Nuecleophilic addition to c=o

“ Nuecleophilic Addition to c=o ”
G. P. Sadawarte
Assistant Professor
Dept. of Chemistry,
B.P. Arts, S.M.A. Science, K.K.C. Commerce
College Chalisgaon

Nature of c=o
• A carbon–oxygen bond is a polar covalent bond
• Oxygen has 4 nonbonding electrons in 2 lone pairs
:O:
• or to share two pairs of electrons to form the
carbonyl functional
• One sigma & one pi bond
O O-
+

Nature of c=o
O
H+
O+
H O H
O H
A
O H
O
B
Acid catalysed Base catalysed

Reactivity
electronic withdrawing group(-I) increase Rate of nucleophilic substitution reaction
O
CH3
O
CH3
O
CH3
OHC
O
CH3
Cl O2N
Br
Structure and reactivity
Inductive effect
electronic donating group(+I) decreass Rate of nucleophilic substitution
reaction
O
CH3
O
CH3
O
CH3
H
H
H

Reactivity
CHO
NO2
CHO CHO
OCH3
O
electronic donating group(+R) decreass Rate of nucleophilic substitution reaction
electronic withdrawing group(-R) increass Rate of nucleophilic substitution reaction
Resonance Effect
K=1420 K=210 K=32 Very small

Simple Addition reaction
Hydration
O
R
R
H
O
H
A
H O
R
R
H
O
H
A
H
R
R O+
H2
OH
R
R
OH
OH
Slow
- H+
Acid catalysed
TS

H
O
H
H
B
O
R
R O-
R
R
H
O
H
H
B
R
R OH
O-
R
R
OH
OH
H2O
Base Catalysed
TS

Addition of alcohol
O
R
R
ROH
+ H+
R
R
OH
OR
ROH
+ H+
R
R
OR
OR
-H2O
O
R
R
+
HO
HO
H+
R
R O
O
CH2
CH2

O
R
R
H+
OH
R
R
+ ROH
R
R
OH
O+
R
H
-H+
R
R
OH
OR
H+
-OH
R
R OR
+
ROH R
R OR
R O+
H R
R
OR
OR
Fast
Mechanism

O
R
R
H+
OH
R
R
+ RSH
R
R
OH
S
R
H
-H+
R
R
OH
SR
H+
-OH
R
R SR
+
RSH R
R SR
R S+
H R
R
SR
SR
Fast

Addition of derivatives of ammonia
O
H
R
+ NH2- OH
H
R
N
OH
O
H
R
+
H
R
N
NH
NH2-NH-Ph
Ph
O
H3C
C6H5
+ NH2- OH
H3C
C6H5
N
OH
Hydroxyl amine
Hydroxyl amine
Phenyl Hydrazin

O
H
R
+ NH2- OH
Hydroxyl amine H
R O-
N+
H
H OH
H
R O+
H2
N
H
OH
-H2O
- H+
H
R
N OH
H
R O-
N+
H
H OH
H
R OH
N
H
OH
+H+
- H+
+H+
H
R O+
H2
N
H
OH
Mechanism

Cannizzaros reaction
Cannizzaros Reaction
• It involves the base-induced disproportionation of
two molecules of a non-enolizable aldehyde to give
a primary alcohol and a carboxylic acid
• Mild Base KOH 50 %
• Doesn’t conation Alpha H
• Stanislao Cannizzaros

O
H
Ph
+ O
H
Ph
O
KO
Ph
+ CH2
HO
Ph
Benzaldehyde
KOH
Potassium Benzoate Benzyl Alcohol
Cannizzaros Reaction

Mechanism
O
H
Ph
OH -
Ph
HO
O -
H
+
O
H
Ph
Ph
HO
O -
H
+
O
H
Ph
O
HO
Ph
+
O -
H
Ph
H
O
KO
Ph
+
OH
H
Ph
H
O
HO
Ph
+
O -
H
Ph
H
K+

Crossed Cannizzaros reaction
Crossed Cannizzaros Reaction
O
H
H
+ O
H
Ph
O
KO
H
+ CH2
HO
Ph
KOH
Intramolecular Cannizzaros Reaction
O O
H H
KOH
CH2
O OH
KO

Aldol Condensation
• Having alpha H
• “Aldol" (aldehyde + alcohol)
• It is a condensation reaction in which an enol
or an enolate ion reacts with a carbonyl
compound to form a β-hydroxyaldehyde or β-
hydroxy ketone
• An aldol reaction followed by dehydration to
give a conjugated enone.

