Transcript Chemistry 2100

Chemistry 2100
Lecture 5
R CHO
O
O
R C H
R C R'
R CO R'
Nomenclature
IUPAC names for aldehydes
– To name an aldehyde, change the suffix -e of the
parent alkane to -al.
– Because the carbonyl group of an aldehyde can
only be at the end of a parent chain and numbering
must start with it as carbon-1, there is no need to
use a number to locate the aldehyde group.
– For unsaturated aldehydes, indicate the presence
of a carbon-carbon double bond by changing the
ending of the parent alkane from -ane to -enal.
Numbering the carbon chain begins with the
aldehyde carbonyl carbon. Show the location of the
carbon-carbon double bond by the number of its
first carbon.
Nomenclature
• The IUPAC system retains common names
for some aldehydes, including these three.
O
CHO
CHO
H
OCH3
t rans-3-Phenyl-2-prop enal
(Cinn amald ehyd e; in
oil of cin namon)
Ben zaldehyde
(in almond s)
OH
Van illin
(from van illa
bean s)
Nomenclature
IUPAC names for ketones.
– The parent alkane is the longest chain that
contains the carbonyl group.
– Indicate the presence of the carbonyl group by
changing the -ane of the parent alkane -one.
– Number the parent chain from the direction that
gives the carbonyl carbon the smaller number.
– The IUPAC retains the common name acetone for
2-propanone.
O
O
1
Acetone
O
2
3
4
5
1
6
5-Meth yl-3-h exanone
2
2-Methylcycloh exanone
Nomenclature
To name an aldehyde or ketone that also
contains an -OH (hydroxyl) or -NH2 (amino)
group:
– Number the parent chain to give the carbonyl
carbon the lower number.
– Indicate an -OH substituent by hydroxy-, and an NH2 substituent by amino-.
– Hydroxyl and amino substituents are numbered
and alphabetized along with other substituents.
O
OH O
5
4
3
1
H
3-Hydroxy-4-meth ylp entanal
6
4
3
2
1
NH2
3-Amino-4-ethyl-2-h exanone
Nomenclature
Common names
The common name for an aldehyde is derived from
the common name of the corresponding carboxylic
acid.
– Drop the word "acid" and change the suffix -ic or -oic to aldehyde.
• Name each alkyl or aryl group bonded to the carbonyl
carbon as a separate word, followed by the word
"ketone”. Alkyl or aryl groups are generally listed
O in
order
of increasing
molecular Oweight.
O
O
CH3 CH
CH3 COH
Acetaldehyde Acetic acid
Methyl ethyl ketone Ethyl isopropyl ketone
Physical Properties
Physical Properties
N ame
diethyl ethe r
pe ntane
butanal
2-butanone
1-butanol
pr opanoic acid
bp
M ole cular
Str uctur al Formula Weight (amu) (°C)
CH3 CH2 OCH 2 CH3
34
74
CH3 CH2 CH2 CH2 CH 3 72
36
CH3 CH2 CH2 CHO
72
76
72
80
CH3 CH2 COCH3
74
117
CH3 CH2 CH2 CH2 OH
CH3 CH2 COOH
74
141
Preparations
O
R
C H
H
O
R
H
C
H
O
O
[ O]
R
C H
alde hyde
(1°)
O
H
R'
[ O]
R
C
ketone
(2°)
R'
[ O]

[ O]
R
C
carboxylic
O H
acid
O
R
C
carboxylic
O H
acid
O
R
C H
H
O
R
H
C
H
O
O
[ O]
R
C H
alde hyde
(1°)
O
H
R'
[ O]
R
C
ketone
(2°)
R'
[ O]

[ O]
R
C
carboxylic
O H
acid
O
R
C
carboxylic
O H
acid
O
R
C H
H
O
R
H
C
H
O
O
[ O]
R
C H
alde hyde
(1°)
O
H
R'
[ O]
R
C
ketone
(2°)
R'
[ O]

[ O]
R
C
carboxylic
O H
acid
O
R
C
carboxylic
O H
acid
O
R
C H
H
O
R
H
C
H
O
O
[ O]
R
C H
alde hyde
(1°)
O
H
R'
[ O]
R
C
ketone
(2°)
R'
[ O]

