Covers the classification of hydroxycarboxylic acids into mono- and polyhydroxy types, their chain, position and optical isomerism, and their solubility and acidity, comparing lactic and propionic acid pKa values. It then describes reactions of the hydroxyl and carboxyl groups, oxidation, and heating products such as lactide. Representatives are treated in turn, including carbonic, lactic, hydroxybutyric, ricinoleic, salicylic, malic, citric and tartaric acids, with the citric acid cycle steps and tartaric acid stereoisomers set out.
Topic 31 of 47 in the MU Pleven syllabus for Chemistry (Medicine, Year 1). The free AceMed note covers it in 5 sections, about 2,041 words (14 min of reading), with 14 flashcards.
Hydroxy acids are one family of substituted carboxylic acids. A hydroxy acid is a carboxylic acid with one or more extra hydroxyl groups. Depending on the number of carboxylic and hydroxyl groups there are:
Monohydroxymonocarboxylic acids:
HO-R-COOH (aliphatic hydroxy acids)
HO-Ar-COOH (aromatic hydroxy acids)
Polyhydroxypolycarboxylic acids:
(HO)m R (COOH)n (aliphatic hydroxy acids)
(HO)m Ar(COOH)n (aromatic hydroxy acids)
II. ISOMERISM
1. Chain isomerism.
The long-chain carboxylic acids may be with a normal carbon chain, or a branched carbon chain. The carboxylic acids with a branched carbon chain are very often called isocarboxylic acids.
2. Position isomerism.
Hydroxycarboxylic acids, which have the same carbon skeleton, but differ in the position occupied by a hydroxyl group, are called positional isomers. Greek letters are often used instead of numbers in the common names of substituted carboxylic acids to designate the location of substituents. For example:
3. Optical isomerism.
Hydroxycarboxylic acids, containing chiral carbon atom, are optically active substances. Such hydroxy acids are -hydroxyvaleric acid, -hydroxy- -methylbutyric acid, -hydroxybutyric acid and -hydroxybutyric acid.
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