Cinnamic acid
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| Names | |
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| Preferred IUPAC name
(2E)-3-Phenylprop-2-enoic acid | |
| Other names
Cinnamic acid trans-Cinnamic acid Phenylacrylic acid[1] Cinnamylic acid 3-Phenylacrylic acid (E)-Cinnamic acid Benzenepropenoic acid Isocinnamic acid | |
| Identifiers | |
| 3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.004.908 |
| KEGG | |
| PubChem CID |
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| UNII | |
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| Properties | |
| C9H8O2 | |
| Molar mass | 148.16 g·mol−1 |
| Appearance | White monoclinic crystals |
| Density | 1.2475 g/cm3[2] |
| Melting point | 133 °C (271 °F; 406 K)[2] |
| Boiling point | 300 °C (572 °F; 573 K)[2] |
| 500 mg/L[2] | |
| Acidity (pKa) | 4.44 |
| -78.36·10−6 cm3/mol | |
| Hazards | |
| EU classification (DSD) (outdated) |
Irritant (Xi) |
| R-phrases (outdated) | R36 |
| S-phrases (outdated) | S25 |
| NFPA 704 | |
| Flash point | > 100 °C (212 °F; 373 K)[2] |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is  ?) | |
| Infobox references | |
Cinnamic acid is an organic compound with the formula C6H5CHCHCO2H. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents.[3] Classified as an unsaturated carboxylic acid, it occurs naturally in a number of plants. It exists as both a cis and a trans isomer, although the latter is more common.[4]
Occurrence and production
Natural occurrence
It is obtained from oil of cinnamon, or from balsams such as storax.[5] It is also found in shea butter. Cinnamic acid has a honey-like odor;[6] it and its more volatile ethyl ester (ethyl cinnamate) are flavor components in the essential oil of cinnamon, in which related cinnamaldehyde is the major constituent. Cinnamic acid is also part of the biosynthetic shikimate and phenylpropanoid pathways. Its biosynthesis is performed by action of the enzyme phenylalanine ammonia-lyase (PAL) on phenylalanine.
Production
The original synthesis of cinnamic acid involves the Perkin reaction, which entails the base-catalysed condensation of acetic anhydride and benzaldehyde. Rainer Ludwig Claisen (1851–1930) described the synthesis of cinnamate esters by the reaction of benzaldehyde and esters.[7] The reaction is known as the Aldol condensation (with accompanying hydrolysis of the anhydride).
Synthesis of cinnamic acid via Perkin reaction
It can also be prepared from cinnamaldehyde and benzal chloride.[4]
Another way of preparing Cinnamic acid is by the Knövenaegel–Hans condensation reaction.[8] The reactants for this are the corresponding benzaldehyde and malonic acid in the presence of a weak base, followed by acid hydrolysis.
Uses
Cinnamic acid is used in flavors, synthetic indigo, and certain pharmaceuticals. A major use is in the manufacturing of the methyl, ethyl, and benzyl esters for the perfume industry.[5] Cinnamic acid is a precursor to the sweetener aspartame via enzyme-catalysed amination to phenylalanine.[4] Cinnamic acid can dimerize in non-polar solvents resulting in different linear free energy relationships[9]
References
- ↑
"Cinnamic Acid". Encyclopædia Britannica. 6 (11th ed.). 1911. p. 376. - 1 2 3 4 5 Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
- ↑ "Open Notebook Science Challenge: Solubilities of Organic Compounds in Organic Solvents". Nature Precedings. 2010. doi:10.1038/npre.2010.4243.3.
- 1 2 3 Dorothea Garbe "Cinnamic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a07_099
- 1 2 Budavari, Susan, ed. (1996), The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (12th ed.), Merck, ISBN 0911910123
- ↑ Cinnamic acid, flavornet.org
- ↑ Claisen, L. (1890) "Zur Darstellung der Zimmtsäure und ihrer Homologen" (On the preparation of cinnamic acid and its homologues), Berichte der deutschen chemischen Gesellschaft, 23 : 976–978.
- ↑ L. Tieze, Reactions and Synthesis in the Organic Chemistry Laboratory, Mill Vall, California, 1988, p. 1988.
- ↑ J-C Bradley et al., “Determination of Abraham model solute descriptors for the monomeric and dimeric forms of trans-cinnamic acid using measured solubilities from the Open Notebook Science Challenge”, Chemistry Central Journal 9:11 (2015)