{{Chembox <!-- Images --> | Name = Allocinnamic acid | ImageFile = Аллокоричная кислота.svg | ImageSize = 100px | ImageAlt = <!-- Names --> | IUPACName = (''Z'')-3-phenylprop-2-enoic acid | OtherNames = ''cis''-''β''-carboxystyrene, ''cis''-cinnamic acid; | Section1 = {{Chembox Identifiers | CASNo = 102-94-3 | CASNo_Ref = {{Cascite|correct|CAS}} | ChemSpiderID = 10286933 | DTXSID = DTXSID001019000 | EC_number = 827-073-9 | ChEBI = 35699 | ChEMBL = | Gmelin = 279588 | KEGG = | UNII = YB7ZGY8NE2 | PubChem = 5372954 | InChI = InChI=1S/C9H8O2/c10-9(11)7-6-8-4-2-1-3-5-8/h1-7H,(H,10,11)/b7-6- | InChIKey = WBYWAXJHAXSJNI-SREVYHEPSA-N | SMILES = C1=CC=C(C=C1)C=CC(=O)O }} | Section2 = {{Chembox Properties | H=8|O=6|C=9 | MolarMass = | Appearance = colorless crystals | Density = 1.49 g/cm³ | MeltingPtC = 68 | BoilingPtC = 265 | BoilingPt_ref = | Solubility = soluble }} | Section3 = {{Chembox Hazards | GHSPictograms = | GHSSignalWord = | GHS_ref = | HPhrases = | PPhrases = | MainHazards = | FlashPt = | AutoignitionPt = }} }} '''Allocinnamic acid''' is a ''cis''-isomer of cinnamic acid, into which the cinnamic acid is easily converted.<ref>{{cite web |last1=Informatics |first1=NIST Office of Data and |title=(Z)-3-Phenyl-2-propenoic acid |url=https://webbook.nist.gov/cgi/cbook.cgi?ID=C102943 |publisher=NIST |access-date=13 June 2025 |language=en}}</ref><ref>{{cite book |last1=Senning |first1=Alexander |title=Elsevier's Dictionary of Chemoetymology: The Whys and Whences of Chemical Nomenclature and Terminology |date=30 October 2006 |publisher=Elsevier |isbn=978-0-08-048881-3 |page=14 |url=https://books.google.com/books?id=Fl4sdCYrq3cC&dq=Allocinnamic+acid&pg=PA14 |access-date=13 June 2025 |language=en}}</ref>
==Synthesis== Allocinnamic acid was first discovered by Carl Liebermann in 1890 in coca leaves,<ref name="QJ"/><ref>{{cite book |last1=Gattermann |first1=Ludwig |title=The Practical Methods of Organic Chemistry |date=1896 |publisher=Macmillan |page=268 |url=https://books.google.com/books?id=IR2-Lhipf30C&dq=Allocinnamic+acid&pg=PA268 |access-date=13 June 2025 |language=en}}</ref> 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.<ref>{{cite book |last1=Whitmore |first1=Frank C. |title=Organic Chemistry, Volume Two: Part III: Aromatic Compounds Part IV: Heterocyclic Compounds Part V: Organophosphorus and Organometallic Compounds |date=14 December 2011 |publisher=Courier Dover Publications |isbn=978-0-486-60701-6 |page=703 |url=https://books.google.com/books?id=jgZLDwAAQBAJ&dq=Allocinnamic+acid++sulfuric+acid,&pg=PA703 |access-date=13 June 2025 |language=en}}</ref><ref>{{cite book |title=Ullmann's Fine Chemicals |date=7 January 2014 |publisher=John Wiley & Sons |isbn=978-3-527-68359-8 |url=https://books.google.com/books?id=yZqOAgAAQBAJ&dq=Allocinnamic+acid&pg=PA427 |access-date=13 June 2025 |language=en}}</ref> It is hardly soluble in water and cold ligroin, easily soluble in alcohol and ether, and does not change in dim light.<ref>{{cite journal |last1=Lee |first1=Ho-Hi |last2=Senda |first2=Hitoshi |last3=Kuwae |first3=Akio |last4=Hanai |first4=Kazuhiko |title=Crystal and Molecular Structures of Allocinnamic Acid |journal=Bulletin of the Chemical Society of Japan |date=1 May 1994 |volume=67 |issue=5 |pages=1475–1478 |doi=10.1246/bcsj.67.1475 |url=https://academic.oup.com/bcsj/article-abstract/67/5/1475/7349270?redirectedFrom=fulltext |access-date=13 June 2025|url-access=subscription }}</ref>
==Chemical properties== When heated briefly with concentrated sulfuric acid, the compound turns into cinnamic acid.<ref name="QJ">{{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}}</ref>
It forms liquid anhydride with acetic anhydride, which turns into cinnamic acid anhydride when heated.
== References == <references/>
Category:Aromatic acids Category:Phenylpropanoids