Penta-2,3-dienedioic acid (one of two chemicals called glutinic acid), is an

allene In organic chemistry, allenes are organic compounds in which one carbon atom has double bonds with each of its two adjacent carbon atoms (, where R is hydrogen, H or some organyl group). Allenes are classified as diene#Classes, cumulated dienes ...

-containing

dicarboxylic acid In organic chemistry, a dicarboxylic acid is an organic compound containing two carboxyl groups (). The general molecular formula for dicarboxylic acids can be written as , where R can be aliphatic or aromatic.Boy Cornils, Peter Lappe "Dicarbox ...

. It was the first allene to be synthesized, in 1887, but the structure of it was thought to be a

propyne Propyne (methylacetylene) is an alkyne with the chemical formula . It is a component of MAPD gas—along with its isomer propadiene (allene), which was commonly used in gas welding. Unlike acetylene, propyne can be safely condensed.Peter Pä ...

core instead of an allene. The correct

structural isomer In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is a compound that contains the same number and type of atoms, but with a different connectivity (i.e. arrangement of bonds) between them. The ...

ic identity was not determined until 1954. Glutinic acid, a substituted

, was isolated from ''

Alnus glutinosa ''Alnus glutinosa'', the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family (biology), family Betulaceae, native plant, native to most of Europe, southwest Asia and northern Africa. ...

'' (Betulaceae).

Literature confusion

A diterpene, chemical name (4a''R'',5''S'',6''R'',8a''R'')-5- ''Z'')-4-carboxy-3-methylbut-3-enyl5,6,8a-trimethyl-3,4,4a,6,7,8-hexahydronaphthalene-1-carboxylic acid (), is also called ''glutinic acid''. Some database entries for "glutinic acid" incorrectly identify it as this

diterpene Diterpenes are a class of terpenes composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being a primary ...

rather than the allene meaning in the underlying publications.See patents listed for

References

Enoic acids Dicarboxylic acids Substances discovered in the 19th century Cumulated dienes {{OrganicAcid-stub