Mesoxalic acid, also called oxomalonic acidorketomalonic acid, is an organic compound with formula C3H2O5 or HO−(C=O)3−OH.
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| Preferred IUPAC name
Oxopropanedioic acid | |
| Other names
Ketomalonic acid | |
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| ECHA InfoCard | 100.006.796 
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| Properties | |
| C3H2O5 | |
| Molar mass | 118.045 g/mol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Mesoxalic acid is both a dicarboxylic acid and a ketonic acid. It readily loses two protons to yield the divalent anion C3O2−5, called mesoxalate, oxomalonate, or ketomalonate. These terms are also used for salts containing this anion, such as sodium mesoxalate, Na2C3O5; and for esters containing the −C3O5− or −O−(C=O)3−O− moiety, such as diethyl mesoxalate, (C2H5)2C3O5. Mesoxalate is one of the oxocarbon anions, which (like carbonate CO2−3 and oxalate C2O2−4) consist solely of carbon and oxygen.
Mesoxalic acid readily absorbs and reacts with water to form a product commonly called "mesoxalic acid monohydrate", more properly dihydroxymalonic acid, HO−(C=O)−C(OH)2−(C=O)−OH.[2] In product catalogs and other contexts, the terms "mesoxalic acid", "oxomalonic acid" and so on often refer to this "hydrated" compound. In particular, the product traded as "sodium mesoxalate monohydrate" is almost always sodium dihydroxymalonate.
Mesoxalic acid can be obtained synthetically by hydrolysisofalloxan with baryta water,[2] by warming caffuric acid[3] with lead acetate solution,[2] or from glyceryl diacetate and concentrated nitric acid in ice-cold water. The product can be obtained also by oxidation of tartronic acid[4]orglycerol.[5] Since they are carried out in water, these procedures generally give the dihydroxy derivative.
It is also prepared by the oxidation of glycerol with the help of bismuth(III) nitrate.
