C Y
O
R
C Y
O
R
NH 2 NH 2
C Y
OH
R
NHNH 2
C Y
OH 2
R
NHNH 2
C Y
R
NNH 2
H
C Y
R
NNH 2
NH 2 NH 2
..
:
+
+
Hydrazone
± H +
+ H 2 O
..
..
..
Dry H +
..
..
:
+
..
..
:
..
:
:
..
:
:
..
..
Neutral tetrahedral
intermediate
H 3 O +
H 3 O +
..
+
Addition of secondary amine to carbonyl compounds: preparation of
enamines
Secondary amine reacts with aldehyde and ketone to produce enamine. An
enamine is an a,b-unsaturated tertiary amine. Enamine formation is a
reversible reaction, and the mechanism is exactly the same as the mechanism for imine formation, except the last step of the reaction.
NR' 2
C Y
RCH
RCH 2 C
O
Y
Y = H or R
H 3 O +
Enamine
Dry H +
+ H 2 O
+ R' 2 NH
: :
Mechanism.
C Y
O
RCH 2
C Y
O
RCH 2
NHR' 2
C Y
OH
RCH 2
NR' 2
C Y
OH 2
RCH 2
NR' 2
C Y
RCH
NR' 2
C Y
RCH
NR' 2
H
R' 2 NH
..
:
+
+
Enamine
± H +
+ H 2 O
Dry H +
..
..
:
+
..
..
:
:
:
:
:
..
Neutral tetrahedral intermediate
Addition of water to carbonyl compounds: acid-catalysed hydration.
Preparation of diols
Aldehyde and ketone reacts with water in the presence of aqueous acid or
base to form hydrate. A hydrate is a molecule with two hydroxyl groups on
the same carbon. It is also called gem-diol. Hydration proceeds through
the two classic nucleophilic addition mechanisms with water in acid
5.3 ADDITION REACTIONS
219