19: Carboxylic Acids

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learning objectives

After reading this chapter and completing ALL the exercises, a student can be able to

describe the structure and physical properties of carboxylic acids and carboxylate salts (section 21.1)
explain and predict the relative acidity of carboxylic acids using resonance, hybridization, and substituent effects (section 21.2)
determine the structure of carboxylic acids from their elemental analysis and spectral data (MS, IR ¹H NMR & ¹³C NMR) (section 21.3)
predict the products and specify the reagents to synthesize carboxylic acids (section 21.4)
recognize and classify the major reactions of carboxylic acids (section 21.5)
show the general mechanism for Nucleophilic Acyl Substitution Reactions (section 21.5)
predict the products and specify the reagents for reactions of carboxylic acids with
- sulfonyl chlorides (section 21.5)
- alcohols (section 21.6)
- diazomethane (section 21.7)
- amines (section 21.8)
- reducing agents (section 21.9)
combine the reactions studied to date to develop efficient and effective multiple-step synthesis

Please note: IUPAC nomenclature and important common names of carboxylic acids were explained in Chapter 3.

It can useful is often required to memorize the structures for the following common names: formic acid, acetic acid, acetyl chloride, acetic anhydride, acetic formic anhydride, ethyl acetate, sodium and potassium salts of formate, acetate, and benzoate, acetamide, benzamide, acetonitrile, benzonitrile, carbonic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and phthalic acid

19.1: Structure and Properties of Carboxylic Acids and their Salts
The acidic proton of the carboxylic acid and the size of the carbon chain influence the physical properties of carboxylic acids.
19.2: Acidity of Carboxylic Acids
The structural effects on relative acidity are reviewed from chapter 1 with a closer look at the effects of electron-donating and electron-withdrawing groups on benzoic acid.
19.3: Spectroscopy of Carboxylic Acids
The spectroscopy of carboxylic acids is strongly influenced by the acidic proton and the formation of dimers.
19.4: Synthesis of Carboxylic Acids
Methods from previous chapters to synthesize carboxylic acids are reviewed and new reactions to synthesize carboxylic acids from nitriles and organometallic compounds are introduced. The Carboxylic Acid Derivatives and Nitriles can be hydrolyzed to carboxylic acids These hydrolysis reactions are more relevant to biochemistry and metabolism than multiple-step synthesis.
19.5: Reactions of Carboxylic Acids Overview
Carboxylic acids undergo four different types of reactions: acid-base, nucleophilic acyl substitution, reduction, and alpha substitution. Acyl chlorides, anhydrides, esters, and amides (the carboxylic acid derivatives) can be synthesized from nucleophilic acyl substitution reactions with carboxylic acids.
19.6: Condensation of Acids with Alcohols: The Fischer Esterification
The Fischer esterification reaction also produces water as a side product so it is described as a condensation reaction.
19.7: Methyl Ester Synthesis Using Diazomethane
The reaction of carboxylic acids with diazomethane looks straight forward. However, the high reactivity of diazomethane requires special handling.
19.8: Condensation of Acids with Amines
Direct conversion of carboxylic acids to amides can be synthetically difficult because of the stability of the carboxylate intermediate. Dicyclohexylcarbodiimide (DCC) can be used to facilitate the formation of amides.
19.9: Reduction of Carboxylic Acids
Lithium aluminum hydride can be used to reduce carboxylic acids to primary alcohols.
19.10: Biochemically Interesting Carboxylic Acids
Carboxylic acid functional groups are part of many important and interesting biochemical molecules, such as fatty acids, metabolites, nutrients, and chemical messengers.
19.11: Additional Exercises
This section has additional exercises for the key learning objectives of the chapter.
19.12: Solutions to Additional Exercises
This section has the solutions to the additional exercises from the previous section.