CARBOXYLIC ACIDS

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CARBOXYLIC ACIDS
Properties and Synthesis
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NOMENCLATURE
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IUPAC NOMENCLATURE

• -oic acid IUPAC ending
• -carboxylic acid IUPAC ending for ring compounds

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Naming
3-Methylbutanoic acid b-Methylbutyric
acid Isovaleric acid
2-Chloropentanoic acid a-Chlorovaleric acid
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Naming
2-Methylpropanoic acid a-Methylpropionic
acid Isobutyric acid
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More Naming
Benzoic acid Benzenecarboxylic acid
Cyclohexanecarboxylic acid
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Common Names
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Formula Common Name Source IUPAC Name Melting Point Boiling Point
HCO2H formic acid ants (L. formica) methanoic acid 8.4 ºC 101 ºC
CH3CO2H acetic acid vinegar (L. acetum) ethanoic acid 16.6 ºC 118 ºC
CH3CH2CO2H propionic acid milk (Gk. protus prion) propanoic acid -20.8 ºC 141 ºC
CH3(CH2)2CO2H butyric acid butter (L. butyrum) butanoic acid -5.5 ºC 164 ºC
CH3(CH2)3CO2H valeric acid valerian root pentanoic acid -34.5 ºC 186 ºC
CH3(CH2)4CO2H caproic acid goats (L. caper) hexanoic acid -4.0 ºC 205 ºC
CH3(CH2)5CO2H enanthic acid vines (Gk. oenanthe) heptanoic acid -7.5 ºC 223 ºC
CH3(CH2)6CO2H caprylic acid goats (L. caper) octanoic acid 16.3 ºC 239 ºC
CH3(CH2)7CO2H pelargonic acid pelargonium (an herb) nonanoic acid 12.0 ºC 253 ºC
CH3(CH2)8CO2H capric acid goats (L. caper) decanoic acid 31.0 ºC 219 ºC
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SYNTHESIS OF CARBOXYLIC ACIDS
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Oxidation of Primary Alcohols with
KMnO4
two a-hydrogens
MnO2
precipitate
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Oxidation of Primary Alcohols
with K2Cr2O7
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Oxidation of Side Chains
Example
D
KMnO4
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Carbonation of Grignard Reagents
( or Alkyllithium Compounds )
( R-Li )
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Formation of Nitriles and Hydrolysis
DMSO
H2SO4
H2O
SN2
heat
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SYNTHESIS OF CARBOXYLIC ACIDS
( DUE TO LACK OF SPACE REACTION CONDITIONS ARE
ABBREVIATED)
( benzene R sidechain R )
KMnO4
KMnO4
KMnO4
CrO3
or KMnO4
H2SO4
CrO3
H2O
H2SO4
H2SO4
DIBAL or
NaCN acetone
CO2
Rosenmund
KMnO4
H2O
H2SO4
SOCl2
Li or Mg
H2O
or
Chap 19
This is all stuff you know!
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Physical Properties of Carboxylic Acids
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Physical Properties of Some Organic Compounds
Formula IUPAC Name Molecular Weight Boiling Point Water Solubility
CH3(CH2)2CO2H butanoic acid 88 164 ºC very soluble
CH3(CH2)4OH 1-pentanol 88 138 ºC slightly soluble
CH3(CH2)3CHO pentanal 86 103 ºC slightly soluble
CH3CO2C2H5 ethyl ethanoate 88 77 ºC moderately soluble
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CH3CH2CO2CH3 methyl propanoate 88 80 ºC slightly soluble
CH3(CH2)2CONH2 butanamide 87 216 ºC soluble
CH3CON(CH3)2 N,N-dimethylethanamide 87 165 ºC very soluble
CH3(CH2)4NH2 1-aminobutane 87 103 ºC very soluble
CH3(CH2)3CN pentanenitrile 83 140 ºC slightly soluble
CH3(CH2)4CH3 hexane 86 69 ºC insoluble
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ACIDITY
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Carboxylate Ion Formation
They are acids, ya know !
carboxylate ion
carboxylic acid
pKa 5
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Protonation and Deprotonation of a Carboxylic
Acid
..

..
..
..


..
-
..
..
H2SO4
NaOH

..
..
..

H2SO4

..
..

