Colourless, crystalline, toxic carboxylic acid found in many plants, especially rhubarb, wood sorrel, and spinach. Because it forms soluble chelates with iron, some of the iron in these plants is not available nutritionally. However, this property makes it useful for removing blood and rust stains, cleaning metals other than iron, and flushing car radiators. Oxalic acid and its salts (oxalates) are used in many chemical processes.
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In general, dicarboxylic acids show the same chemical behaviour and reactivity as monocarboxylic acids. The ionization of the second carboxyl group occurs less readily than the first one. This is because more energy is required to separate a positive hydrogen ion from the doubly charged anion than from the single charged anion.
A mnemonic to aid in remembering the order of the common nomenclature for the first six dicarboxylic acids is "Oh my, such great apple pie!" (oxalic, malonic, succinic, glutaric, adipic, pimelic).
When one of the carboxy groups is replaced with an aldehyde group, the resulting structure is called a "aldehydic acid".
|Common name||IUPAC name||Chemical formula||Structural formula|
|Oxalic acid||ethanedioic acid||HOOC-COOH|
|Malonic acid||propanedioic acid||HOOC-(CH2)-COOH|
|Succinic acid||butanedioic acid||HOOC-(CH2)2-COOH|
|Glutaric acid||pentanedioic acid||HOOC-(CH2)3-COOH|
|Adipic acid||hexanedioic acid||HOOC-(CH2)4-COOH|
|Pimelic acid||heptanedioic acid||HOOC-(CH2)5-COOH|
|Suberic acid||octanedioic acid||HOOC-(CH2)6-COOH|
|Azelaic acid||nonanedioic acid||HOOC-(CH2)7-COOH|
|Sebacic acid||decanedioic acid||HOOC-(CH2)8-COOH|
|Phthalic acid|| benzene-1,2-dicarboxylic acid|
|Isophthalic acid|| benzene-1,3-dicarboxylic acid|
|Terephthalic acid|| benzene-1,4-dicarboxylic acid|