Chapter 20 The Chemistry of Carboxylic Acids

Carboxylic Acids General structure: Characteristic functional group is called the carboxy group Nomenclature of Carboxylic Acids

3 Acetic acidButyric acidCaproic acid Palmitic acid

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Common Nomenclature Change the “-yl” (or “-oyl”) of the acyl group to “ic acid” 5 Acetyl group

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More Complicated Common Nomenclature Dicarboxylic acids 7 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” 9

When a carboxyl group is bonded to a ring: 1)The ring carbon bonded to the –CO 2 H group is considered C1 2)The ending is “-carboxylic acid” 10

Problems 1)Name the following molecules using common nomenclature 2)Name the following molecules using IUPAC nomenclature 11

3)Draw 1,2,4-benzenetricarboxylic acid 12

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 13

Structure and Physical Properties Carboxylic acids have relatively high boiling points – Polarity – Hydrogen bonding Many are water soluble 14

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: cm -1 (very broad) 15

NMR Spectroscopy O-H:  9-13 (broad) Spectroscopy of Carboxylic Acids

Problem Compound X, C 4 H 8 O 3, has infrared absorptions at 1710 and cm -1 and has the 1 H NMR spectrum shown below. Propose a structure for X. 17