Tartaric Acid
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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 re ...
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 approximately 8,0 ...
s but also in
tamarind Tamarind (''Tamarindus indica'') is a Legume, leguminous tree bearing edible fruit that is indigenous to tropical Africa and naturalized in Asia. The genus ''Tamarindus'' is monotypic taxon, monotypic, meaning that it contains only this spe ...
s,
banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...
s,
avocado The avocado, alligator pear or avocado pear (''Persea americana'') is an evergreen tree in the laurel family (Lauraceae). It is native to Americas, the Americas and was first domesticated in Mesoamerica more than 5,000 years ago. It was priz ...
s, and
citrus ''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. ''Citrus'' is nativ ...
. Its
salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of
fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...
. Potassium bitartrate is commonly mixed with
sodium bicarbonate Sodium bicarbonate ( IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda (or simply “bicarb” especially in the UK) is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cat ...
and is sold as
baking powder Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increas ...
used as a
leavening agent In cooking, a leavening agent () or raising agent, also called a leaven () or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An altern ...
in food preparation. The acid itself is added to foods as an
antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...
E334 and to impart its distinctive sour taste.
Naturally occurring A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical ...
tartaric acid is a useful raw material in
organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
. Tartaric acid, an alpha-hydroxy-
carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
, is diprotic 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 Pomerania, German-Swedish pharmaceutical chemist. Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified the elements molybd ...
. 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 , or , is a property of transverse waves which specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. One example of a polarize ...
.
Louis Pasteur Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist, pharmacist, and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation, and pasteurization, the la ...
continued this research in 1847 by investigating the shapes of sodium ammonium tartrate 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 (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...
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 In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
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 Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...
CRC Handbook of Chemistry and Physics, 49th edition. and
triclinic class=skin-invert-image, 180px, Triclinic (a ≠ b ≠ c ≠ a and α, β, γ, 90° pairwise different) In crystallography, the triclinic (or anorthic) crystal system is one of the seven crystal systems. A crystal system is described by three b ...
crystals (
space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...
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 (). This potassium salt is converted to
calcium tartrate Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...
() upon treatment with
calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime ( calcium oxide) is mixed with water. Annually, approxim ...
():J.-M. Kassaian "Tartaric acid" in Ullmann's Encyclopedia of Industrial Chemistry; VCH: Weinheim, Germany, 2002, 35, 671-678. : In practice, higher yields of calcium tartrate are obtained with the addition of
calcium sulfate Calcium sulfate (or calcium sulphate) is an inorganic salt with the chemical formula . It occurs in several hydrated forms; the anhydrous state (known as anhydrite) is a white crystalline solid often found in evaporite deposits. Its dihydrate ...
. Calcium tartrate is then converted to tartaric acid by treating the salt with aqueous sulfuric acid: :


Racemic tartaric acid

Racemic tartaric acid can be prepared in a multistep reaction from
maleic acid Maleic acid or ''cis''-butenedioic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Its chemical formula is HO2CCH=CHCO2H. Maleic acid is the ''cis'' Cis–trans isomerism, isomer of butenedioic 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 viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
using as a catalyst. : In the next step, the epoxide is hydrolyzed. :


''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. : ''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 In chemistry, iron(II) refers to the chemical element, element iron in its +2 oxidation number, oxidation state. The adjective ''ferrous'' or the prefix ''ferro-'' is often used to specify such compounds, as in ''ferrous chloride'' for iron(II ...
salt. :HO2CCH(OH)CH(OH)CO2H + H2O2 → HO2CC(OH)C(OH)CO2H + 2 H2O Dihydroxymaleic acid can then be oxidized to tartronic acid with nitric acid.


