Beta hydroxycarboxylic acid should not be confused with butylated hydroxyanisole.
A beta hydroxy carboxylic acid or β-hydroxy carboxylic acid (BHA) is a carboxylic acid containing a hydroxy functional group separated by two carbon atoms. They are related to alpha hydroxy acids, in which the two functional groups are separated by only one carbon atom.
Upon dehydration, beta-hydroxy acids yield an alpha-beta unsaturated acid.
Compared to their non-hydroxylated counterpart, beta hydroxy carboxylic acids are stronger, although weaker than the alpha hydroxy acids. Due to the larger distance, the intramolecular hydrogen bridge is less easily formed compared to the alpha hydroxy acids. The table summarizes some values on the propionic series.
| Name | pKa | |
|---|---|---|
| 4.87[1] | ||
| 3.86[2] | ||
| 4.51 |
Other beta hydroxy acids include: