Copper (II) tartrate

Structural formula
anhydrous copper (II) tartrate of L-tartaric acid
General
Surname	Copper (II) tartrate
other names	Copper (II) bis (2,3-dihydroxybutanedioate) ( IUPAC ) Tartaric acid copper (II) salt
Molecular formula	C 4 H 4 CuO 6
Brief description	green to blue solid (hydrate)
External identifiers / databases
CAS number 815-82-7 ( L -artrate, anhydrous) 946843-80-7 ( L -artrate, unspec. Hydrate) 5893-71-0 ( L -artrate, trihydrate) EC number 212-425-0 ECHA InfoCard 100.011.295 PubChem 13155 Wikidata Q18212139
properties
Molar mass	211.62 g mol −1 (anhydrous)
Physical state	firmly
solubility	sparingly soluble in water
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

When copper (II) tartrate which is referred to copper (II) salt of tartaric acid . As a result of the stereochemistry of tartaric acid, there are three stereoisomers. These are the enantiomer pair copper (II) - L -tartrate and copper (II) - D -tartrate, as well as the copper (II) - meso -tartrate. They are bluish crystals or powders that are present as complex compounds . The salts have a 1: 1 stoichiometry with regard to the copper and tartrate ions with CuC ₄ H ₄ O ₆ . Copper-tartrate complexes with a stoichiometry of 1: 2 to 1: 6 still exist in aqueous solution. The detection reagent of the Fehling's sample also contains a copper tartrate complex.

history

Johann Rudolph Glauber discovered copper (II) tartrate and described it for the first time.

presentation

The production of copper (II) tartrates is carried out by converting copper (II) salts with the corresponding tartaric acid . Copper (II) L- tartrate can be obtained by precipitation from aqueous copper (II) acetate solution with L-tartaric acid. It can also be produced from copper (II) chloride solutions. Copper (II) D tartrate and copper (II) meso tartrate were obtained by slow evaporative crystallization from solutions of basic copper (II) carbonate and D or meso tartaric acid. All salts are obtained as trihydrates. An anhydrous salt can be obtained from disodium tartrate and copper (II) chloride solutions. The precipitate obtained by heating on a water bath is stored in the desiccator over dry calcium chloride . It is industrially obtained in small quantities from tartar (potassium hydrogen tartrate) with caustic soda and copper sulfate.

properties

Physical Properties

All copper (II) tartrates are present as trihydrates at room temperature. Single-crystal examinations revealed an orthorhombic crystal lattice for copper (II) meso-tartrate trihydrate and a monoclinic crystal lattice for copper (II) -D-tartrate trihydrate. An orthorhombic crystal lattice was found for the copper (II) -L-tartrate trihydrate. Since the L- and D-tartrate represent a pair of enantiomers, an orthorhombic and a monoclinic, polymorphic crystal structure should be possible for both stereoisomers. By means of X-ray diffraction single crystal investigations, a polymer complex structure [Cu ₂ (C ₄ H ₄ O ₆ ) ₂ (H ₂ O) ₂ ] · 4H ₂ O} _{∞ could be} determined, in which each copper (II) ion is octahedral with six oxygen atoms is coordinated by a water molecule and three tartrations. The two tartrations in the [Cu ₂ (C ₄ H ₄ O ₆ ) ₂ (H ₂ O) ₂ ] complex structure have a different coordination to the copper ions, one is bound with five tartrate oxygen atoms, the other with six tartrate oxygen atoms.

The copper (II) tartrates are readily soluble in water and result in clearly blue colored aqueous solutions.

Copper (II) tartrate complexes with different stoichiometry can be present in aqueous solutions . The copper ion is surrounded by one to six tartrate ions, each of which is oriented towards the copper with the carboxy group .

