Tartaric acid, namely 2,3-dihydroxysuccinic acid, is a kind ofcarboxylic acid, chemical formula is CfourHsixOsix。It exists in many plants, such as grape and tamarind.It is also one of the main organic acids in wine.
As added in foodantioxidantIt can make food sour.The biggest use of tartaric acid is beverage additive, and it is also the raw material of pharmaceutical industry.
2. It is obtained from the reaction of glyoxal with hydrocyanic acid and acid hydrolysis.D-tartaric acid is found in many fruits or other parts of many plants. It exists in free state and also in combination with potassium, calcium and magnesium.
3. Tartaric acid is prepared and extracted from the coarse tartar sediment generated during the production of winePotassium hydrogen tartrate, and then converted toCalcium tartrateAfter salt, it is acidified with dilute sulfuric acid, or it can be obtained by oxidizing D-glucose with nitric acid.The preparation of DL tartaric acid is to azeotropize D-tartaric acid with NaOH aqueous solution.Put 49 gMaleic anhydride0.25 gTungstic acid130 g 30%hydrogen peroxideMix well with 50 ml of water, stir at 70 ℃ for 8 hours, and add flow for 1 hour.Cool the reaction solution and add 5mlconcentrated sulfuric acid, heat and boil for 1 hour.Cooling, precipitation and crystallization.Filter, wash the filter cake with water for three times, drain and dry to obtain 5g tartaric acid.
brief introduction
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history
Tartrate has historically played an important role in the establishment of organicStereochemistryIt worked.In 1769, Scheler obtained free colorless tartaric acid crystals from the fermentation broth of grape juice for the first time.Its variousStereoisomerandRacemateThey have different physical properties.Most of the things that exist in nature areDextral body, especially grape juice and other juice, so it is also calledFruit acid。For example, the racemate is obtained by controlled oxidation of butenedioic acid.The tartar produced in the above reaction process is treated with lime milk to generate calcium tartrate, and then acidified to obtainRacemate。In 1848, when French chemist Pasteur was engaged in the research on the crystallography of ammonium sodium tartrate, he saw an interesting phenomenon that had not been noticed by predecessors: the inactive ammonium sodium tartrate is a mixture composed of two different crystals, and their shapes are mirror images of each other, in fact, they are racemates.He used a magnifying glass and tweezers to carefully divide the mixture into small piles.One is dextral crystal, the other is left-handed crystal. They are like right gloves and left hand gloves.Both stacks of crystals are optically active when dissolved in water.He first discovered the molecularStereoisomerismAnd optical rotationEnantiomerismConcept, forOrganic stereochemistryAnd laid the foundation for its development.
Isomer
Tartaric acid has two identicalChiral carbon atom, there are three kinds of three-dimensional objects（Levorotator(L-tartaric acid), dextral (D-tartaric acid), racemate).L-tartaric acidAndD-tartaric acidbyEnantiomer。The naturally occurring tartaric acid is dextral.D-tartaric acid is widely distributed in higher plants in the form of free potassium salt, calcium salt and magnesium salt, especially in fruits and leaves.When making wine, a large amount of tartar (potassium hydroxide) will be deposited.In addition, it is also common in mold and lichen.A mixture of equal amounts of left-handed and right-handed bodies whose optical activity counteracts each other to form racemates.Racemic tartaric acid is also called gluconic acid.During the fermentation process of grape juice or other pulp juice, the acid potassium salt of dextral tartaric acid, which is insoluble in ethanol and water, is separated and deposited on the wall of the wine barrel, called tartar, from which tartaric acid is named.L-tartaric acid can be determined byRacemic resolutionIt is also found in the fruits and leaves of the Athyranthus in Mali.
Physical property data
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Melting point: 200-206 ℃
Boiling point: 399.3 ℃
Density: 1.886g/cmthree
Flash point: 210 ℃
Solubility: soluble in water and ethanol, slightly soluble in ether.
purpose
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Tartaric acid is often used to make medicinesMordantandtanning agentIt is also commonly used as a reagent for the resolution of racemic alkaline compounds.It is alsofood additivesThe acid taste of the product is better than that of malic acid and lactic acid.Several of its salts have important applications, such as in the laboratoryPotassium sodium tartratePreparationFehling's solution , used to identify aldehyde functional groups in organic molecular structure.Its potassium sodium salt is also called Rochelle salt. Its crystal polarizes under pressure, resulting in potential difference on the surface of both ends（Piezoelectric effect）And can be made into piezoelectric components for receivers and pickups of radio and wire broadcasting.Medical AdmiralPotassium antimony tartrate(commonly known as tartar spitting) for treatmentschistosomiasis。[2]
