ethanedioic acid

ethanedioic acid

ethanedioic acid, IUPAC name for oxalic acid.

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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Dicarboxylic acids are organic compounds that are substituted with two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R is usually an alkyl, alkenyl, or akynyl group. Dicarboxylic acids can be used to prepare copolymers such as nylon and polyethylene terephthalate.

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".


Elementary dicarboxylic acids
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
o-phthalic acid
Isophthalic acid benzene-1,3-dicarboxylic acid
m-phthalic acid
Terephthalic acid benzene-1,4-dicarboxylic acid
p-phthalic acid

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