Chapter 20The Chemistry of Carboxylic Acids

Carboxylic Acids

• General structure:

• Characteristic functional group is called the carboxy group

220.1 Nomenclature of Carboxylic Acids

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Acetic acid Butyric acid Caproic acid

Palmitic acid

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Common Nomenclature

• Change the “-yl” (or “-oyl”) of the acyl group to “ic acid”

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Acetyl group

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More Complicated Common Nomenclature

• Dicarboxylic acids

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β-chlorovaleric acid

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IUPAC Nomenclature

• Replace the “-e” of the alkane name with “-oic acid”• The carbonyl carbon is numbered as C1

• For multiple carboxyl groups, retain the “-e” in the alkane name and insert a Greek prefix (di, tri etc.) between the “e” and “oic acid”

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• When a carboxyl group is bonded to a ring:1) The ring carbon bonded to the –CO2H group is

considered C12) The ending is “-carboxylic acid”

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Problems

1) Name the following molecules using common nomenclature

2) Name the following molecules using IUPAC nomenclature

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3) Draw 1,2,4-benzenetricarboxylic acid

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Structure and Physical Properties

• The carbonyl oxygen is the oxygen involved with the C=O double bond

• The carboxylate oxygen is the oxygen involved with the C-O single bond

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Structure and Physical Properties

• Carboxylic acids have relatively high boiling points– Polarity– Hydrogen bonding

• Many are water soluble14

IR Spectroscopy• Carboxylic acids have two characteristics in IR spectroscopy that

make them easy to identify– C=O stretch: 1710 cm-1 (as the dimer)– O-H stretch: 2400-3600 cm-1 (very broad)

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NMR Spectroscopy

• O-H: 9-13 (broad)

1620.3 Spectroscopy of Carboxylic Acids

Problem

• Compound X, C4H8O3, has infrared absorptions at 1710 and 2500-3100 cm-1 and has the 1H NMR spectrum shown below. Propose a structure for X.

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