Allocinnamic acid is a ''cis''-isomer of

cinnamic acid Cinnamic acid is an organic compound with the formula phenyl, C6H5-CH=CH-Carboxylic acid, COOH. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Classified as an unsaturated carboxy ...

, into which the cinnamic acid is easily converted.

Synthesis

Allocinnamic acid was first discovered by Сarl Liebermann in 1890 in coca leaves, then Liebermann found that this acid is formed during the reduction (by zinc dust in an alcoholic solution during boiling) of ''β''-dibromopropiolic acid.

Physical properties

Allocinnamic acid crystallizes in the form of three crystalline modifications with melting points of 68 °C, 58 °C, and 42 °C. It is hardly soluble in water and cold

ligroin Ligroin is the petroleum fraction consisting mostly of C7 and C8 hydrocarbons and boiling in the range 90‒140 °C (194–284 °F). The fraction is also called heavy naphtha. Ligroin is used as a laboratory solvent. Products under the name ...

, easily soluble in alcohol and ether, and does not change in dim light.

Chemical properties

When heated briefly with concentrated

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, the compound turns into cinnamic acid.{{cite book , title=Quarterly Journal of the Chemical Society of London , date=1890 , publisher=Chemical Society (Great Britain) , page=1417 , url=https://books.google.com/books?id=rALzAAAAMAAJ&dq=Allocinnamic+acid++sulfuric+acid,&pg=PA1417 , access-date=13 June 2025 , language=en It forms liquid anhydride with

acetic anhydride Acetic anhydride, or ethanoic anhydride, is the chemical compound with the chemical formula, formula . Commonly abbreviated , it is one the simplest organic acid anhydride, anhydrides of a carboxylic acid and is widely used in the production of c ...

, which turns into cinnamic acid anhydride when heated.

References

Aromatic acids Phenylpropanoids