chemistry

Tartaric acid

Tartaric acid is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tartaric acid rather than just read about it. In short: Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes but also in tamarinds, bananas, avocados, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of fermentation.

Key takeaways

Tartaric acid belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tartaric acid to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tartaric acid from memory before moving on to harder problems.

Reference excerpt

Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes but also in tamarinds, bananas, avocados, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of fermentation. Potassium bitartrate 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 E334 and to impart its distinctive sour taste. Naturally occurring tartaric acid is a useful raw material in organic synthesis. Tartaric acid, an alpha-hydroxy-carboxylic acid, 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– its crude crystalline form as found off top of wine barrels were called tartarum (rendered tartre by Chaucer) or "wine stone". However, chemical extraction and purification was developed in 1769 by the Swedish chemist Carl Wilhelm Scheele. 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 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 and the meso isomer. The dextro and levo prefixes are archaic terms. Modern textbooks refer to the natural form as (2R,3R)-tartaric acid (L-(+)-tartaric acid), and its enantiomer as (2S,3S)-tartaric acid (D-(−)-tartaric acid). The meso diastereomer is referred to as (2R,3S)-tartaric acid or (2S,3R)-tartaric acid.

Dextro and levo form monoclinic sphenoidal crystals and orthorhombic crystals. Racemic tartaric acid (racemic acid) forms monoclinic and triclinic crystals (space group P1). 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 (KHC4H4O6). This potassium salt is converted to calcium tartrate (CaC4H4O6) upon treatment with calcium hydroxide (Ca(OH)2):

KH(C4H4O6) + Ca(OH)2 → Ca(C4H4O6) + KOH + H2O In practice, higher yields of calcium tartrate are obtained with the addition of calcium sulfate. 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 using potassium tungstate as a catalyst.

HO2CCH=CHCO2H + H2O2 → HO2C(CHCH)(O)CO2H + H2O In the next step, the epoxide is hydrolyzed.

HO2C(CHCH)(O)CO2H + H2O → HO2CCH(OH)CH(OH)CO2H

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:

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, dihydroxymalonic 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 with nitric acid.

Derivatives

Important derivatives of tartaric acid include:

Sodium ammonium tartrate, the first material separated into its enantiomers cream of tartar (potassium bitartrate), used in cooking 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 toxin, which works by inhibiting the production of malic acid, and in high doses causes paralysis and death. The median lethal dose (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 500 g (18 oz) to kill a person weighing 70 kg (150 lb) with 50% probability, so it may be safely included in many foods, especially sour-tasting sweets. As a food additive, tartaric acid is used as an antioxidant with E number E334; tartrates are other additives serving as antioxidants or emulsifiers. When cream of tartar is added to water, a suspension results which serves to clean copper coins 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

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Tartaric acid

Start with the simplest possible case. Write down what Tartaric acid claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tartaric acid before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tartaric acid ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tartaric acid

In research: Tartaric acid appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tartaric acid in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tartaric acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acids in wine, Alpha hydroxycarboxylic acids, Chirality, so understanding it makes those chapters shorter.
In everyday life: Look for Tartaric acid outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Tartaric acid” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Tartaric acid in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tartaric acid means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tartaric acid out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tartaric acid in simple terms?

Why does Tartaric acid matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tartaric acid?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tartaric acid.