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
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
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
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
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
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
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
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
