Cinnamic acid
- 3- phenylacrylic
- Trans-3- phenylpropenoic acid
- (E )-3- phenylpropenoic acid
- Trans-cinnamic acid
- (E)- cinnamic acid
- FEMA 2288
- 621-82-9
- 140-10-3 (trans- cinnamic acid )
- 102-94-3 (cis- cinnamic acid )
White crystals with a characteristic odor
Fixed
1.25 g · cm -3
134 ° C
Decomposition ( decarboxylation to styrene )
4.44
- Poorly in water ( 0.5 g · l-1 at 20 ° C)
- Well in many organic solvents
Trans-
Attention
Template: Infobox chemical / molecular formula search available
Cinnamic acid ( trans-3- phenylacrylic, FEMA 2288 ) is a white solid with a characteristic odor. Cinnamic acid occurs in some plants from natural and non-toxic. In addition to cinnamaldehyde and eugenol is an important component of cinnamon. Cinnamic acid is one of the aromatic compounds and is an unsaturated carboxylic acid with a trans -substituted carbon-carbon double bond in the side chain. The isomeric cis- cinnamic acid ( Allozimtsäure ) has only minor importance. The information in this article applies only to the trans-cinnamic acid.
Representation
Cinnamic acid can be prepared from benzaldehyde, for example via the aldol reaction with malonic acid ( Doebner variant).
A specially developed for the cinnamic acid pathway is the Perkin reaction:
Another synthetic route via aldol condensation of benzaldehyde and acetaldehyde.
Cinnamic acid is also produced by the already held in the air oxidation of cinnamaldehyde.
Properties
Physical Properties
Cinnamic acid crystallizes in the monoclinic crystal system, space group P21 / n and the lattice parameters a = 779 pm, b = 1807 pm, c = 567 pm, and β = 97 °. In the unit cell contains four formula units. It is known by the β - and γ - modification, two further metastable forms. The crystal structure of the β - modification is isomorphic to 4- chlorocinnamic.
Chemical Properties
On distillation at 146 ° C and about 4 hPa decomposition takes place by decarboxylation to styrene.
Biosynthesis
Cinnamic acid is formed from the amino acid L -phenylalanine, in the course of deamination by the phenylalanine ammonia-lyase ( EC 4.3.1.24 ) is deaminated in an analogous reaction the amino acid L- tyrosine to the para - coumaric acid (4- hydroxycinnamic acid ). It is an intermediate in the biosynthesis of chalcones (and thus the flavonoid precursor ) and stilbenes.
Use and Reactivity
Cinnamic acid can be used for the preparation of phenylacetylene. Some of their esters as fragrances in application. During UV irradiation of trans-cinnamic acid isomerization causes the formation of cis- cinnamic acid ( Allozimtsäure ):
Photochemical dimerization of cinnamic acid to form a cyclobutane ring. Depending on the crystal form of this results in two different isomers. From the α - polymorph is α - Truxillsäure arises. The β - polymorph forms the β - truxinic. The γ - polymorph can not be photochemically dimerized.
Derivatives
On the phenyl ring by a hydroxy -substituted derivatives belonging to the group of phenolic acids. Sinapic acid (3,5- dimethoxy-4- hydroxycinnamic acid ) and α - cyano-4- hydroxycinnamic acid ( HCCA ), suitable organic matrix in MALDI -MS (Matrix Assisted Laser Desorption Ionization Mass Spectrometry ) is used. These include, for example, ferulic acid and caffeic acid.
The reaction with thionyl chloride ( SOCl2 ) cinnamic acid is converted to the reactive cinnamyl chloride.
By esterification with ethanol in the presence of sulfuric acid or hydrochloric acid as a catalyst, the flavor can be obtained ethyl cinnamate.