title: Butenoic acid
text: # Butenoic acid
  
  Butenoic acid is any of three monocarboxylic acids with an unbranched 4-carbon chain with 3 single bonds and one double bond; that is, with the structural formula HO(O=)C–CH=CH–CH $_2–H$ (2-butenoic) or HO(O=)C–CH $_2–CH=CH–H$ (3-butenoic). All have the chemical formula C $_3H$ $_5COOH$ or C $_4H$ $_6O$ $_2.$
  
  These compounds are technically mono-unsaturated fatty acids, although some authors may exclude them for being too short. The three isomers are:
  
  * crotonic acid (trans-2-butenoic or (2E)-but-2-enoic acid)
  * isocrotonic acid (cis-2-butenoic or (2Z)-but-2-enoic acid)
  * 3-butenoic acid (but-3-enoic acid).
  