por He copper sulphate It is an inorganic compound formed by the elements copper (Cu), sulfur (S) and oxygen (O). Its chemical formula is CuSO4. Copper is in the +2 oxidation state, sulfur is +6, and oxygen has a valence of -2.
It is a white solid that when exposed to ambient moisture converts to its blue pentahydrate CuSO4•5H2O. The white solid is obtained by heating the blue to remove the water.
It has been used as an antibacterial agent for centuries to heal wounds in humans and animals. It also works as a fungicide, as an astringent, antidiarrheal and to control intestinal diseases in animals. It is also used as an antifungal agent in plants.
However, some of its uses have been discontinued because its excess can be toxic to humans, animals, and plants. The range of concentrations in which it can be used is narrow and depends on the species.
It is used as a catalyst in chemical reactions and as a desiccant for solvents. It allows to improve the resistance and flexibility of some polymers.
Excessive amounts of this compound can be harmful in soils, as it is toxic to microorganisms that are beneficial to plants.
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Structure
Copper sulfate is made up of a copper ion (Cu2+) and a sulfate ion (SO42-).
Due to the loss of two electrons, the copper(II) ion has the following electronic conformation:
1s2 2s2 2p6 3s2 3p6 3d9
It can be seen that it has the orbital 3d incomplete (has 9 electrons instead of 10).
Nomenclature
Anhydrous copper sulfate
copper(II) sulfate
cupric sulfate
Properties
physical state
White or greenish-white solid in the form of crystals.
Molecular weight
159.61 g/mol
Melting point
At 560 ºC it decomposes.
Density
3.60 g/cm3
Solubility
22 g/100 g of water at 25 °C. Insoluble in ethanol.
Chemical properties
When subjected to air humidity below 30 °C it becomes the pentahydrate compound CuSO4•5H2O.
Its aqueous solutions are blue due to the formation of the hexaaquacopper(II) ion.[Cu(H2O)6]2+ which produces said coloration. In this ion two of the water molecules are farther from the metal atom than the other four.
This is due to the so-called Jahn-Teller effect, which predicts that this type of system experiences distortion caused by the fact that Cu2+ has an electronic structure that ends in d9, that is, an incomplete orbital (it would be complete if it were d10). .
If ammonia (NH3) is added to these solutions, complexes are formed in which the NH3 successively displaces the water molecules. They are formed, for example, from [Cu(NH3)(H2O)5]2+ until [Cu(NH3)4(H2O)2]2+.
When CuSO4 is heated to decomposition it emits toxic gases and turns into cupric oxide CuO.
Obtaining
Anhydrous copper sulfate can be obtained by total dehydration of the pentahydrate compound, which is achieved by heating it until the water molecules evaporate.
CuSO4•5H2O + heat → CuSO4 + 5 H2O↑
The pentahydrated compound is blue, so when the water of crystallization is lost, white anhydrous CuSO4 is obtained.
Applications
Some of its uses overlap with that of the pentahydrate compound. Others are specific to the anhydrous substance.
As an antibacterial agent
It has potential as an antimicrobial agent. It has been used for thousands of years, even in South and Central American cultures, to prevent wound infection with gauze soaked in a solution of this compound.
It is estimated that in the mechanism of its antibacterial activity, Cu2+ ions form chelates with enzymes that are crucial for the cellular functions of bacteria, deactivating them. They also induce the formation of OH• hydroxyl radicals, which damage the membranes of bacteria and their DNA.
It has recently been reported that CuSO4 traces can increase the antimicrobial activity of natural products rich in polyphenols, such as pomegranate extracts and infusions of some types of tea plants.
In veterinary applications
It is used as an antiseptic and astringent for mucous membranes and to treat conjunctivitis and otitis externa. It is used to carry out therapeutic or prophylactic baths to prevent rotting of the legs of cattle, sheep and other mammals.
It serves as a caustic agent for necrotic masses on the extremities of cattle, ulcers of stomatitis and granulated tissue of these. It has use as a fungicide in the treatment of ringworm and diseases caused by skin fungi.
It is also used as an emetic (agent to cause vomiting) in pigs, dogs and cats; as an antidiarrheal astringent for calves and to control intestinal thrush in poultry and trichomoniasis in turkeys.
As a supplement in animal feed
Copper sulfate has been used as a supplement in very small amounts in cattle, swine, and poultry feed. It is used to treat copper deficiency in ruminants. In the case of pigs and birds it is used as a growth stimulant.
Copper has been identified as essential for mammalian hemoglobin biosynthesis, cardiovascular structure, bone collagen synthesis, enzyme systems, and reproduction.
As mentioned in the previous section it can also be given as a disease control medication. However, supplementation and/or medication levels must be carefully monitored.
From a certain amount, which depends on each species, a decrease in growth, loss of appetite and weight, damage to certain organs and even death of the animals can occur.
For example, in chickens, supplementation of 0.2% or more decreases their food intake with the consequent loss of weight, decreased egg production and the thickness of their shells.
