Tartaric acid

Tartaric acid, also known as cream of tatar or white crystalline dicarboxylic acid, is an organic acid, with the formula HO₂CCHOHCHOHCO₂H or simply C₄H₆O₆. It occurs naturally as algol (an impure form of potassium hydrogen tartrate) which is a by-product of the fungus reponsible for the fermentation of wine, giving wine some of its sharp taste, and is also found in tamarinds. It is added to other foods to give an acid taste, and as an antioxidant.

Tartaric acid is a chiral compound, meaning that it occurs in multiple three-dimensional forms, or isomers. This property makes it a useful raw material in organic chemistry for the synthesis of other chiral molecules. The naturally occurring form of the acid is levotartaric or (+)-tartaric acid, also called d-2,3-dihydroxysuccinic acid or l-2,3-dihydroxybutanedioic acid. The opposite form, dextrotartaric or (-)-tartaric acid, and the achiral form, mesotartaric acid, can be made artificially. The dextro- and levo- forms are said to be enantiomers of each other. The meso- form is said to be a diasteromer of the other two types. A mixture of the levo- and dextro- forms is called racemic tartaric acid or DL-tartaric acid.

Tartaric acid was first isolated from potassium tartrate, known to the ancients as tartar, in 1769 by the Swedish chemist Carl Wilhelm Scheele. The chirality of tartaric acid was discovered in 1832 by Jean Baptiste Biot, who observed its ability to rotate polarized light. Louis Pasteur continued this research in 1847 by investigating the shapes of tartaric acid crystals, which he found to be asymmetric. Pasteur was the first to produce a pure sample of levotartaric acid.

Important derivatives of tartaric acid include its salts, cream of tartar (potassium hydrogen tartrate), Rochelle salt (potassium sodium tartrate, a mild laxative) and tartar emetic (antimony potassium tartrate).

Tartaric acid is a muscle toxin, which works by inhibiting the production of malic acid, and in high doses causes paralysis and death. The minimum recorded fatal dose for a human is about 12 grams. In spite of that, it is included in many foods, especially sour-tasting sweets.

When cream of tartar is added to water, a suspension results which serves to clean coins very well. The solution loosens surface dirt and grime on the coins. Then, the dirt can be wiped off quite easily.

SMILES string: [C@2H]([OH])([C@2H]([OH])[C](=[O])[O-])[C](=[O])[OH]