Truxillic acids are any of several crystalline stereoisomeric cyclic dicarboxylic acids with the formula (C6H5C2H2(CO2H)2. They are colorless solids. These compounds are obtained by the [2 + 2] photocycloadditions of cinnamic acid where the two trans alkenes react head-to-tail. The isolated stereoisomers are called truxillic acids.[1] The preparation of truxillic acids provided an early example of organic photochemistry.[2]
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IUPAC name
7,8′-Cyclo-8,7′-neolignane-9,9′-dioic acid
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Systematic IUPAC name
2,4-Diphenylcyclobutane-1,3-dicarboxylic acid | |
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3D model (JSmol)
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ChemSpider |
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ECHA InfoCard | 100.022.478 |
PubChem CID
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UNII |
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CompTox Dashboard (EPA)
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Properties | |
C18H16O4 | |
Molar mass | 296.322 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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These compounds are found in a variety of plants, for example in coca.[3][4] Incarvillateine, an alkaloid from the plant Incarvillea sinensis, is a derivative of α-truxillic acid.
Upon heating, truxillic acids undergo cracking to give cinnamic acid.[5]
Truxillic acid can exist in five stereoisomers.[6][7]
Isomer | a | b | c | d | e | f |
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α-truxillic acid (cocaic acid[8]) |
COOH | H | H | C6H5 | H | COOH |
γ-truxillic acid | COOH | H | H | C6H5 | COOH | H |
ε-truxillic acid | H | COOH | C6H5 | H | H | COOH |
peri-truxillic acid | COOH | H | C6H5 | H | COOH | H |
epi-truxillic acid | COOH | H | C6H5 | H | H | COOH |
Below are the five stereoisomers of truxillic acid, called alpha, gamma, epsilon, peri, and epi. These are shown both in a 2D skeletal diagram with stereocenters indicated and a 3D rendering of the structural geometry of the isomers themselves.