..
equivalent structures
due to resonance

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• Electron-withdrawing Groups
• strengthen acids
• weaken bases
• Electron-releasing Groups
• weaken acids
• strengthen bases

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Substituents with Electron-Withdrawing Resonance
( - R ) Effects
X
Y
-R substituents strengthen acids and weaken
bases
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Substituents with Electron-Releasing Resonance (
R ) Effects
hydroxy
alkoxy
mercapto
acyloxy
methyl
alkyl
dialkylamino
amino
fluoro
chloro
bromo
iodo
R substituents weaken acids and strengthen
bases
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Substituents with Electron-Withdrawing
( - I ) Inductive Effects
X
carboxyl
cyano
alkoxycarbonyl
sulfonic acid
alkoxy
acyl
dialkylamino
hydroxyl
fluoro
mercapto
bromo
amino
iodo
chloro
trimethylammonium
nitro
-I substituents strengthen acids and weaken
bases
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Substituents with Electron-Releasing Inductive (
I ) Effects
R
methyl
alkyl
carboxylate
oxide
I substituents weaken acids and strengthen
bases
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increasing acidity
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ortho
ortho
meta
meta
para
para
Benzoic Acid pKa 4.19
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4.06
4.08
4.48
4.46
2.97
Benzoic Acid pKa 4.19
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Benzoic Acid pKa 4.19
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Acidity of Carboxylic Acids
Compound pKa Compound pKa
HCO2H 3.75 CH3CH2CH2CO2H 4.82
CH3CO2H 4.74 ClCH2CH2CH2CO2H 4.53
FCH2CO2H 2.65 CH3CHClCH2CO2H 4.05
ClCH2CO2H 2.85 CH3CH2CHClCO2H 2.89
BrCH2CO2H 2.90 C6H5CO2H 4.20
ICH2CO2H 3.10 p-O2NC6H4CO2H 3.45
Cl3CCO2H 0.77 p-CH3OC6H4CO2H 4.45
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Reactions of Carboxylic Acids

• Nucleophiles that are also strong bases react
  with carboxylic acids by removing a proton first,
  before any nucleophilic substitution reaction can
  take place.

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Nucleophilic acyl substitution reactions of
carboxylic acids
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• Treatment of a carboxylic acid with thionyl
  chloride (SOCl2) affords an acid chloride.
• This is possible because thionyl chloride
  converts the OH group of the acid into a better
  leaving group, and because it provides the
  nucleophile (Cl) to displace the leaving group.

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• Although carboxylic acids cannot readily be
  converted into anhydrides, dicarboxylic acids can
  be converted to cyclic anhydrides by heating to
  high temperatures.
• This is a dehydration reaction because a water
  molecule is lost from the diacid.

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ESTERIFIKASI ASAM KARBOKSILAT
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• Esterification of a carboxylic acid occurs in the
  presence of acid but not in the presence of base.
• Base removes a proton from the carboxylic acid,
  forming the carboxylate anion, which does not
  react with an electron-rich nucleophile.

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• Intramolecular esterification of ?- and
  ?-hydroxyl carboxylic acids forms five- and
  six-membered lactones.

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• Carboxylic acids cannot be converted into amides
  by reaction with NH3 or an amine because amines
  are bases, and undergo an acid-base reaction to
  form an ammonium salt before nucleophilic
  substitution occurs.
• However, heating the ammonium salt at high
  temperature (gt100C) dehydrates the resulting
  ammonium salt of the carboxylate anion to form an
  amide, although the yield can be low.

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• The overall conversion of RCOOH to RCONH2
  requires two steps
• 1 Acid-base reaction of RCOOH with NH3 to form
  an ammonium salt.
• 2 Dehydration at high temperature (gt100C).

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• A carboxylic acid and an amine readily react to
  form an amide in the presence of an additional
  reagent, dicyclohexylcarbodimide (DCC), which is
  converted to the by-product dicyclohexylurea in
  the course of the reaction.

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• DCC is a dehydrating agent.
• The dicyclohexylurea by-product is formed by
  adding the elements of H2O to DCC.
• DCC promotes amide formation by converting the
  carboxy group OH group into a better leaving
  group.

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Carboxylic Acid Derivatives
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Related Carbonyl Derivatives
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Related Carbonyl Derivatives