[ O]
R
C
carboxylic
O H
acid
O
R
C
carboxylic
O H
acid
O
R
C H
H
O
R
H
C
H
O
O
[ O]
R
C H
alde hyde
(1°)
O
H
R'
[ O]
R
C
ketone
(2°)
R'
[ O]

[ O]
R
C
carboxylic
O H
acid
O
R
C
carboxylic
O H
acid
Reactions
O
O
C
+
H Z
C
Z
Z = C, H
H
O
C
O
+
H Z
C
Z
Z = C, H
H
O
C
O
+
H Z
C
Z
Z = C, H
H
O
C
O
+

H Z

C
Z
Z = C, H
H
O
C
O
+

H Z

C
Z
Z = C, H
H
O
C
O
+

H Z

C
Z
Z = C, H
H
O
C
O
+

H Z

C
Z
Z = C, H
H
O
C
O
+

H Z

C
Z
Z = C, H
H
O
C
O
+

H Z

C
Z
Z = X, O, N
H
O
C
O
+

H Z

C
Z
OH
Z = X, O, N
H
CH3
C O
+ l
dryHHC
H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3
C O
+ l
dryHHC
H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC
H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3


C O
+ l
dryHHC


H OCH2 CH3
+
H
(xs )
CH 3
O
H
H
+
O
CH 2 CH 3
(f ull) acetal
H
O
CH2 CH3
he miac etal
CH 2 CH 3
C
+
O
C
or
TsOH / C6H 6
H
HOCH 2CH 3
CH3
H2 O
CH3
C
CH3
O
CH 3OH
H
CH3
O
H
C
+
CH3
O
hemik eta l
CH3
CH3OH
H+
CH3
O
CH3
C
CH3
+
O
ketal
CH3
H2 O
CH3
C
CH3
O
CH 3OH
H
CH3
O
H
C
+
CH3
O
hemik eta l
CH3
CH3OH
H+
CH3
O
CH3
C
CH3
+
O
ketal
CH3
H2 O
CH3
C
CH3
O
CH 3OH
H
CH3
O
H
C
+
CH3
O
hemik eta l
CH3
CH3OH (xs)
H+
CH3
O
CH3
C
CH3
+
O
ketal
CH3
H2 O
CH3
C
CH3
O
CH 3OH
H
CH3
O
H
C
+
CH3
O
hemik eta l
CH3
CH3OH (xs)
H+
CH3
O
CH3
C
CH3
+
O
ketal
CH3
H2 O
CH3
C
CH3
O
CH 3OH
H
CH3
O
H
C
+
CH3
O
hemik eta l
CH3
CH3OH (xs)
H+
CH3
O
CH3
C
CH3
+
O
ketal
CH3
H2 O
Cyclization
C
C
C
C
C
O
H
H
O
C
C
OH
C
O
H
C
C
C
C
C
O
H
H


