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Carboxylic acids and TheirDerivatives
Carboxylic acids and TheirDerivatives
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Diacids
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Physical Properties of carboxylic acids
Hydrogen bondingSolubility in water(lower acids)
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Acidity of carboxylic acids
pKa = -log Ka
As Ka increase or pKa decrease, the acidity increase١٣
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Resonance and Inductive effect
Conversion of acids to salts
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Preparation of carboxylic acids
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From Alkenes• Oxidative cleavage of an alkene with KMnO4 gives a
carboxylic acid if the alkene has at least one vinylichydrogen (see Section 7.8)
Based on McMurry, OrganicChemistry, Chapter 20, 6th
edition, (c) 2003
17
20.6 Preparation of Carboxylic Acids
• Oxidation of a substituted alkylbenzene with KMnO4or Na2Cr2O7 gives a substituted benzoic acid (seeSection 16.10)
• 1° and 2° alkyl groups can be oxidized, but tertiarygroups are not
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Carboxylation of GrignardReagents
• Grignard reagents react with dry CO2 to yield a metalcarboxylate
• Limited to alkyl halides that can form Grignardreagents (see 17.6)
Based on McMurry, OrganicChemistry, Chapter 20, 6th
edition, (c) 2003
19
Mechanism of GrignardCarboxylation
• The organomagnesium halide adds to C=O of carbondioxide
• Protonation by addition of aqueous HCl in a separatestep gives the free carboxylic acid
Based on McMurry, OrganicChemistry, Chapter 20, 6th
edition, (c) 2003
20
Hydrolysis of Nitriles• Hot acid or base yields carboxylic acids• Conversion of an alkyl halide to a nitrile (with cyanide
ion) followed by hydrolysis produces a carboxylic acidwith one more carbon (RBr RCN RCO2H)
• Best with primary halides because eliminationreactions occur with secondary or tertiary alkylhalides
Based on McMurry, OrganicChemistry, Chapter 20, 6th
edition, (c) 2003
21
• Hot acid or base yields carboxylic acids• Conversion of an alkyl halide to a nitrile (with cyanide
ion) followed by hydrolysis produces a carboxylic acidwith one more carbon (RBr RCN RCO2H)
• Best with primary halides because eliminationreactions occur with secondary or tertiary alkylhalides
From Alcohols• Oxidation of a primary alcohol or an aldehyde with
CrO3 in aqueous acid
Based on McMurry, OrganicChemistry, Chapter 20, 6th
edition, (c) 2003
22
Reactions of carboxylic acids
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EstersNomenclature
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Examples
O
OMe H
OO
OPh
O
OEt
CH3 O
O
Cl
OEt
OH
CH3CH3 O
O
O
OMe H
OO
OPh
O
OEt
CH3 O
O
Cl
OEt
OH
CH3CH3 O
O
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Lactones (Cyclic Esters)
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Reactions of Esters with Grignard Reagent
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Formation of Amides (Ammonolysis of Esters)
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Reduction of EstersEsters can be reduced to primary alcohols
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The Cliasen Condensation
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Acid HalidesThey are prepared from the reaction of acids with thionyl chloride or
phosphorus halides
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Reactions of acid chloridesAcid chlorides react rapidly with most nucleophiles such as water,
alcohols and ammoniaAcyl halides have irritating odors. Benzoyl chlorid is a lachrymator(tear gas)
CH3 Cl
O
CH3 OH
O
CH3 OR
O
CH3 NH2
O
H2O
EtOH
NH3
+
+
+
HCl
HCl
HCl
CH3 Cl
O
CH3 OH
O
CH3 OR
O
CH3 NH2
O
H2O
EtOH
NH3
+
+
+
HCl
HCl
HCl
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Reaction with Grignard Reagent
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Preparation of mixed anhydrides
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• Mixed anhydridesCH3 O
OO
Ph
Acetic benzoic anhydride٤٣
Nucleophilic substitution of anhydrides
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Amides• Nomenclature
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• Properties of Amides
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Amide Resonance
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Reactions of Amides (Hydrolysis and Reduction)
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