Tartaric acid is a white, crystalline
organic acid
An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are ...
that occurs naturally in many fruits, most notably in
grape
A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters.
The cultivation of grapes began perhaps 8,000 years a ...
s, but also in
bananas,
tamarind
Tamarind (''Tamarindus indica'') is a leguminous tree bearing edible fruit that is probably indigenous to tropical Africa. The genus ''Tamarindus'' is monotypic, meaning that it contains only this species. It belongs to the family Fabacea ...
s, and
citrus
''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...
.
Its
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
,
potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of
fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...
. It is commonly mixed with
sodium bicarbonate and is sold as
baking powder used as a
leavening agent in food preparation. The acid itself is added to foods as an
antioxidant
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubrica ...
E334 and to impart its distinctive sour taste.
Naturally occurring tartaric acid is a useful raw material in
organic
Organic may refer to:
* Organic, of or relating to an organism, a living entity
* Organic, of or relating to an anatomical organ
Chemistry
* Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...
chemical synthesis
As a topic of chemistry, chemical synthesis (or combination) is the artificial execution of chemical reactions to obtain one or several products. This occurs by physical and chemical manipulations usually involving one or more reactions. In mod ...
. Tartaric acid is an alpha-hydroxy-
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxyli ...
, is
diprotic
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
and
aldaric in acid characteristics, and is a dihydroxyl derivative of
succinic acid.
History
Tartaric acid has been known to
winemakers for centuries. However, the chemical process for extraction was developed in 1769 by the
Swedish chemist
Carl Wilhelm Scheele
Carl Wilhelm Scheele (, ; 9 December 1742 – 21 May 1786) was a Swedish German pharmaceutical chemist.
Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hydr ...
.
Tartaric acid played an important role in the discovery of
chemical chirality. This property of tartaric acid was first observed 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
sodium ammonium tartrate
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isot ...
crystals, which he found to be chiral. By manually sorting the differently shaped crystals, Pasteur was the first to produce a pure sample of levotartaric acid.
Stereochemistry
Naturally occurring form of the acid is dextro tartaric acid or
L-(+)-tartaric acid (obsolete name
''d''-tartaric acid). Because it is available naturally, it is cheaper than its
enantiomer
In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical anti ...
and the
meso isomer. The ''dextro'' and ''levo'' prefixes are archaic terms. Modern textbooks refer to the natural form as (2''R'',3''R'')-tartaric acid (
L-(+)-tartaric acid), and its enantiomer as (2''S'',3''S'')-tartaric acid (D-(-)-tartaric acid). The ''meso'' diastereomer is referred to as (2''R'',3''S'')-tartaric acid or (2''S'',3''R'')-tartaric acid.
*Dextro and levo form
monoclinic sphenoidal crystals and
orthorhombic crystals.
*Racemic tartaric acid forms
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...
[CRC Handbook of Chemistry and Physics, 49th edition.] and
triclinic crystals (
space group P).
*Anhydrous meso tartaric acid form two anhydrous
polymorphs: triclinic and orthorhombic.
*Monohydrated meso tartaric acid crystallizes as monoclinic and triclinic polymorphys depending on the temperature at which crystallization from aqueous solution occurs.
Tartaric acid in
Fehling's solution binds to copper(II) ions, preventing the formation of insoluble hydroxide salts.
Production
L-(+)-Tartaric acid
The
L-(+)-tartaric acid isomer of tartaric acid is industrially produced in the largest amounts. It is obtained from
lees, a solid byproduct of fermentations. The former byproducts mostly consist of potassium bitartrate (KHC
4H
4O
6). This potassium salt is converted to calcium tartrate (CaC
4H
4O
6) upon treatment with
calcium hydroxide "milk of lime" (Ca(OH)
2):
[J.-M. Kassaian "Tartaric acid" in Ullmann's Encyclopedia of Industrial Chemistry; VCH: Weinheim, Germany, 2002, 35, 671-678. ]
:
KH(C4H4O6) + Ca(OH)2 -> Ca(C4H4O6) + KOH + H2O
In practice, higher yields of calcium tartrate are obtained with the addition of
calcium chloride. Calcium tartrate is then converted to tartaric acid by treating the salt with aqueous sulfuric acid:
:
Ca(C4H4O6) + H2SO4 -> H2(C4H4O6) + CaSO4
Racemic tartaric acid
Racemic tartaric acid can be prepared in a multistep reaction from
maleic acid. In the first step, the maleic acid is
epoxidized by
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...
using
potassium tungstate as a catalyst.
[
:HO2CC2H2CO2H + H2O2 → OC2H2(CO2H) 2
In the next step, the epoxide is hydrolyzed.
:OC2H2(CO2H)2 + H2O → (HOCH)2(CO2H)2
]
''meso''-Tartaric acid
A mixture of racemic acid and ''meso''-tartaric acid is formed when ''dextro''-Tartaric acid is heated in water at 165 °C for about 2 days. ''meso''-Tartaric acid can also be prepared from dibromosuccinic acid using silver hydroxide:[Augustus Price West. Experimental Organic Chemistry. World Book Company: New York, 1920, 232-237.]
