tartaric acid

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Tartaric Acid

The chemistry of tartaric acid

Uses of tartaric acid

Tartaric acid is an organic (carbon based) compound of the chemical formula C4H6O6, and has the official name 2,3-dihydroxybutanedioic acid. In this name, the 2,3-dihydroxy refers to the two OH groups on the second and third carbon atoms, and the butane portion of the name refers to a four-carbon molecule. The dioic acid portion communicates the existence of two organic acid (COOH) groups on the molecule. Tartaric acid is found throughout nature, especially in

many fruits and in wine. In addition to existing freely, it is also found as a salt (salts are the products of acids and bases), the most common of which are calcium tartrate, potassium tartrate, and sodium tartrate.

Tartaric acid is used making silver mirrors, in the manufacturing of soft drinks, to provide tartness to foods, in tanning leather and in making blueprints. Tartaric acid is used in cream of tartar (for cooking) and as an emetic (a substance used to induce vomiting). It readily dissolves in water and is used in making blueprints. Tartaric acid is a molecule that demonstrates properties of optical activity, where a molecule can cause the rotation of plane-polarized light. Tartaric acid exists in four forms (isomers are molecular rearrangements of the same atoms), each of which affects plane-polarized light differently.

The chemistry of tartaric acid

Tartaric acid is a white solid, possessing two alcohol groups and two acid groups. The second and third carbons of the molecule are asymmetrical (these are called chiral centers). The naturally occurring form of tartaric acid is the L-isomer, which rotates light to the left. The D-form of the acid, which rotates plane-polarized light to the right (the D refers to dextro, or right hand direction) is far less common in nature and has almost no practical uses. In general, where biological molecules have optical isomers, only one of the isomers or forms will be active biologically. The other will be unaffected by the enzymes in living cells. The meso form of the molecule does not affect polarized light. Figure 1 shows the D, L, and meso forms of tartaric acid. The fourth formthe DL mixtureis not a single molecule, but a mixture of equal amounts of D and L isomers. It does not rotate polarized light either (like the meso form) because the rotation of

KEY TERMS

Chiral center A carbon atom with four different atoms or groups of atoms attached to it (sometimes called an asymmetrical carbon). Chiral centers can cause the rotation of polarized light.

Emetic A substance used to induce vomiting, usually to remove a poison from the body.

Isomers Two molecules in which the number of atoms and the types of atoms are identical, but their arrangement in space is different, resulting in different chemical and physical properties. Isomers based on chiral centers (such as tartaric acid) are sometimes called stereoisomers.

Polarized light Light in which the waves vibrate in only one plane, as opposed to the normal vibration of light in all planes.

Salts Compounds that are the products of the reaction of acids and bases. Sodium tartrate is the product of the reaction between sodium hydroxide and tartaric acid.

light by the D and L forms is equal in amount but opposite in direction. It is possible to separate the DL mixture into the two isomers, each of which does rotate light. In the 1840s Louis Pasteur determined that each of the two isomers of tartaric acid rotated light in opposite directions, and the meso form was inactive in this respect. He also separated by hand crystals of the racemic mixture to show that it was made of equal amounts of the D and L forms, making it different than the meso form of tartaric acid.

Uses of tartaric acid

Tartaric acid is found in cream of tartar, which is used in cooking candies and frostings for cakes. Tartaric acid is also found in baking powder, where it serves as the source of acid that reacts with sodium bicarbonate (baking soda). This reaction produces carbon dioxide gas, and lets products rise, but does so without any yeasty taste, that can result from using active yeast cultures as a source of the carbon dioxide gas. Tartaric acid is used in silvering mirrors, tanning leather, and in Rochelle Salt, which is sometimes used as a laxative. Blue prints are made with ferric tartarte as the source of the blue ink. In medical analysis, tartaric acid is used to make solutions for the determination of glucose. Common esters of tartaric acid are diethyl tartrate and dibutyl tartrate, which are made by reacting tartaric acid with ethanol and butanol. In this reaction, the H of the COOH acid group is replaced with a CH3CH2 (ethyl) group or a butyl group (CH3CH2CH2CH2<-b1.0001>-). These esters are used in manufacturing lacquer and in dyeing textiles.

Louis Gotlib

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Tartaric acid

Tartaric acid is an organic (carbon based) compound of the chemical formula C4H6O6, and has the official name 2,3-dihydroxybutanedioic acid. In this name, the 2,3-dihydroxy refers to the two OH groups on the second and third carbon atoms , and the butane portion of the name refers to a four-carbon molecule . The dioic acid portion communicates the existence of two organic acid (COOH) groups on the molecule. Tartaric acid is found throughout nature, especially in many fruits and in wine. In addition to existing freely, it is also found as a salt (salts are the products of acids and bases ), the most common of which are calcium tartrate, potassium tartrate, and sodium tartrate.

Tartaric acid is used making silver mirrors , in the manufacturing of soft drinks, to provide tartness to foods, in tanning leather and in making blueprints. Tartaric acid is used in cream of tartar (for cooking) and as an emetic (a substance used to induce vomiting). It readily dissolves in water and is used in making blueprints. Tartaric acid is a molecule that demonstrates properties of optical activity, where a molecule can cause the rotation of plane-polarized light . Tartaric acid exists in four forms (isomers are molecular rearrangements of the same atoms), each of which affects plane-polarized light differently.


The chemistry of tartaric acid

Tartaric acid is a white solid, possessing two alcohol groups and two acid groups. The second and third carbons of the molecule are asymmetrical (these are called chiral centers). The naturally occurring form of tartaric acid is the L-isomer, which rotates light to the left. The D-form of the acid, which rotates plane-polarized light to the right (the D refers to dextro, or right hand direction) is far less common in nature and has almost no practical uses. In general, where biological molecules have optical isomers, only one of the isomers or forms will be active biologically. The other will be unaffected by the enzymes in living cells. The meso form of the molecule does not affect polarized light. Figure 1 shows the D, L, and meso forms of tartaric acid. The fourth form—the DL mixture—is not a single molecule, but a mixture of equal amounts of D and L isomers. It does not rotate polarized light either (like the meso form) because the rotation of light by the D and L forms is equal in amount but opposite in direction. It is possible to separate the DL mixture into the two isomers, each of which does rotate light. In the 1840s Louis Pasteur determined that each of the two isomers of tartaric acid rotated light in opposite directions, and the meso form was inactive in this respect. He also separated by hand crystals of the racemic mixture to show that it was made of equal amounts of the D and L forms, making it different than the meso form of tartaric acid.


Uses of tartaric acid

Tartaric acid is found in cream of tartar, which is used in cooking candies and frostings for cakes. Tartaric acid is also found in baking powder, where it serves as the source of acid that reacts with sodium bicarbonate (baking soda). This reaction produces carbon dioxide gas, and lets products "rise," but does so without any "yeasty"taste , that can result from using active yeast cultures as a source of the carbon dioxide gas. Tartaric acid is used in silvering mirrors, tanning leather, and in Rochelle Salt, which is sometimes used as a laxative. Blue prints are made with ferric tartarte as the source of the blue ink. In medical analysis, tartaric acid is used to make solutions for the determination of glucose. Common esters of tartaric acid are diethyl tartrate and dibutyl tartrate, which are made by reacting tartaric acid with ethanol and butanol. In this reaction, the H of the COOH acid group is replaced with a CH3CH2 (ethyl) group or a butyl group (CH3 CH2CH2CH2-). These esters are used in manufacturing lacquer and in dyeing textiles .


Resources

periodicals

Hunter, Beatrice. "Technological vs. Biological Needs." Consumer Research Magazine (August 1988): 8.


Louis Gotlib

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chiral center

—A carbon atom with four different atoms or groups of atoms attached to it (sometimes called an asymmetrical carbon). Chiral centers can cause the rotation of polarized light.

Emetic

—A substance used to induce vomiting, usually to remove a poison from the body.

Isomers

—Two molecules in which the number of atoms and the types of atoms are identical, but their arrangement in space is different, resulting in different chemical and physical properties. Isomers based on chiral centers (such as tartaric acid) are sometimes called stereoisomers.

Polarized light

—Light in which the waves vibrate in only one plane, as opposed to the normal vibration of light in all planes.

Salts

—Compounds that are the products of the reaction of acids and bases. Sodium tartrate is the product of the reaction between sodium hydroxide and tartaric acid.

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tartaric acid A dibasic acid, chemically dihydroxysuccinic acid. Occurs in fruits, the chief source being grapes; used in preparing lemonade, added to jams when the fruit is not sufficiently acidic (citric acid also used) and in baking powder. Rochelle salt is potassium sodium tartrate. See also cream of tartar.

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tar·tar·ic ac·id • n. Chem. a crystalline organic acid, COOH(CHOH)2COOH, that is present esp. in unripe grapes and is used in baking powders and as a food additive.

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