Derivatives

Important derivatives of tartaric acid include: * Sodium ammonium tartrate, the first material separated into its
enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...
s *cream of tartar ( potassium bitartrate), used in
cooking Cooking, also known as cookery or professionally as the culinary arts, is the art, science and craft of using heat to make food more palatable, digestible, nutritious, or Food safety, safe. Cooking techniques and ingredients vary widely, from ...
* Rochelle salt (potassium sodium tartrate), which has unusual piezoelectric properties * tartar emetic (antimony potassium tartrate), a resolving agent. Diisopropyl tartrate is used as a co-catalyst in asymmetric synthesis. Tartaric acid is a
muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
toxin A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...
, which works by inhibiting the production of
malic acid Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms ( ...
, 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 given substance. The value of LD50 for a substance is the dose re ...
(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 with 50% probability, so it may be safely included in many foods, especially sour-tasting sweets. As a
food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...
, tartaric acid is used as an
antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...
with
E number E numbers, short for Europe numbers, 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 object, usually round and flat, 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 to facilitate trade. They are most often issued by ...
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 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 barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden stave (wood), staves and bound by wooden or metal hoops. The word vat is often used for large containers ...
s 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 type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...
. In the mouth, tartaric acid provides some of the tartness in the wine, although citric and
malic acid Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms ( ...
s also play a role.


Tartaric acid in fruits

Grapes and tamarinds have the highest levels of tartaric acid concentration. Other fruits with tartaric acid are
banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...
s, avocados, prickly pear fruit,
apples An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...
,
cherries A cherry is the fruit of many plants of the genus ''Prunus'', and is a fleshy drupe (stone fruit). Commercial cherries are obtained from cultivars of several species, such as the sweet ''Prunus avium'' and the sour ''Prunus cerasus''. The name ...
, papayas,
peaches The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called nectarines. Peac ...
, pears,
pineapples The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many cent ...
,
strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid plant cultivated worldwide for its fruit. The genus ''Fragaria'', the strawberries, is in the rose family, Rosaceae. The fruit is appreciated f ...
, mangoes and citrus fruits. Trace amounts of tartaric acid have been found in cranberries and other
berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone fruit, stone or pit (fruit), pit although many wikt:pip#Etymology 2, pips or seeds may be p ...
. Tartaric acid is also present in the leaves and pods of
Pelargonium ''Pelargonium'' () is a genus of flowering plants that includes about 280 species of perennial plant, perennials, succulent plant, succulents, and shrubs, common name, commonly called geraniums, pelargoniums, or storksbills. ''Geranium'' is also ...
plants and
beans A bean is the seed of some plants in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying (a ''pulse''), but fresh beans are also sold. Dried beans are tradition ...
.


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 or fertiliser 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 liming materials or other non-nutrient soil amendments. Man ...
and for cleaning metal surfaces consisting of aluminium, copper, iron, and alloys of these metals, respectively.


Toxicity in dogs

While tartaric acid is well-tolerated by humans and lab animals, an April 2021 letter to the editor of '' JAVMA'' hypothesized that the tartaric acid in grapes could be the cause of grape and raisin toxicity in dogs. Two cases of after ingestion of
cream of tartar Potassium bitartrate, also known as potassium hydrogen tartrate, with formula K C4 H5 O6, is the potassium acid salt of tartaric acid (a carboxylic acid)—specifically, l-( + )-tartaric acid. Especially in cooking, it is also known as cream ...
caused a similar toxic reaction, with similar symptoms of
acute kidney injury Acute kidney injury (AKI), previously called acute renal failure (ARF), is a sudden decrease in renal function, kidney function that develops within seven days, as shown by an increase in serum creatinine or a decrease in urine output, or both. ...
and (in one case) similar histological findings in the kidneys at autopsy. A 2022 article expands on the letter with detailed reports of the 2 aforementioned cases of cream of tartar ingestion and 4 new cases of
tamarind Tamarind (''Tamarindus indica'') is a Legume, leguminous tree bearing edible fruit that is indigenous to tropical Africa and naturalized in Asia. The genus ''Tamarindus'' is monotypic taxon, monotypic, meaning that it contains only this spe ...
ingestion. Again, clinical findings were similar. Tamarind is known to contain 8%–18% tartaric acid, much more than the up to 2% (typically 0.35%–1.1%) found in grapes. The authors believe that the assignment of tartaric acid as the culprit also explains the relative lack of incidents from dogs consuming commercial grape juice, jam, and wine, as these go through a process to remove tartrates. A 2023 study have observed tartaric acid toxicity in kidney cells of dogs, but not in human kidney cells. A 2024 review identified a relationship between grape ingestion and illness, though the specific type or quantity of grapes that cause toxicity remains unclear. Grape ingestion commonly leads to gastrointestinal and/or renal issues, with treatment depending on the symptoms; outcomes can vary.


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