Piperic acid
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 416140319
| ImageFile1 = Piperinsäure.svg
| PIN = (2E,4E)-5-(2H-1,3-Benzodioxol-5-yl)penta-2,4-dienoic acid
|Section1={{Chembox Identifiers
| CASNo = 136-72-1
| CASNo_Ref = {{cascite|correct|??}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = GFG3FLA9UR
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 37316
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 332122
| EINECS = 226-118-4
| PubChem = 5370536
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 4521337
| SMILES = C1OC2=C(O1)C=C(C=C2)/C=C/C=C/C(=O)O
| InChI = 1/C12H10O4/c13-12(14)4-2-1-3-9-5-6-10-11(7-9)16-8-15-10/h1-7H,8H2,(H,13,14)/b3-1+,4-2+
| InChIKey = RHBGITBPARBDPH-ZPUQHVIOBF
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/C12H10O4/c13-12(14)4-2-1-3-9-5-6-10-11(7-9)16-8-15-10/h1-7H,8H2,(H,13,14)/b3-1+,4-2+
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = RHBGITBPARBDPH-ZPUQHVIOSA-N
| RTECS =
| MeSHName = C017637
}}
|Section2={{Chembox Properties
| C=12 | H=10 | O=4
| Density =
| MeltingPtC =
| BoilingPt = decomposes
| pKa =
}}
}}
Piperic acid is a chemical often obtained by the base-hydrolysis of the alkaloid piperine{{cite book | url = https://books.google.com/books?id=iyzlMSPp-EMC&pg=PA327 | page = 327 | isbn = 978-0-470-74167-2 | author = Paul M. Dewick. | year = 2009 | publisher = A John Wiley & Sons | location = Chichester | title = Medicinal natural products : a biosynthetic approach }} from black pepper,{{cite book | title = The Volatile Oils| volume = 1 | author = E. Gildemeister | url = http://chestofbooks.com/health/aromatherapy/The-Volatile-Oils-Vol1/Heliotropin.html}} followed by acidification of the corresponding salt. Piperic acid is an intermediate in the synthesis of other compounds such as piperonal, and as-such may be used to produce fragrances, perfumes flavorants and drugs as well as other useful compounds.
Preparation
Piperic acid can be prepared from the commercially-available alkaloid piperine, a cyclic amide containing a piperidine group, by reacting it with a hydroxide such as potassium hydroxide, then acidifying the formed piperate salt with hydrochloric acid or another acid. The toxic compound piperidine is given off during the base-hydrolysis of piperine and as-such, safety precautions should be taken.
Reactions
Reaction of piperic acid with strong oxidizers such as potassium permanganate or ozone, or a halogen such as bromine followed by sodium hydroxide causes oxidative cleavage of the double-bonds, yielding piperonal and piperonylic acid.{{Cite patent | country = US | title = Preparation process for piperonal | number = 5095128 }} Piperonal has many uses in industry and is itself a precursor to a good subsection of other chemicals. On reduction with sodium amalgam piperic acid forms α- and β-dihydropiperic acid, C12H12O4, and the latter can take up two further atoms of hydrogen to produce tetrahydropiperic acid.