Tartaric Acid Formula: What makes tamarind sour? It’s tartaric acid. The IUPAC name of tartaric acid is 2,3-dihydroxybutanedioic acid. It occurs naturally in many plants such as grapes and tamarinds and is one of the main acids found in wine. It is used as an antioxidant. Salts of tartaric acid are known as tartrates. It is a dihydroxy derivative of dicarboxylic acid.

Tartaric Acid Formula: Overview 

Tartaric acid is a white crystalline organic acid and is an important dicarboxylic acid with the molecular formula \({{\rm{C}}_{\rm{4}}}{{\rm{H}}_{\rm{6}}}{{\rm{O}}_{\rm{6}}}\) The chemical formula of tartaric acid can be written as \({\rm{HOOC – CH(OH) – CH(OH) – COOH}}\) or \({\left( {{\rm{CH}}({\rm{OH}}){\rm{ – COOH}}} \right)_2}\).

Molar Mass of Tartaric Acid

The molar mass of Tartaric Acid, \({\rm{HOOC}}\,{\rm{ – }}\,{\rm{CH(OH)}}\,{\rm{ – }}\,{\rm{CH(OH) – COOH}}\) is:
\({\rm{4}}\left( {{\rm{The}}\,{\rm{atomic}}\,{\rm{mass}}\,{\rm{of}}\,{\rm{carbon}}} \right){\rm{ + 6}}{\mkern 1mu} \left( {{\rm{The}}\,{\rm{atomic}}\,{\rm{mass}}\,{\rm{of}}{\mkern 1mu} {\rm{hydrogen}}} \right){\rm{ + 6}}\left( {{\rm{Atomic}}\,{\rm{mass}}{\mkern 1mu} \,{\rm{of}}{\mkern 1mu} \,{\rm{Oxygen}}} \right){\rm{ = 4}}\left( {{\rm{12}}{\rm{.01}}\,{\rm{u}}} \right){\rm{ + 6}}\left( {{\rm{1}}{\rm{.007}}\,{\rm{u}}} \right){\rm{ + 6}}\left( {15.99\,{\rm{u}}} \right) = 150.09\,{\rm{g}}\,{\rm{mo}}{{\rm{l}}^{ – 1}}\)

Hence, molar mass of Tartaric acid is \({\rm{150}}{\rm{.09}}\,{\rm{g}}\,{\rm{mo}}{{\rm{l}}^{ – 1}}\)

Structure of Tartaric Acid

Tartaric acid is dihydroxy with two \({\rm{OH}}\) groups and a dicarboxylic acid with two \({\rm{COOH}}\) groups. The simple structural formula of tartaric acid is shown below:

Stereochemistry

Tartaric acid is a chiral molecule meaning that it has molecules that are non-superimposable on its mirror images. Hence, it exists as three stereoisomers (having the same composition but different orientations in space): Dextrotartaric acid or D-tartaric acid, levotartaric acid or L-tartaric acid meso-tartaric acid, which have slightly different structures as shown below. Racemic tartaric acid is an equal mixture of D- and L-tartaric acid. The levotartaric acid is the mirror-image (enantiomeric) form of D-tartaric acid, and the meso-tartaric acid is the diastereomer of both of them.

levotartaric acid \(({\rm{D – }}( + ){\rm{ – tartaric}}{\mkern 1mu} {\mkern 1mu} {\rm{acid}})\)	dextrotartaric acid \({\rm{(L – ( + ) – tartaric}}\,\,{\rm{acid)}}\)	mesotartaric acid
	\({\rm{DL}}\) (racemic acid)(when in \({\rm{1}}\,\,{\rm{:}}\,\,{\rm{1}}\)

The dextro and levo prefixes are not related to the \({\rm{D/L}}\) configuration (derived from the reference \({\rm{D – }}\,{\rm{or}}\,{\rm{L – }}\)glyceraldehyde). These are related to the orientation of the optical rotation, \({\rm{( + )}}\,{\rm{ =  }}\) dextrorotatory, \({\rm{( – )}}\,{\rm{ =  }}\) levorotatory. Sometimes, instead of capital letters, small italic \({\rm{d, l}}\) is used. They are abbreviations of dextro- and levo-.

