Beta hydroxycarboxylic acid

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3-Hydroxypropionic acid, a simple beta hydroxy acid

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.[1]


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
Propanoic acid 4.87[2]
α-Hydroxypropionic acid 3.86[3]
β-Hydroxypropionic acid 4.51[2]

Other beta hydroxy acids include:

See also[edit]


  1. ^ Miltenberger, Karlheinz (2000). "Hydroxycarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_507. ISBN 978-3527306732.
  2. ^ a b Handbook of Chemistry and Physics, CRC press, 58th edition page D150-151 (1977)
  3. ^ Dawson, R. M. C. et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.