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Chapter 21 The Chemistry of Carboxylic Acid Derivatives. Carboxylic Acid Derivatives. Carboxylic acid derivative : a compound that has an acyl group bonded to an electronegative atom or substituent that can act as a leaving group in a substitution reaction - PowerPoint PPT Presentation
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Chapter 21The Chemistry of Carboxylic Acid Derivatives
Carboxylic Acid Derivatives• Carboxylic acid derivative: a compound that has an acyl group
bonded to an electronegative atom or substituent that can act as a leaving group in a substitution reaction– can be hydrolyzed under acidic of basic conditions to give a
carboxylic acid
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Structures of Carboxylic Acid Derivatives
321.1 Nomenclature and Classification of Carboxylic Acid Derivatives
Reactions of Carboxylic Acid Derivatives• Chemistry dominated by nucleophilic acyl substitution rxns:
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Hydrolysis Reactions1) Hydrolysis of Esters
a) Basic Hydrolysis (Saponification)b) Acid Catalyzed Hydrolysis
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Basic Hydrolysis
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Acid Catalyzed Hydrolysis
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2) Hydrolysis of Amides
• Happens under both acidic and basic conditions• Conditions harsher than those of ester hydrolysis
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+ NH4+/NH2
-
• Basic Hydrolysis
• Acidic Hydrolysis
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3) Hydrolysis of Nitriles• Occurs in both acidic and basic environments• More extreme conditions are required compared to those of esters
and amides
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• Basic hydrolysis
1121.7 Hydrolysis of Carboxylic Acid Derivatives
• Acidic hydrolysis
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• Imidic acids can be viewed as the nitrogen-analogs of enols
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Problem• Write out the mechanism for the following rxn:
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Nucleophilic Acyl Substitution Reactions
• The conditions for hydrolysis for these derivatives can differ considerably
1521.7 Hydrolysis of Carboxylic Acid Derivatives
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Reactions of Acid Chlorides with Amines: Aminolysis
1821.8 Reactions of Carboxylic Acid Derivatives with Nucleophiles
Conversion of Acid Chlorides into Esters: Alcoholysis
1921.8 Reactions of Carboxylic Acid Derivatives with Nucleophiles
Reactions of Acid Chlorides with Carboxylate Salts: Preparation of Anydrides
2021.8 Reactions of Carboxylic Acid Derivatives with Nucleophiles
Problems
1) Give the products for the following rxns:
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2) Draw the mechanism for the following reaction:
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Reactions of Anhydrides with Nucleophiles
2321.8 Reactions of Carboxylic Acid Derivatives with Nucleophiles
Reactions of Esters with Nucleophiles
• Transesterification:
2421.8 Reactions of Carboxylic Acid Derivatives with Nucleophiles
Problems
• Give the products for the following rxns:
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Reduction Carboxylic Acid Derivatives
1) Reduction of Esters• LiAlH4 preferred over NaBH4
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-78°C, DIBAH = Diisobutyl aluminum hydride
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2) Reduction of Amides to Amines– Net effect is conversion of C=O to CH2
2821.9 Reduction of Carboxylic Acid Derivatives
Reduction of Amides to Amines
• Note how the amide reduction differs from that of ester reduction
2921.9 Reduction of Carboxylic Acid Derivatives
• Note that a protonolysis step with aqueous acid follows the LiAlH4 reduction
• This is followed by base to free the amine
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3121.9 Reduction of Carboxylic Acid Derivatives
3221.9 Reduction of Carboxylic Acid Derivatives
3) Reduction of Nitriles to Primary Amines
3321.9 Reduction of Carboxylic Acid Derivatives
• Two successive nucleophilic additions occur
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• Intermediate imine not isolated
3521.9 Reduction of Carboxylic Acid Derivatives
4) Reduction of Acid Chlorides to Aldehydes– The Rosenmund reduction:
– H2 gas over Pd on C• Poisoned with BaSO4 or quinoline
– Keeps aldehyde from further reducing to alcohol
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• Derivatives of LiAlH4 can also be used
• Can also use DIBAH
3721.9 Reduction of Carboxylic Acid Derivatives
Problems
• Draw the products for the following rxns:
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Reactions of Esters with Grignard Reagents
• Tertiary alcohol produced• Two substituents are identical
4021.10 Reactions of Carboxylic Acid Derivatives with Organometallic Reagents
Reactions of Acid Chlorides Grignard Reagents
4121.10 Reactions of Carboxylic Acid Derivatives with Organometallic Reagents
Reactions of Acid Chlorides with R2CuLi
• R2CuLi = Gilman reagent
• Dialkylcuprates are less reactive than Grignard reagents• Allow rxn to stop at ketone• Only works with acid chlorides, not with other carboxylic acid
derivatives
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Problems
• Draw the product for the following rxns:
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