Pentenoic acid


Pentenoic acid is any of five mono-carboxylic acids whose molecule has an unbranched chain of five carbons connected by three single bonds and one double bond. That is, any compound with one of the formulas,, or . In the IUPAC-recommended nomenclature, these acids are called pent-2-enoic, pent-3-enoic, and pent-4-enoic, respectively. All these compounds have the empirical formula.
Pentenoic acids are technically mono-unsaturated fatty acids, although they are rare or unknown in biological lipids. A salt or ester of such an acid is called a pentenoate.

Geometric isomers

There are actually two 2-pentenoic acids, distinguished by the conformation of the two single C–C bonds adjacent to the double bond: either on the same side of the double bond's plane or on opposite sides of it.
Likewise, there are two 3-pentenoic acids. On the other hand, there is only one 4-pentenoic acid, since the two hydrogen atoms on the last carbon are symmetrically placed across the double bond's plane.
The full list of pentenoic acids is, therefore:cis-2-pentenoic or -pent-2-enoic acid.trans-2-pentenoic or -pent-2-enoic acid. MP ~10 °C; BP ~108 °C at 17 torr, ~198 °C; odor cheesy, sour. Occurs in banana, beer. Flavoring agent.cis-3-pentenoic or -pent-3-enoic acid.trans-3-pentenoic or -pent-3-enoic acid . BP ~187 °C.
  • 4-pentenoic or pent-4-enoic acid, 3-vinylpropionic acid. Dens ~0.975 at 25 °C; IoR ~1.428; MP ~ -23 °C; BP ~83 °C at 12 torr, ~188 °C; sol. water, slightly; odor cheese, mustard. Toxic.

Esters

Esters of pentenoic acids include:
  • Ethyl cis-2-pentenoate.
  • Ethyl trans-2-pentenoate BP ~150 °C.
  • Butyl 2-pentenoate.
  • Ethyl trans-3-pentenoate.
  • ethyl cis-3-pentenoate.
  • isopropyl 3-pentenoate.
  • Butyl 3-pentenoate Odor of chamomile. Flavoring agent.

Derivatives

Some derivatives of pentenoic acid include:
  • 2-Oxopent-4-enoic acid, transient species possibly produced by Azotobacter vinelandii
  • 2-Amino-5-chloro-4-pentenoic acid, found in the mushroom Amanita cokeri
  • 2-Methyl-3-pentenoic acid. Some esters are berry fruit flavors.
  • 2-Propyl-trans-2-pentenoic acid, major metabolite of anticonvulsant valproic acid.
  • cis-2-methyl-2-pentenoic acid 2-methyl--pent-2-enoic acid. BP ~214 °C. Flavoring agent.
  • trans-2-Methyl-2-pentenoic acid 2-methyl--pent-2-enoic acid. dens ~0.987; IoR ~1.46; MP ~25 °C; BP ~124 °C at 30 torr, ~214 °C; odor fruity, strawberry. Flavoring agent.
  • 2-Methyl-2-pentenoic acid, cis/''trans'' mix. Dens ~0.983 at 25 °C; IoR ~1.46; MP ~25 °C; BP ~124 °C at 30 torr, ~112 °C at 12 torr; sol. water, slightly; odor acidic, fruity, sweaty. Flavoring and perfuming agent.
  • 2-Methyl-4-pentenoic acid, 2-methyl-pent-4-enoic acid. The hexyl ester is a flavoring agent for chewing-gum, candy, beverages;.