Crotonic acid

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Crotonic acid
Skeletal formula of crotonic acid
Ball-and-stick model of the crotonic acid molecule
Names
Preferred IUPAC name
(2E)-But-2-enoic acid
Other names
(E)-But-2-enoic acid
(E)-2-Butenoic acid
Crotonic acid
trans-2-Butenoic acid
β-Methylacrylic acid
3-Methylacrylic acid
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.003.213 Edit this at Wikidata
UNII
  • InChI=1S/C4H6O2/c1-2-3-4(5)6/h2-3H,1H3,(H,5,6)/b3-2+ checkY
    Key: LDHQCZJRKDOVOX-NSCUHMNNSA-N checkY
  • InChI=1/C4H6O2/c1-2-3-4(5)6/h2-3H,1H3,(H,5,6)/b3-2+
    Key: LDHQCZJRKDOVOX-NSCUHMNNBH
  • C/C=C/C(O)=O
  • O=C(O)/C=C/C
Properties
C4H6O2
Molar mass 86.090 g·mol−1
Density 1.02 g/cm3
Melting point 70 to 73 °C (158 to 163 °F; 343 to 346 K)
Boiling point 185 to 189 °C (365 to 372 °F; 458 to 462 K)
Acidity (pKa) 4.69 [1]
Hazards
Safety data sheet (SDS) SIRI.org
Related compounds
Other anions
crotonate
pentanoic acid
tetrolic acid
Related compounds
2-butanone
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Crotonic acid ((2E)-but-2-enoic acid) is a short-chain

cis-alkene, Isocrotonic acid is an isomer of crotonic acid. Crotonic acid is soluble in water and many organic solvents. Its odor is similar to that of butyric acid
.

Production

Crotonic acid produced industrially by oxidation of crotonaldehyde:[3][4]: 230 

CH3CH=CHCHO + 1/2 O2 → CH3CH=CHCO2H

A number of other methods exist, including the Knoevenagel condensation of acetaldehyde with malonic acid in pyridine:[3]: 229 

Synthesis of crotonic acid by the Knoevenagel condensation of acetaldehyde and malonic acid

The alkaline hydrolysis of allyl cyanide followed by the intramolecular rearrangement of the double bond:[5][6]

Alkaline hydrolysis of allyl cyanide

Furthermore, it is formed during the

3-hydroxybutyric acid:[7]

Synthesis of crotonic acid from 3-hydroxybutyric acid

Properties

Crotonic acid crystallizes in the

lattice parameters a = 971 pm, b = 690 pm, c = 775 pm and β = 104.0°. The unit cell contains four formula units.[8]

Reactions

Crotonic acid converts into butyric acid by hydrogenation or by reduction with zinc and sulfuric acid.[9]

Hydrogenation of crotonic acid

Upon treatment with chlorine or bromine, crotonic acid converts to 2,3-dihalobutyric acids:[9]

Chlorination of butenoic acid

Crotonic acid adds hydrogen bromide to form 3-bromobutyric acid.[9][10]

Reaction of crotonic acid with hydrogen bromide.

The reaction with alkaline potassium permanganate solution affords 2,3-dihydroxybutyric acid.[9]

Reaction of crotonic acid with alkaline potassium permanganate solution.

Upon heating with acetic anhydride, crotonic acid converts to the acid anhydride:[11]

Esterification
of crotonic acid using sulfuric acid as a catalyst provides the corresponding crotonate esters:

Preparation of crotonate esters.

Crotonic acid reacts with hypochlorous acid to 2-chloro-3-hydroxybutyric acid. This can either be reduced with sodium amalgam to butyric acid, can form with sulfuric acid 2-chlorobutenoic acid, react with hydrogen chloride to 2,3-dichlorobutenoic acid or with potassium ethoxide to 3-methyloxirane-2-carboxylic acid.[12]

Reaction of crotonic acid into 2-chloro-3-hydroxybutanoic acid and subsequent reactions

Crotonic acid reacts with ammonia at the alpha position in the presence of mercury(II) acetate. This reaction provides DL-threonine.[13]

Use

Crotonic acid is mainly used as a comonomer with vinyl acetate.[14] The resulting copolymers are used in paints and adhesives.[4]

Crotonyl chloride reacts with N-ethyl-2-methylaniline (N-ethyl-o-toluidine) to provide crotamiton, which is used as an agent against scabies.[15]

Crotamiton synthesis
Crotamiton synthesis

Safety

Its LD50 is 1 g/kg (oral, rats).[4] It irritates eyes, skin, and respiratory system.[14]

See also

References

  1. ^ Dawson, R. M. C.; et al. (1959). Data for Biochemical Research. Oxford: Clarendon Press.
  2. ^ Chisholm, Hugh, ed. (1911). "Crotonic Acid" . Encyclopædia Britannica. Vol. 7 (11th ed.). Cambridge University Press. p. 511.
  3. ^
    ISBN 3-7776-0406-2
    .
  4. ^
    ISBN 978-3527306732
    .
  5. doi:10.1002/jlac.18711590110
    .
  6. doi:10.1002/jlac.19073510127
    .
  7. ^ Beilstein, F. (1893). Handbuch der organischen Chemie (in German). Vol. 1 (3rd ed.). Verlag Leopold Voss. p. 506.
  8. doi:10.1246/bcsj.47.1627
    .
  9. ^ a b c d Heilbron (1953). "Crotonic acid". Dictionary of Organic Compounds. 1: 615.
  10. doi:10.1002/cber.19150480205
    .
  11. American Chemical Journal
    . 29 (3): 179–203.
  12. ^ Beilstein, F. (1893). Handbuch der organischen Chemie (in German). Vol. 1 (3rd ed.). Verlag Leopold Voss. p. 562.
  13. ^ Carter, H. E.; West, H. D. (1955). "dl-Threonine". Organic Syntheses; Collected Volumes, vol. 3, p. 813.
  14. ^ a b Entry on Butensäuren. at: Römpp Online. Georg Thieme Verlag, retrieved January 7, 2020.
  15. ISBN 3-13-558402-X
    .
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