O
C
C
OH
C
O
H
C
C
C
C
C
O

H
H



O
C
C
OH
C
O
H
C
C
C
C
C
O

H
H



O
C
C
OH
C
O
H
C
C
C
C
C
O

H
H



O
C
C
OH
C
O
H
C
C
C
C
C
O

H
H



O
C
C
OH
C
O
H
C
C
C
C
C
C

H
O
H



O
CC
C
C
C
O
CC
OH
OH
O H H
C
C
C
C
C
C

H
O
H



O
CC
C
C
C
O
CC
OH
OH
O H H
C
C
C
C
C
C

H
O
H



O
CC
C
C
C
O
CC
OH
OH
O H H
H
1
C
O
6
H
2
OH
HO
3
H
H
4
OH
H
5
O H
6
CH 2 OH
glucose
CH2 OH
5
4
HO
OH
6
H
H
O
CH 2 OH
5
1
4
OH
O
3
2
OH
HO
3
O H
O
1
2
OH
H
H
1
C
O
6
H
2
OH
HO
3
H
H
4
OH
H
5
O H
6
CH 2 OH
glucose
CH2 OH
5
4
HO
OH
6
H
H
O
CH 2 OH
5
1
4
OH
O
3
2
OH
HO
3
O H
O
1
2
OH
H
H
1
C
O
6
H
2
OH
HO
3
H
H
4
OH
H
5
O H
6
CH 2 OH
glucose
CH2 OH
5
4
HO
OH
6
H
H
O
CH 2 OH
5
1
4
OH
O
3
2
OH
HO
3
O H
O
1
2
OH
H
H
1
C
O
6
H
2
OH
HO
3
H
H
4
OH
H
5
O H
6
CH 2 OH
glucose
CH2 OH
5
4
HO
OH
6
H
H
O
CH 2 OH
5
1
4
OH
O
3
2
OH
HO
3
O H
O
1
2
OH
H
H
1
C
O
6
H
2
OH
HO
3
H
H
4
OH
H
5
O H
6
CH 2 OH
glucose
CH2 OH
5
4
HO
OH
6
H
H
O
CH 2 OH
5
1
4
OH
O
3
2
OH
HO
3
O H
O
1
2
OH
H
H
1
C
O
6
H
2
OH
HO
3
H
H
4
OH
H
5
O H
6
CH 2 OH
glucose
CH 2 OH
5
4
HO
OH
3
O H
O
1
2
OH
H
H
1
C
2
OH
HO
3
H
H
4
H
5
OH
O H
CH 2 OH
glucose
6
CH62CH
OH2 OHH
4
H
H
5
O
O1
OH 5
HO
6
HO
H
6
H
O
5
4
4
3
HO
3
H
H
CH 2 OH
OH
O
2
2
OH
OH
-glucose
1
H
OH
HO
3
O H
O
1
2
OH
H
Reduction
• The carbonyl group of an aldehyde or ketone
is reduced to an -CHOH group by hydrogen in
the presence of a transition-metal catalyst.
– Reduction of an aldehyde gives a primary alcohol.
– Reduction a ketone gives a secondary alcohol.
O
H + H2
transition
metal catalyst
Pentanal
O + H2
Cyclopen tan on e
tran sition
metal catalyst
OH
1-Pentanol
OH
Cyclopen tanol
Reduction
H :-
+
C O
H C O
H3 O +
-
H C O-H
Hydride
ion
O
O-
NaBH4
O
C
H
+
H3 O
O-H
H
H
1 . NaBH4
CH2 OH
2 . H2 O
Cin namaldehyde
Cinnamyl alcoh ol
• Reduction by NaBH4 does not affect a carboncarbon double bond or an aromatic ring.
Tollens
O
R
C
H
+
Ag(NH 3)2
O
R
C
H
+
Cu
+2
(citrate)
O
OHH2O
R
O
+
0
Ag
O
Benedict
OHH2O
C
R
C
O
+
Cu 2O
Keto-Enol Tautomerism
O H
C C C C C C
'
'




O H
C C C C C C
'
'




O H
C C C C C C
'
'




O H
C C C C C C
'
'




O H
C C C C C C
'
'




O H
C C C C C C
'
'




O H
C C C C C C
'
'