:HO2CCHBrCHBrCO2H + 2 AgOH → HO2CCH(OH)CH(OH)CO2H + 2 AgBr
''meso''-Tartaric acid can be separated from residual racemic acid by crystallization, the racemate being less soluble.
Reactivity
L-(+)-tartaric acid, can participate in several reactions. As shown the reaction scheme below, dihydroxymaleic acid is produced upon treatment of L-(+)-tartaric acid with hydrogen peroxide in the presence of a ferrous salt.
:HO2CCH(OH)CH(OH)CO2H + H2O2 → HO2CC(OH)C(OH)CO2H + 2 H2O
Dihydroxymaleic acid can then be oxidized to tartronic acid
Tartronic acid or 2-hydroxymalonic acid is an organic compound with the structural formula of HOHC(CO2H)2. This dicarboxylic acid is related to malonic acid.
Its derivative, 2-methyltartronic acid, is isomalic acid.
Uses
Tartronic acid is best ...
with nitric acid.
Derivatives
Important derivatives of tartaric acid include its salts, cream of tartar ( potassium bitartrate), Rochelle salt (potassium sodium tartrate, a mild laxative), and tartar emetic (antimony potassium tartrate). Diisopropyl tartrate
Diisopropyl tartrate (DIPT) is a diester of tartaric acid. It has a two chiral carbon atoms giving rise to three stereoisomeric variants. It is commonly used in asymmetric synthesis as a catalyst and as chiral building block for pharmaceuticals ...
is used as a co-catalyst in asymmetric synthesis.
Tartaric acid is a muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...
toxin
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...
, which works by inhibiting the production of malic acid, and in high doses causes paralysis and death. The median lethal dose
In toxicology, the median lethal dose, LD50 (abbreviation for " lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is ...
(LD50) is about 7.5 grams/kg for a human, 5.3 grams/kg for rabbits, and 4.4 grams/kg for mice. Given this figure, it would take over to kill a person weighing , so it may be safely included in many foods, especially sour-tasting sweets. As a food additive, tartaric acid is used as an antioxidant
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubrica ...
with E number
E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...
E334; tartrates are other additives serving as antioxidants or emulsifiers
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although ...
.
When cream of tartar is added to water, a suspension results which serves to clean copper coin
A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order ...
s very well, as the tartrate solution can dissolve the layer of copper(II) oxide present on the surface of the coin. The resulting copper(II)-tartrate complex is easily soluble in water.
Tartaric acid in wine
Tartaric acid may be most immediately recognizable to wine drinkers as the source of "wine diamonds", the small potassium bitartrate crystals that sometimes form spontaneously on the cork
Cork or CORK may refer to:
Materials
* Cork (material), an impermeable buoyant plant product
** Cork (plug), a cylindrical or conical object used to seal a container
***Wine cork
Places Ireland
* Cork (city)
** Metropolitan Cork, also known as G ...
or bottom of the bottle. These "tartrates" are harmless, despite sometimes being mistaken for broken glass, and are prevented in many wines through cold stabilization (which is not always preferred since it can change the wine's profile). The tartrates remaining on the inside of aging barrels were at one time a major industrial source of potassium bitartrate.
Tartaric acid plays an important role chemically, lowering the pH of fermenting "must" to a level where many undesirable spoilage bacteria cannot live, and acting as a preservative after fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...
. In the mouth, tartaric acid provides some of the tartness in the wine, although citric and malic acids also play a role.
Tartaric acid in citrus
Results from a study showed that in citrus, fruits produced in organic farming contain higher levels of tartaric acid than fruits produced in conventional agriculture.
Applications
Tartaric acid and its derivatives have a plethora of uses in the field of pharmaceuticals. For example, it has been used in the production of effervescent salts, in combination with citric acid, to improve the taste of oral medications. The potassium antimonyl derivative of the acid known as tartar emetic is included, in small doses, in cough syrup as an expectorant.
Tartaric acid also has several applications for industrial use. The acid has been observed to chelate metal ions such as calcium and magnesium. Therefore, the acid has served in the farming and metal industries as a chelating agent for complexing micronutrients in soil fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
and for cleaning metal surfaces consisting of aluminium, copper, iron, and alloys of these metals, respectively.[
]
Toxicity in canines
While tartaric acid is well tolerated by humans and lab animals, an April 2021 letter to the editor of ''JAVMA
The American Veterinary Medical Association (AVMA), founded in 1863, is a not-for-profit association representing more than 99,500 veterinarians in the US.
The AVMA provides information resources, continuing education opportunities, publicatio ...
'' hypothesized that the tartaric acid in grapes could be the cause of grape and raisin toxicity in dogs.
References
External links
PDB file for MSE
{{DEFAULTSORT:Tartaric Acid
Crystals in space group 14
Chirality
Racemic mixtures
Food antioxidants
Food acidity regulators
Acids in wine
Alpha hydroxy acids
Dicarboxylic acids
Vicinal diols
E-number additives