Aldol Condensation
Aldol reaction was discovered
by Aleksandr P. Borodin
C
O
H
H3C
+ C
O
H
H3C
Acetaldehyde
NaOH C
HO
H3C
H
H2
C C
O
H
beta Hydraoxy aldehyde

Aldol Condensation
Mechanism
O
H
H3C
OH -
O
H
H2C
-
C
O
H
H3C
C
O
H
H2C
-
+ C
-
O
H3C
H
H2
C C
O
H

Aldol Condensation
C
-
O
H3C
H
H2
C C
O
H
H+
C
HO
H3C
H
H2
C C
O
H
C
HO
H3C
H
C C
O
H
H+
H
H
C
H3C
H
C C
O
H
H

Aldol Condensation
C
O
CH3
H3C
+ C
O
H
H3C
Acetone
NaOH
Aldol Condensation
C
HO
H3C
CH3
H2
C C
O
CH3
beta Hydraoxy Ketone

Aldol Condensation
Mechanism
O
CH3
H3C
OH -
O
CH3
H2C
-
C
O
CH3
H3C
C
O
CH3
H2C
-
+ C
-
O
H3C
CH3
H2
C C
O
CH3

Aldol Condensation
C
-
O
H3C
CH3
H2
C C
O
CH3
H+
C
HO
H3C
CH3
H2
C C
O
CH3
C
HO
H3C
CH3
C C
O
CH3
H+
H
H
C
H3C
CH3
C C
O
CH3
H

Perkin Reaction
• The Perkin reaction is an reaction developed
by English chemist William Henry Perkin
• It is used to prepare cinnamic acids.
• When aromatic aldehyde and an acid
anhydride reacts in the presence of an alkali
salt of the acid, It gives an α,β-unsaturated
aromatic acid
H
O

Perkin Reaction
Mechanism
Benzaldehyde Cinnamic Acid
H
O
+
H3C CO
O
CO
H3C
CH3COOH
H
C
C
H
COOH
acetic anhydride
CH3COOH CH3COO -
sodium acetate
+ Na+
Acetic acid
H3C CO
O
CO
H3C
CH3COO -
H2
-
C CO
O
CO
H3C
+

Perkin Reaction
H
O
H2
-
C CO
O
CO
H3C
+
O-
H
H2
C CO
O
CO
H3C
OH
H
O
C
O
CO
H3C
H+
H
H
-H2O
Hydrolysis
OH
H
H
C
C
H
COOH

Wittig Reaction
• Organophosphorus ylides react with aldehydes
or ketones to give substituted alkenes in a
transformation called the Wittig reaction.
• This reaction is named for George Wittig who
was awarded the Nobel prize for this work in
1979

Wittig Reaction
Acetaldehyde
Propene
H3C H
O
+ H3C
PPh3
CH2
Ph3P O
+
Triphenyl
phosphine
oxide
Mechanism
H3C H
O
+
PPh3
CH2
H3C H
O
CH2
PPh3
PPh3
O
CH3
Propene
Triphenyl
phosphine
oxide
+

Wittig Reaction
O
+
PPh3
CH2
PPh3
O
Triphenyl
phosphine
oxide
Methylene
cyclo hexene
+
O
+
PPh3
CH2
O
CH2
PPh3
PPh3
O
Triphenyl
phosphine
oxide
Methylene
cyclo hexene
+

Reformatsky Reaction
• The Reformatsky reaction (Reformatskii) is an
reaction which condenses aldehydes or ketones
with α-halo esters using metallic zinc to form
β-hydroxy ester
• This reaction was discovered by Sergey
Nikolaevich Reformatsky
• Rassian Chemist

• Organozinc compounds are prepared from α-halo
esters in the same manner as Grignard Reagents.
• This reaction is possible due to the stability of
esters against organozinc.
• Due to the very low basicity of zinc enolates, there
is hardly any competition from proton transfer,
and the scope of carbonyl addition partners is
quite broad.

• In presence of ketones or aldehydes, the
organozinc compounds react as the
nucleophilic partner in an addition to give β-
hydroxy esters.
Br
OC2H5
O
+
H
O
OH
OC2H5
O
Zn

Mechanisum
Br
OC2H5
O
Zn
BrZn
OC2H5
O
OC2H5
O Zn Br
OC2H5
O Zn Br
H
O
+
O Zn Br
+
H2
C
H
O
OC2H5
O Zn Br
+
H2
C
H
O
OC2H5
H+
/ H2O
C
H2
OH
OC2H5
O
Beta Hydroxy Ester
alpha Bromo Ester
H OH

Reaction with LiAlH4
C
O
H
H3C
+ Li Al H4
C
HO
H
H3C
H
ROH
4

Reaction with LiAlH4
C
O
H
H3C
+
Acetaldehyde
Li Al H4
C
H3 Al -
O
H
H3C
H
Li +
C
H3 Al -
O
H
H3C
H
Li +
Mechanism
+ C
O
H
H3C
3
C
Al -
O
H
H3C
H
Li +
4
C
Al -
O
H
H3C
H
Li +
4
ROH 4
C
HO
H
H3C
H
+

Nuecleophilic addition to c=o

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