O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
tautomers
O
H
O
H
C
C
C
C
keto
e nol
"enolizable"
O
CH3
CH2
C H
?
O
CH3
CH
H2
C H
?
O
CH3
CH
H2
C H
H
CH3
CH
O
C H
CH 3
H
H
O
C
C
CH 3
O H
O
CH
H3
CH 3
CH
CH 3
C CH 3
CH 3
CH
H
CH 3
C
CH 2
CH 3
H
H
O
C
C
CH 3
O H
O
CH
H3
CH 3
CH
H
CH 3
C CH
H3
CH 3
CH
H
CH 3
C
CH 2
CH 3
H
H
O
C
C
CH 3
O H
O
CH
H3
CH 3
CH
H
CH 3
C CH
H3
CH 3
CH
H
CH 3
C
CH 2
CH 3
H
H
O
C
C
CH 3
O H
O
CH
H3
CH 3
CH
H
CH 3
C CH
H3
CH 3
CH
H
CH 3
C
CH 2
CH 3
CH 3
CH3
O
OH
H
H
OH
OH
OH
O
CH 3
CH 3
CH3
O
OH
H
H
OH
OH
OH
enediol
O
CH 3
CH 3
CH3
O
OH
H
H
H
OH
OH
OH
H
enediol
O
CH 3
CH 3
CH3
O
OH
H
H
H
OH
OH
OH
H
enediol
O
CH 3
CH 3
CH3
O
OH
H
H
H
OH
OH
OH
H
enediol
O
O
O
H
HO
OH
O
CH
OH
CH2 OH
O
H
OH
O
CH
HO
OH
CH 2 OH
O
O
O
CH
OH
CH2 OH
O
O
H
HO
OH
O
CH
OH
CH2 OH
O
H
OH
O
CH
HO
OH
CH 2 OH
O
O
O
CH
OH
CH2 OH
O
O
H
HO
OH
O
CH
OH
CH2 OH
O
H
OH
O
CH
HO
OH
CH 2 OH
O
O
O
CH
OH
CH2 OH
CH2
CH
OH
e nolize
C O
CH2
OP O3
dihydroxyace tone
phosphate
-2
ketoniz e
O
OH
ke tonize
C OH
CH2 OP O3
e ne diol
-2
enolize
C
H
H C OH
CH 2 OPO3
glyc eraldehyde
3-phosphate
-2
CH2
CH
OH
e nolize
C O
CH2
OP O3
dihydroxyace tone
phosphate
-2
ketoniz e
O
OH
ke tonize
C OH
CH2 OP O3
e ne diol
-2
enolize
C
H
H C OH
CH 2 OPO3
glyc eraldehyde
3-phosphate
-2
CH2
CH
OH
e nolize
C O
CH2
OP O3
dihydroxyace tone
phosphate
-2
ketoniz e
O
OH
ke tonize
C OH
CH2 OP O3
e ne diol
-2
enolize
C
H
H C OH
CH 2 OPO3
glyc eraldehyde
3-phosphate
-2
CH2
CH
OH
e nolize
C O
CH2
OP O3
dihydroxyace tone
phosphate
-2
ketoniz e
O
OH
ke tonize
C OH
CH2 OP O3
e ne diol
-2
enolize
C
H
H C OH
CH 2 OPO3
glyc eraldehyde
3-phosphate
-2
CH2
CH
OH
e nolize
C O
CH2
OP O3
dihydroxyace tone
phosphate
-2
ketoniz e
O
OH
ke tonize
C OH
CH2 OP O3
e ne diol
-2
enolize
C
H
H C OH
CH 2 OPO3
glyc eraldehyde
3-phosphate
-2
CH2
CH
OH
e nolize
C O
CH2
OP O3
dihydroxyace tone
phosphate
-2
ketoniz e
O
OH
ke tonize
C OH
CH2 OP O3
e ne diol
-2
enolize
C
H
H C OH
CH 2 OPO3
glyc eraldehyde
3-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
CH2
CH OH
OH
H
enolize
H
OH
ketonize
H
OH
CH 2 O
H
OH
O
HO
O
PO 3
f ructose-6-phosphate
-2
HO
H
H
OH
H
OH
CH2 O
enediol
PO 3
-2
C
H
OH
ketonize
HO
H
enolize
H
OH
H
OH
CH 2 O
PO 3
glucose-6-phosphate
-2
Carboxylic Acids
Carboxylic Acids
• In this chapter, we study carboxylic acids,
another class of organic compounds
containing the carbonyl group.