In agricultural applications
In organic production systems it is not allowed to use synthetic fungicides, only products based on copper and sulfur are accepted, such as copper sulfate.
For example, certain fungi that attack apple plants, such as Venturia inaequalis, are eliminated with this compound. It is thought that Cu2+ ions are possibly capable of entering the fungal spore, denaturing proteins and blocking various enzymes.
Importance of copper in plants
The element copper is important in plant physiological processes such as photosynthesis, respiration, and defense against antioxidants. Both the deficiency of this element and its excess generate reactive oxygenated species that are harmful to molecules and their structures.
The range of copper concentrations for optimum plant growth and development is very narrow.
Adverse effects on agriculture
When this product is used in excess in agricultural activities, it can be phytotoxic, cause premature development of the fruits and change their coloration.
Also, copper accumulates in the soil and is toxic to microorganisms and earthworms. This conflicts with the concept of organic agriculture.
In catalysis of chemical reactions
Anhydrous CuSO4 serves as a catalyst for various reactions of organic carbonyl compounds with diols or their epoxides, forming dioxolanes or acetonides. Thanks to this compound, reactions can be carried out under mild conditions.
It has also been reported that its catalytic action allows the dehydration of secondary, tertiary, benzylic and allylic alcohols to their corresponding olefins. The reaction is carried out very simply.
The pure alcohol is heated together with the anhydrous CuSO4 at a temperature of 100-160 °C for a period of 0.5-1.5 hours. The dehydration of the alcohol thus occurs and the olefin is distilled pure from the reaction mixture.
As a dehydrating agent
This compound is used in chemistry laboratories as a desiccant. It is used to dehydrate organic liquids such as solvents. It absorbs water, forming the pentahydrate compound CuSO4•5H2O.
To improve polymers
Anhydrous CuSO4 has been used to improve the properties of certain polymers while allowing them to be recyclable.
For example, particles of the compound in acetone have been mixed with acrylonitrile-butadiene rubber in a special mill, trying to make the CuSO4 particles very small.
Copper sulfate improves the bonding points of the polymer, forming a mixture with high resistance, hardness and surprising flexibility.
In discontinued therapeutic applications
In the past, copper sulfate solutions were used for gastric lavages when someone suffered from white phosphorus poisoning. However, the solution was promptly stirred to avoid copper poisoning.
Solutions of this compound were also used together with other substances for topical applications in phosphorus burns on the skin.
They were sometimes useful in certain forms of nutritional anemia in children and in copper deficiency in subjects receiving parenteral nutrition, that is, people who cannot feed themselves by mouth.
Certain lotions for eczema, impetigo and intertrigo contained CuSO4. The solutions were used as an astringent in eye infections. Sometimes the crystals were applied directly to burns or ulcers.
All these applications are no longer carried out due to the toxicity that the excess of this compound can induce.
References
US National Library of Medicine. (2019). Copper sulfate. Retrieved from pubchem.ncbi.nlm.nih.gov.
Lide, D.R. (editor) (2003). CRC Handbook of Chemistry and Physics. 85th CRC Press.
Montag, J. et al. (2006). An in Vitro Study on the Postinfection Activities of Copper Hydroxide and Copper Sulfate against Conidia of Venturia inaequalis. J. Agric. Food Chem. 2006, 54, 893-899. Retrieved from link.springer.com.
Holloway, AC et al. (2011). Enhancement of antimicrobial activities of whole and sub-fractionated white tea by addition of copper (II) sulphate and vitamin C against Staphylococcus aureus; a mechanistic approach. BMC Complement Altern Med 11, 115 (2011). Retrieved from bmccomplementmedtherapies.biomedcentral.com.
Sanz, A. et al. (2018). Copper uptake mechanism of Arabidopsis thaliana high-affinity COPT transporters. Protoplasm 256, 161-170 (2019). Retrieved from link.springer.com.
Griminger, P. (1977). Effect of copper sulfate on egg production and shell thickness. Poultry Science 56: 359-351, 1977. Retrieved from academic.oup.com.
Hanzlik, RP and Leinwetter, M. (1978). Reactions of Epoxides and Carbonyl Compounds Catalyzed by Anhydrous Copper Sulfate. J.Org. Chem., Vol.43, No.3, 1978. Retrieved from pubs.acs.org.
Okonkwo, AC et al. (1979). Copper Requirement of Baby Pigs Fed Purified Diets. The Journal of Nutrition, Volume 109, Issue 6, June 1979, Pages 939-948. Retrieved from academic.oup.com.
Hoffman, RV et al. (1979). Anhydrous Copper(II) Sulfate: An Efficient Catalyst for the Liquid-Phase Dehydration of Alcohols. J.Org. Chem., 1980, 45, 917-919. Retrieved from pubs.acs.org.
Shao, C. et al. (2018). Improved tensile strength of acrylonitrile-butadiene rubber/anhydrous copper sulfate composites prepared by…