Preparation: The L(-)-tartaric acid isomer is the most common form and thus is produced in the largest quantities. It is prepared by reacting calcium tartrate with aqueous sulfuric acid to give L(-)-tartaric acid:

\({\rm{Ca}}\left( {{{\rm{O}}_{\rm{2}}}{\rm{CCH}}\left( {{\rm{OH}}} \right){\rm{CH}}\left( {{\rm{OH}}} \right){\rm{C}}{{\rm{O}}_{\rm{2}}}} \right){\rm{ + }}{{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}} \to {\rm{H}}{{\rm{O}}_{\rm{2}}}{\rm{CCH}}\left( {{\rm{OH}}} \right){\rm{CH}}\left( {{\rm{OH}}} \right){\rm{C}}{{\rm{O}}_{\rm{2}}}{\rm{H + CaS}}{{\rm{O}}_{\rm{4}}}\)

Physical Properties of Tartaric Acid

1. Tartaric acid is a colourless, crystalline solid. 
2. It has a density of \(1.79\,{\rm{g}}/{\rm{mL}}\) and melting point range \({\rm{171}}\,^\circ {\rm{C}}\) to \({\rm{174}}\,^\circ {\rm{C}}\).
3. All forms of tartaric acid are readily soluble in water.

Chemical Properties of Tartaric Acid 

1. Tartaric acid is an alpha-hydroxy diprotic dicarboxylic acid.
2. It can form salts with bases. Some of the important salts of tartaric acid are cream of tartar (potassium hydrogen tartrate) and Rochelle salt (potassium sodium tartrate). 
3. Tartaric acid is an optically active compound and was one of the first chemicals to be studied regarding stereoisomerism.

Uses of Tartaric Acid

1. Tartaric acid has a wide range of applications in the food industry due to its sour taste and antioxidant properties.
2. It is widely used in sour candies, carbonated drinks, effervescent tablets, gelatins, jellies and baking powders.
3. Its industrial uses include photographic printing and development, polishing metals, wool dyeing, etc.
4. The tartrate salts are used in silvering mirrors, cleaning brass, dyeing mordant, and an insecticide.
5. Rochelle’s salt is used in processed cheese.
6. Creme of tartar is used in baking powders, cleaning brass, electrolytic tinning of iron and steel, and coating other metals with gold and silver.
7. Tartar emetic (antimony potassium tartrate) is used as an insecticide and dyeing mordant.

Health Effects/Safety Hazards

Tartaric acid is safe for human consumption in low doses and is used in food products. However, it is a muscle toxins in large doses, which can cause paralysis and death when swallowed.

Summary

Tartaric acid plays an important role chemically. It lowers the pH of fermentation and acts as a preservative after fermentation. In this article, we learnt the formula, structure, stereochemistry and properties of tartaric acid. We also learnt about some of its important salts, such as Rochelle’s salt and crème of tartar. Rochelle salt, is a double salt of tartaric acid. It is extensively used in the process of silvering mirrors and is an important ingredient of Fehling’s solution (reagent for reducing sugars). Another important salt of tartaric acid used extensively for cooking purposes is the cream of tartar. It is processed from the potassium acid salt of tartaric acid. The resulting acid is not a crème but a powder that can be used in baking or as a cleaning solution. 

Frequently Asked Questions (FAQs) on Tartaric Acid Formula

Q.1. What is the chemical name of tartaric acid?
Ans: The chemical name of tartaric acid is \({\rm{2 – 3 – }}\)dihydroxybutanedioic acid.

Q.2. Is tartaric acid a weak acid?
Ans: Tartaric acid is a weak acid that dissociates, in solution, into bitartrate and tartrate ions.

Q.3. Is tartaric acid the same as cream of tartar?
Ans: Tartaric acid and cream of tartar are not quite the same things. The cream of tartar is made from tartaric acid by combining it with potassium hydroxide. This partially neutralizes the tartaric acid, so the cream of tartar is less acidic than tartaric acid.

Q.4. What is the cream of tartar? 
Ans: Cream of tartar is not creamy. It’s a dry, powdery, acidic byproduct of grapes fermentation into wine. Its scientific name is potassium hydrogen tartrate.

Q.5. What are the uses of tartaric acid?
Ans: Tartaric acid is often used as an antioxidant. It is widely used in gelatin desserts, jams, jellies, and sour confectionaries. The acidic monopotassium or ‘cream of tartar’ is used in baking powders and leavening systems.

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