Chapter 16 - Aldehydic and Ketonic Monocarboxylic Acids and Related Compounds

Abstract

Aliphatic monocarboxylic acids containing an additional carbonyl group in the carbon chain are known generically as oxo-carboxylic acids. They are conveniently divided into two main classes depending on the position of the carbonyl group. When this occupies a terminal position, the acid is an aldehydic acid or aldocarboxylic acid, whereas when the carbonyl group is in a nonterminal position the acid is a ketonic acid or ketomonocarboxylic acid. This chapter discusses various methods of preparation, properties, typical reactions, and characteristics of saturated aldocarboxylic acids, unsaturated aldocarboxylic acids, saturated ketocarboxylic acids, and unsaturated ketocarboxylic acids along with their derivatives citing individual examples. Oxocarboxylic acids, in which the oxo group is replaced by the diazo group are called diazocarboxylic acids. The acids themselves are unstable, but their esters, especially ethyl diazoacetate, are amongst the most important aliphatic diazo compounds and are extremely useful reagents. In the β-keto-acids the ketone group is separated from the carboxyl group by one carbon atom and the resultant compounds are very unstable both in the free state and as salts. Keten dimers change on heating into trimers and higher oligomers, the reaction being facilitated by the use of basic catalysts.