A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Page
GO
GO
?
^
Top
Org. Synth. 1944, 24, 92
DOI: 10.15227/orgsyn.024.0092
SORBIC ACID
Submitted by C. F. H. Allen and J. VanAllan.
Checked by C. S. Hamilton and R. A. Alberty.
1. Procedure
A mixture of 80 g. (93.2 ml., 1.14 moles) of crotonaldehyde (b.p. 102–103°), 120 g. (1.15 moles) of malonic acid (m.p. 134–135°), and 120 g. (122 ml., 1.52 moles) of pyridine (b.p. 113–115°) is heated for 3 hours in a 1-l. flask on a steam bath under a reflux condenser. At the end of this period the evolution of carbon dioxide will have practically ceased. The flask and contents are then cooled in ice, and a solution of 42.5 ml. (0.76 mole) of concentrated sulfuric acid in 100 ml. of water is added with shaking. Most of the sorbic acid separates at once; the remainder is obtained by chilling the solution in an ice bath for 3 hours. The crude acid is filtered by suction and washed once with a small amount of ice water; it is recrystallized at once from 250 ml. of boiling water. The purified acid, which separates on standing overnight in the ice chest, is filtered; it melts at 134°. The yield is 36–41 g. (28–32%) (Note 1), (Note 2), and (Note 3).
2. Notes
1. The submitters have found that the percentage yield is the same when double the above quantities are used.
2. This is an example of a general reaction. If acetic acid is used as a solvent, the substituted malonic acids can be secured, whereas organic bases facilitate the loss of carbon dioxide. The product is generally a mixture from which but a single substance can be isolated.
3. The use of simple aldehydes gives better yields of unsaturated acids; this is especially noticeable when aromatic aldehydes are employed.1 Mixtures of α,β- and β,γ-unsaturated acids have been reported when aliphatic aldehydes and certain basic catalysts are used.2,3
3. Discussion
Sorbic acid has been prepared from crotonaldehyde4 or aldol5 and malonic acid in pyridine solution; by hydrogen peroxide oxidation of the condensation product of crotonaldehyde and pyruvic acid;6 and by the action of alkali on 3-hydroxy-4-hexenoic acid,7,8 β,δ-disulfo-n-caproic acid,9 parasorbic acid,10,11 and 3,5-hexadienoic acid.12

References and Notes
  1. K. A. Pandya and R. B. Pandya, Proc. Indian Acad. Sci., 14A, 112 (1941) [C. A., 36, 1599 (1942)].
  2. Auwers, Ann., 432, 58 (1923).
  3. Boxer and Linstead, J. Chem. Soc., 1931, 740.
  4. Doebner, Ber., 33, 2140 (1900).
  5. Riedel, Ann., 361, 90 (1908).
  6. Smedley and Lubrzynska, Biochem. J., 7, 370 (1913).
  7. Jaworski, J. Russ. Phys. Chem. Soc., 35, 274 (1903) [Chem. Zentr., 1903, II, 555].
  8. Jaworski and Reformatski, Ber., 35, 3636 (1902).
  9. Notebohn, Ann., 412, 77 (1916).
  10. Hofmann, Ann., 110, 132 (1859).
  11. Doebner, Ber., 27, 351 (1894).
  12. Paul and Tchelitcheff, Bull. soc. chim. France, 1948, 108.

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

aldol

parasorbic acid

sulfuric acid (7664-93-9)

acetic acid (64-19-7)

carbon dioxide (124-38-9)

pyridine (110-86-1)

hydrogen peroxide (7722-84-1)

Malonic acid (141-82-2)

Pyruvic acid (127-17-3)

crotonaldehyde (123-73-9)

Sorbic acid (110-44-1)

3-hydroxy-4-hexenoic acid

3,5-hexadienoic acid

β,δ-disulfo-n-caproic acid