Chemistry Reference
In-Depth Information
R
R
R
H
+
CO
+
H
C
+
CO
OH
G
G
G
H
2
O
(weak nucleophile)
H
H
+
R
C
+
H
C
G
R
OH
G
proton
transfer
H
O
HO
C
O + GH
C
R
R
OH
HG
+
(better leaving group
when protonated)
Figure 8.18
The mechanism of acid-catalysed hydrolysis.
Base-catalysed hydrolysis
This reaction is easier to follow; the nucleophile in this case is the strongly
basic OH
ion, which attacks the d
carbon of the carbonyl group directly
(Figure 8.19).
-
OH (strong nucleophile)
OH
R
HO
O + G
-
CO
C
C
R
O
-
G
R
G
Planar
Tetrahedral
Substitution
product
Leaving
group
Figure 8.19
The mechanism of base-catalysed hydrolysis.
Note that in base-catalysed hydrolysis the acid formed by hydrolysis
instantaneously reacts with the excess of base to form the salt of the acid.
The free acid may be obtained, if desired, by acidification of the mixture.