• The functional group of a carboxylic acid is a
carboxyl group, which can be represented in
any one of three ways.
O
C-OH
COOH
CO2 H
Nomenclature
IUPAC names
– For an acyclic carboxylic acid, take the longest
carbon chain that contains the carboxyl group as
the parent alkane.
– Drop the final -e from the name of the parent
alkane and replace it by -oic acid.
– Number the chain beginning with the carbon of the
carboxyl group.
– Because the carboxyl carbon is understood to be
carbon 1, there is no need to give it a number.
Nomenclature
– In these examples, the common name is given in
parentheses. O
O
6
1
3
OH
Hexanoic acid
(Caproic acid)
1
OH
3-Methylbutanoic acid
(Isovaleric acid)
– An -OH substituent is indicated by the prefix
hydroxy-; an -NH2 substituent by the prefix amino.
OH
O
5
1
OH
5-Hydroxyhexan oic acid
H2 N
COOH
4-A min ob enzoic acid
Nomenclature
– To name a dicarboxylic acid, add the suffix -dioic
acid to the name of the parent alkane that contains
both carboxyl groups; thus, -ane becomes -anedioic
acid.
– The numbers of the carboxyl carbons are not
O at the ends of
indicated becauseOthey can beOonly
1
3
1
HO
2
the chain.
OH
HO
OH
O
Ethan edioic acid Prop aned ioic acid
(Malonic acid )
(Oxalic acid )
O
HO
4
O
5
1
OH
O
Butaned ioic acid
(Succinic acid)
HO
O
O
1
OH
Pen tanedioic acid
(Glutaric acid)
HO
6
1
OH
O
Hexan edioic acid
(Ad ipic acid)
Nomenclature
Structure
HCOOH
CH3 COOH
CH3 CH2 COOH
CH3 (CH2 ) 2 COOH
CH3 (CH2 ) 3 COOH
CH3 (CH2 ) 4 COOH
CH3 (CH2 ) 6 COOH
CH3 (CH2 ) 8 COOH
CH3 (CH2 ) 1 0 COOH
CH3 (CH2 ) 1 2 COOH
CH3 (CH2 ) 1 4 COOH
CH3 (CH2 ) 1 6 COOH
CH3 (CH2 ) 1 8 COOH
IU PAC N ame
(acid)
methanoic
ethan oic
propanoic
bu tanoic
pen tanoic
hexan oic
octanoic
decanoic
dodecanoic
tetradecan oic
hexad ecanoic
octadecanoic
eicosan oic
Common
N ame
formic
acetic
propionic
bu tyric
valeric
cap roic
cap rylic
cap ric
lauric
myristic
palmitic
stearic
arachid ic
D erivation
Latin : formica, ant
Latin : acet um, vinegar
Greek: propion, firs t fat
Latin : buty rum, b utter
Latin : valere, to be s trong
Latin : caper, goat
Latin : caper, goat
Latin : caper, goat
Latin : laurus , laurel
Greek: my ris tikos, fragrant
Latin : palma, palm tree
Greek: st ear, solid fat
Greek: arachis, p eanut
Nomenclature
For common names, use, the Greek letters alpha
(), beta (), gamma (), and so forth to locate
substituents.
O
C-C-C-C-OH
  
