that are nonreactive toward
NaBH4
24

25. Preparation
 It is produced by the gradual addition of the LiH to
limited quantity of anhydrous AlCl3 in ether
25

26. Reduction of carbonyls
26
Mechanism of reaction

27. 27
H
O LiAlH4
O LiAlH4
OH
H
H
OH
H
Reduction of with carbonyls
Reduction of carboxylic acids and derivatives

28. Reduction of carboxylic acids and derivatives
28
Reduction of with carbonyls

29. Reduction of Oxime, Nitriles, and nitro compounds
29

30. Reduction of Epoxides, Ozonoids
30
LiAlH4
?
LiAlH4
?H3C O
CH3
C2H5
O3
LiAlH4H3C O
CH3
C2H5
H3C
OH
H3C OH+
CH3
C2H5
O O
O
+ CH3OH + C2H5OH