Transcript Carboxylic Acids: Properties and Synthesis

Chapter 18
Carboxylic Acids:
Properties and Synthesis
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Assignments
• In-text problems:
– 18-1 and 18-2
– 18-4 (IUPAC only!!)
– 18-6 to 18-10
18-14 to 18-20
• End-of-chapter problems:
–1
– 3 to 9
– 11 to 16
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Sect. 18.1: IUPAC Nomenclature
• -oic acid
IUPAC ending
• -carboxylic acid
IUPAC ending for ring compounds
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O
CH 3 CH
CH 2 C
OH
CH 3
3-Methylbutanoic acid
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O
CH 3 CH 2 CH 2 CH
C
OH
Cl
2-Chloropentanoic acid
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O
OH
OCH3
4-methoxy-3,5-hexadienoic acid
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H
C
OH
O
Cyclohexanecarboxylic acid
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O
1
OH
2
3
CH3
3-methylcyclohexanecarboxylic acid
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O
OH
Benzoic acid
or Benzenecarboxylic acid
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O
1
OH
2
4
3
Numbering system
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O
OH
Cl
2-chlorobenzoic acid
or 2-chlorobenzenecarboxylic acid
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O
OH
para
ortho
meta
Common names for benzoic acids
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Common names!
O
OH
Cl
ortho-chlorobenzoic acid
o-chlorobenzoic acid
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IUPAC only
O
OH
NO2
Cl
3-chloro-2-nitrobenzoic acid
or 3-chloro-2-nitrobenzenecarboxylic acid
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IUPAC only
O
3
(1)
2
1
OH
(2)
(3)
NO2
3-(3-nitrophenyl)propanoic acid
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Common Names
O
H
C
O
O
OH
CH 3 C
Formic acid
OH
Acetic Acid
CH 3 CH 2 C
Propionic Acid
O
CH 3 CH 2 CH 2 C
Butyric Acid
OH
O
OH
CH 3 CH 2 CH 2 CH 2 C
OH
Valeric Acid
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Some more common names
• butyric acid and isobutyric acid
• valeric acid and isovaleric acid
• Fatty acids: myristic, palmitic and stearic
acids
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O
CH 3 CH
C
OH
CH 3
2-Methylpropanoic acid
Isobutyric acid
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Fatty acids
O
OH
Stearic acid
O
OH
Palmitic acid
O
OH
Myristic acid
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Sect. 18.2: carboxylate salts
• endings: oate
• combine with sodium, potassium etc.
• Example: sodium butanoate (IUPAC) or
sodium butyrate (common)
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Carboxylate Ion Formation
O
O
R
CH2 C
OH + NaOH
R
CH2 C
O
Na
+
+
H2O
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Sect. 18.3: hydrogen bonding
O
R
C
H
O
C
R
O
O
H
Carboxylic acids are very high boiling!
Low MW acids are water soluble and
High MW acids are water insoluble!
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Sections 18.4, 18.5, 18.6
• Much of this material is review!
• Key table: Table 18-18 on page 62!!
• Skip Section 18.7.
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Resonance Effects
Effect
Acid
Base
Electron
strengthen weaken
withdrawing by
resonance (-R)
Electron
weaken
releasing by
Resonance (+R)
Examples
-NO2
and
O
O
strengthen
R
and
R
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Electron-withdrawing effects
involving resonance (-R)
These substituents strengthen
acids and weaken bases on the
benzene ring
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Substituents with ElectronWithdrawing Resonance Effects
O
NO2
nitro
C
OH
carboxyl
O
C
OR
N
alkoxycarbonyl
C
acyl
SO3H
cyano
O
C
R
sulfo
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O
O
O
OH
H+
O2N
O2N
• Electron-withdrawing
Effects:
– strengthen acids
– weaken bases
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A substituted benzoic acid
COOH
3.41
O2N
Benzoic acid = 4.19
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Electron releasing effect by
resonance (+R)
These substituents weaken acids
and strengthen bases on the
benzene ring
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Substituents with ElectronReleasing Resonance Effects
..
OH
..
hydroxy
..
OR
..
alkoxy
O
..
SH
..
mercapto
CH3
methyl
..
O
..
CR3
C
R
acyloxy
alkyl
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O
O
O
OH
O
R
H+
O
R
Electron-releasing Effects:
- weaken acids
- strengthen bases
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Substituted benzoic acid
COOH
4.46
CH3 O
Benzoic acid = 4.19
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COOH
H3C
pKa = 4.36
Benzoic Acid: pKa = 4.19
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Inductive Effect
Effect
Acid
Base
Examples
Electron
strengthen weaken
withdrawing by
inductive effect
(-I)
electron
releasing by
inductive effect
(+I)
-NO2
and
X
O
weaken
and
strengthen
O
R
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Electron withdrawing by
inductive effects (-I)
These substituents strengthen
acids and weaken bases
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Substituents with ElectronWithdrawing Inductive Effects on
substituted acetic acids
NO2
nitro
OH
hydroxy
carbonyl
OR
alkoxy
cyano
NR2
dialkylamino
O
C
C
N
X
halo
+
N(CH3)3 trimethylammonium
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O
CH3 C
O
OH
pKa = 4.75
O2N CH2 C
O
F
CH2 C
O
OH
2.66
HO
O
Cl
CH2 C
OH 1.68
CH2 C
OH
3.83
OH
2.34
O
OH
2.86
H2N
CH2 C
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COOH
COOH
2.16
3.47
NO2
NO2
Inductive
and resonance
Inductive, only
COOH
3.41
O2 N
Resonance and weak inductive
Benzoic Acid: pKa = 4.19
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Another substituted benzoic acid
• 4-chlorobenzoic acid is weird!! Resonance
effect will decrease acidity, but inductive
effect wins out.
COOH
3.98
Cl
Benzoic acid = 4.19
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Electron releasing effect by
inductive effect (+I)
These substituents weaken acids
and strengthen bases
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Substituents with ElectronReleasing Inductive Effects
O
CH3
methyl
CR3
alkyl
C
O
O
carboxylate
oxide
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O
O
CH3 C
OH
4.75
CH3 CH C
OH
4.86
CH3
O
CH3 CH2 C
CH3 O
OH
4.88
CH3 C
C
OH
5.05
CH3
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COOH
H3C
pKa = 4.36
Benzoic Acid: pKa = 4.19
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Sect. 18.8: Carbonation of
Grignard Reagents
O
R
+
MgX
CO2
ether
R
C
O
R
C
O
+
MgX
O
O
+
MgX
+ HX
R
C
OH
+ MgX2
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Sect. 18.9: Formation of Nitriles
R
CH2 Cl
_
+ :C
N:
R
CH2 C
N
+
Cl
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Hydrolysis of Nitriles
O
R
CH2 C
N
+
H2O
R
CH2 C
OH
+ NH3
hydrolysis occurs under both acid and base conditions
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Sect. 18.10: Oxidation of
Primary Alcohols
O
R
4 KMnO4
+
CH 2 OH
R
heat
+
C
+
O K
4 MnO2 +
4 H2O
+ KOH
O
R
C
O
+
O K
+
+
H
R
C
OH
+
+
K
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Oxidation of Side Chains
O
R
C
OH
KMnO4
heat
+
n CO2 +
n H2O
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O
OH
lots of
+ CO2 + H2O
KMnO4
heat!!!
O
OH
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