4
3 2 1
O
O
H2 N
4

2
1
OH
OH

OH
4-A min ob utanoic acid
2-Hyd roxypropan oic acid
(-A min obu tyric acid; GABA) (-Hydroxyprop ion ic acid;
lactic acid)
Physical Properties
hydrogen bonding
between two
molecules
H3 C
O
+
H O
C
C
O
H
+
O
-
CH3
Physical Properties
Carboxylic acids are more soluble in water than are
alcohols, ethers, aldehydes, and ketones of comparable
molecular weight.
Structu re
N ame
CH3 COOH
CH3 CH2 CH2 OH
CH3 CH2 CHO
acetic acid
1-prop anol
prop anal
Boilin g
Solubility
Molecular Poin t
Weigh t
(°C) (g/100 mL H 2O)
60.5
118
infinite
97
60.1
infinite
58.1
48
16
CH3 (CH2 ) 2 COOH butan oic acid
CH3 (CH2 ) 3 CH2 OH 1-pentan ol
pentan al
CH3 (CH2 ) 3 CHO
88.1
88.1
86.1
163
137
103
infinite
2.3
slight
HA
+
H2O
Ka
larger Ka
=
A–
+
H3O+
[A–] [H3O+]
[HA]
increased [H3O+]
stronger acid
HA
+
H2O
Ka
larger Ka
=
A–
+
H3O+
[A–] [H3O+]
[HA]
increased [H3O+]
stronger acid
HA
+
H2O
Ka
larger Ka
=
A–
+
H3O+
[A–] [H3O+]
[HA]
increased [H3O+]
stronger acid
HA
+
H2O
Ka
larger Ka
=
A–
+
H3O+
[A–] [H3O+]
[HA]
increased [H3O+]
stronger acid
RCOOH
+
Ka
H2O
=
RCOO–
[RCOO–] [H3O+]
[RCOOH]
+
H3O+
RCOOH
+
Ka
H2O
=
RCOO–
[RCOO–] [H3O+]
[RCOOH]
+
H3O+
Comparative acidities of 0.1 M aqueous solutions of representative acids HA
HCl
HOAc
PhOH
EtSH
EtOH
HOH
[H3O+], M
Ka
% ionized
~1  107
~100
1.8  10–5
3.3  10–10
1.3
0.0036
1.3  10–3
3.6  10–6
2.88
5.44
2.5  10–11
0.0016
1.6  10–6
5.80
1.3  10–16
0.0001
1.0  10–7
7.00
1.8  10–16
0.0001
1.0  10–7
7.00
~0.1
acids > phenols ~ thiols > water ~ alcohols
pH
1.00
Fatty Acids
Table 18.3 The Most Abundant Fatty Acids in Animal
Fats, Vegetable Oils, and Biological Membranes.
C arbon A tom s:
Doubl e B onds *
Structure
Saturated Fatty A cids
12:0
CH3 ( CH2 ) 1 0 COOH
C ommon
N ame
Melting Point
(°C )
lauric a cid
44
14:0
CH3 ( CH2 ) 1 2 COOH
myri sti c acid
58
16:0
CH3 ( CH2 ) 1 4 COOH
palmi tic acid
63
18:0
CH3 ( CH2 ) 1 6 COOH
s tearic aci d
70
20:0
CH3 ( CH2 ) 1 8 COOH
arachid ic acid
77
U nsaturated Fatty A cid s
16:1
CH3 ( CH2 ) 5 CH= CH( CH2 ) 7 COOH
palmi toleic acid
1
18:1
CH3 ( CH2 ) 7 CH= CH( CH2 ) 7 COOH
oleic acid
16
18:2
CH3 ( CH2 ) 4 ( CH= CHCH2 ) 2 ( CH 2 ) 6 COOH linol eic acid
18:3
CH3 CH2 ( CH= CHCH2 ) 3 ( CH 2 ) 6 COOH
20:4
CH3 ( CH2 ) 4 ( CH= CHCH2 ) 4 ( CH 2 ) 2 COOH arachid onic acid
linol eni c acid
* The fi rs t number is the num ber of carbons in the f atty acid; the s econd is the
number of carbon-carb on doubl e bonds in its hydrocarbon chai n.
-5
-11
-49
Fatty Acids
Unsaturated fatty acids generally have lower
melting points than their saturated
counterparts.
COOH Stearic acid (18:0)
(mp 70°C)
COOH Ole ic acid (18;1)
(mp 16°C)
COOH Linoleic acid (18:2)
(mp-5°C)
COOH Linolenic acid (18:3)
(mp -11°C)
Fatty Acids
Saturated fatty acids are solids at room
temperature.
– The regular nature of their hydrocarbon chains
allows them to pack together in such a way as to
maximize interactions (by London dispersion
forces) between their chains.
COOH
COOH
COOH
COOH
COOH
Fatty Acids
In contrast, all unsaturated fatty acids are
liquids at room temperature because the cis
double bonds interrupt the regular packing of
their hydrocarbon chains.
COOH
COOH
COOH
COOH
COOH
Soaps
Soaps
Decarboxylation
• Decarboxylation: The loss of CO2 from a carboxyl
group.
• Almost all carboxylic acids, when heated to a very
high temperature, will undergo thermal
decarboxylation.
O
RCOH
decarboxylation
high temperature
RH + CO2
• Most carboxylic acids, however, are resistant to
moderate heat and melt and even boil without
undergoing decarboxylation.
• An exception is any carboxylic acid that has a
carbonyl group on the carbon  to the COOH group.
Decarboxylation
• Decarboxylation of a -ketoacid.
O
O
O
warm
 
OH
3-Oxobutano ic acid
(Acetoacetic acid)
+
CO 2
Aceto ne
• The mechanism of thermal decarboxylation involves
(1) redistribution of electrons in a cyclic transition
state followed by (2) keto-enol tautomerism.
enol of
a ketone
O
H
O
(1)
O
(A cyclic six-membered
trans itio n s tate)
O
H
O
C
O
(2)
O
+
CO 2
Decarboxylation
• An important example of decarboxylation of a ketoacid in biochemistry occurs during the oxidation
of foodstuffs in the tricarboxylic acid (TCA) cycle.
Oxalosuccinic acid, one of the intermediates in this
cycle, has a carbonyl group (in this case a ketone)  to
one of its three carboxyl groups.
only this carboxyl
has a C=O beta to it .
HOOC
O
 
COOH
COOH
Oxalosuccinic acid
O
HOOC
COOH + CO2
-Ketoglutaric acid