Chemical properties

Copper (II) tartrate reacts with some organic reagents as an oxidizing agent . The copper (II) ion is reduced to the copper (I) ion. In the presence of hydroxide ions , for example, aldehydes can be selectively oxidized. The formation of a complex with tartrate prevents the precipitation of copper (II) hydroxide , which would interfere with the reaction. Red copper (I) oxide is formed from the copper (I) ion :

${\displaystyle \mathrm {2\ Cu^{2+}+R-CHO+5\ OH^{-}} }$ ${\displaystyle \mathrm {\longrightarrow Cu_{2}O+R-COO^{-}+3\ H_{2}O} }$

Reaction with aldehydes

When heated in the thermobalance , a decrease in mass is observed from 200 ° C. The residue consists of copper (I) oxide.

use

Copper (II) tartrate is used in combination with sodium hydroxide solution in organic chemistry to detect aldehydes or reducing sugars ( Fehling's test via the formation of alkaline copper tartrate solution ) or to absorb formaldehyde in gas washing bottles . This is oxidized to formic acid and is therefore no longer toxic:

${\displaystyle \mathrm {2\ Cu^{2+}+H_{2}CO+5\ OH^{-}\longrightarrow Cu_{2}O+HCOO^{-}+3\ H_{2}O} }$

Oxidation of formaldehyde

Detection of D-glucose via oxidation

Copper (II) tartrate is a mild oxidizing agent similar to silver (I) diammine . Thermolysis of mixed crystals of copper (II) tartrate and zinc (II) tartrate results in copper / zinc oxide catalysts relevant for methanol synthesis from synthesis gas .

literature

• Heinz GO Becker among others: Organikum. 22nd edition. Wiley-VCH, Weinheim 2004, ISBN 3-527-31148-3 .

Individual evidence

1. ↑ ^{a b} data sheet Copper (II) tartrate hydrate (PDF) from Strem, accessed on December 25, 2012.
2. ↑ Data sheet Copper (II) tartrate hydrate from Sigma-Aldrich , accessed on April 7, 2011 ( PDF ).
3. ↑ ^{a b c} Fangfang Jian, Pusu Zhao, Qingxiang Wang: Synthesis and crystal structure of a novel tartrate copper (II) two-dimensional coordination polymer: {[Cu ₂ (C ₄ H ₄ O ₆ ) ₂ (H ₂ O) ₂ ] · 4H ₂ O} _∞ . In: J. Coord. Chem. 58, 2005, pp. 1133-1138, doi: 10.1080 / 00958970500148446 .
4. ^ ^{A b c} C. K. Prout, JR Carruthers, FJC Rossotti: Structure and stability of carboxylate complexes. Part VII. Crystal and molecular structures of copper (II) meso-tartrate trihydrate and copper (II) d-tartrate trihydrate. In: J. Chem. Soc. A, Inorg. Phys. Theo., 1971, pp. 3336-3342, doi: 10.1039 / J19710003336 .
5. ↑ ^{a b c} R. Weiss, S. Vukojevi, C. Baltes, R. Naumann d'Alnoncourt, M. Muhler, M. Epple : Copper / Zinc L-Tartrates: Mixed Crystals and Thermolysis to a Mixture of Copper Oxide and Zinc Oxide That Is Catalytically Active in Methanol Synthesis. In: Eur. J. Inorg. Chem. 2006, pp. 4782-4786, doi: 10.1002 / ejic.200600561 .
6. ↑ ^{a b c} I. Quasim, A. Firdous, B. Want, SK Khosa, P.. Kotru: Single crystal growth and characterization of pure and sodium-modified copper tartrate. In: J. Cryst. Growth. 310, 2008, pp. 5357-5363, doi: 10.1016 / j.jcrysgro.2008.09.021 .
7. ↑ ^{a b} N. D. Jespersen: Novel Copper-Tartrate Coordination Compounds. In: Anal. Let. 5, 1972, pp. 497-508.
8. ^ ^{A b} E. C. Rodrigues, CT Carvalho, AB de Siqueira, G. Bannach, M. Ionashiro: Synthesis, characterization and thermal behavior on solid tartrates of some bivalent metal ions. In: Thermochim. Acta . 496, 2009, pp. 156-160, doi: 10.1016 / j.tca.2009.07.015 .