REACTIONS OF ALDEHYDES,
KETONES AND CARBOXYLIC
ACIDS
Things to Consider
1. Because the bond strength of the C=O
bond (804 kJ/mol) is much stronger than
the C=C bond (620 kJ/mol) the carbonyl
group is less reactive than the C=C bond
found in alkenes.
2. Because the carbonyl group is very polar,
it does undergo many reactions but these
are different from those that the alkenes
undergo.
1.
Combustion
aldehyde or ketone + O2  CO2 + H2O
Hydrogenation (a reduction reaction)
2.
P
t/1
0
1
M
P
a
a
ld
e
h
y
d
e
/k
e
to
n
e+
H
2
•
a
lc
o
h
o
l
Aldehydes produce primary alcohols.
H H
HC C C
H H
O
HH H
O
P
t/1
0
1
M
P
a
+H
2
H C C CH
H H H
H
1
p
r
o
p
a
n
o
l
p
r
o
p
a
n
a
l
•
Ketones produce secondary alcohols
HOH
H
H
HO
P
t
/1
0
1
M
P
a
CC C
H
H+
H
2
H
H
p
r
o
p
a
n
o
n
e
HC C C H
HHH
2
p
r
o
p
a
n
o
l
3. Oxidation (reaction with KMnO4 or H2Cr2O7)
• ONLY ALDEHYDES
ald
eh
y
d
e+w
ater
O
C
H
K
M
n
O
4
H
C
r2O
2
7
carb
o
x
y
licacid
H
K
M
n
O
4
C H+H
OHC
2
O
2r
2
7
H
C
C H+
2
H
+
H
e
th
a
n
o
ica
c
id
(a
c
e
tica
c
id
)
K
M
n
O
4
H C C C H+H
OHC
2
O
2r
2
7
H
H
p
ro
p
a
n
o
n
e
H
H
O
e
th
a
n
a
l
HO H
O
N
O
R
E
A
C
T
IO
N
Qualitative Tests for Aldehydes and Ketones
1. Fehling’s Solution (copper (II) solution)
•
This is an oxidation reaction in which the blue
copper(II) solution will form an orange
precipitate if there is a reaction.
aldehydes + Cu2+  carboxylic acid + Cu (s)
blue solution  orange precipitate
ketones + Cu2+  NO REACTION
solution stays blue
2. Tollen’s Reagent (Silver Mirror Test)
•
•
Silver ions in ammonia (NH3)
Commercially used to “silver mirror” glass.
H
3
+ N
a
ld
e
h
y
d
e+A
g
c
o
lo
u
rle
s
ss
o
lu
tio
n
+
ketone+A
g
N
H
3
c
a
rb
o
x
y
lica
c
id+
A
g
(s
)
b
la
c
kp
re
c
ip
ita
te
N
OR
E
A
C
T
IO
N
solutionstayscolourless
Reactions of Carboxylic Acids
• Organic acids are “weak” acids, therefore they do
not completely ionize in water.
c
a
r
b
o
x
y
lic
a
c
id+
w
a
te
r
c
a
r
b
o
x
y
la
te
io
n
+
h
y
d
r
o
n
iu
m
io
n
O
H
O
2
C +
H
H
C O
3
e
th
a
n
o
ic
a
c
id
(
a
c
e
tic
a
c
id
)
O
+
C +
H
O
3
H
C O
3
e
t
h
a
n
o
a
te
io
n
(
a
c
e
ta
te
io
n
)
1. Neutralization
c
a
rb
o
x
y
lica
c
id+
b
a
s
e
O
+N
a
O
H
C
H
H
C O
3
e
th
a
n
o
ica
c
id
(
a
c
e
tica
c
id
)
m
e
ta
lc
a
rb
o
x
y
la
te+w
a
te
r
O
C
+
H
O
2
+
a
H
C ON
3
s
o
d
iu
m
e
th
a
n
o
a
te
(
s
o
d
iu
m
a
c
e
ta
te
)
2. Test for Carboxylic Acids
• Reaction with carbonate.
c
a
r
b
o
x
y
l
i
c
a
c
i
d
+
s
o
d
i
u
m
c
a
r
b
o
n
a
t
e
s
a
l
t(
"
o
a
t
e
"
)
+
c
a
r
b
o
n
d
i
o
x
i
d
e
+
w
a
t
e
r
O
O
N
a
C
O
2
3
(
a
q
)
C +
H
H
C O
3
C
+
C
O
+
H
O
2
(
g
)
2
+
N
a
H
CO
3
s
o
d
i
u
m
e
t
h
a
n
o
a
t
e
(
s
o
d
i
u
m
a
c
e
t
a
t
e
)
e
t
h
a
n
o
i
c
a
c
i
d
(
a
c
e
t
i
c
a
c
i
d
)
3. Formation of an Ester (reaction with an alcohol)

H
S
O
/
2
4
c
a
r
b
o
x
y
l
i
c
a
c
i
d
+
a
l
c
o
h
o
l
HO
H
m
e
t
h
a
n
o
l
HO H
O
H
O
CH+
HCC
2

H
S
O
/
2
4
C
H
HCC + H
O
H
O
H
H
e
t
h
a
n
o
i
c
a
c
i
d
(
a
c
e
t
i
c
a
c
i
d
)
e
s
t
e
r+
w
a
t
e
r
H
H
m
e
t
h
y
l
e
t
h
a
n
o
a
t
e
(
m
e
t
h
y
l
a
c
e
t
a
t
e
)