In chemistry, peroxydicarbonate (sometimes peroxodicarbonate) is a

divalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of a ...

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

with the chemical formula . It is one of the

oxocarbon anion In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula for some integers ''x'', ''y'', and ''n''. The most common oxocarbon anions are carbonate, , and oxalat ...

s, which consist solely of

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

. Its molecular structure can be viewed as two

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonat ...

anions joined so as to form a

peroxide In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable. The most common peroxide is hydrogen ...

bridge –O–O–. The anion is formed, together with peroxocarbonate , at the negative

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials ...

during electrolysis of molten

lithium carbonate Lithium carbonate is an inorganic compound, the lithium salt of carbonate with the formula . This white salt is widely used in the processing of metal oxides. It is listed on the World Health Organization's List of Essential Medicines because it ...

. The anion can also be obtained by electrolysis of a saturated solution of

rubidium carbonate Rubidium carbonate, Rb2CO3, is a convenient compound of rubidium; it is stable, not particularly reactive, and readily soluble in water, and is the form in which rubidium is usually sold. Preparation This salt can be prepared by adding ammonium c ...

in water. In addition, the peroxodicarbonate anion can be obtained by

electrosynthesis Electrosynthesis in chemistry is the synthesis of chemical compounds in an electrochemical cell. Compared to ordinary redox reaction, electrosynthesis sometimes offers improved selectivity and yields. Electrosynthesis is actively studied as a scie ...

boron doped diamond Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the '' boron group'' it has ...

(BDD) during water oxidation. The formal

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

of two carbonate ions takes place at the anode. Due to the high oxidation potential of the peroxodicarbonate anion, a high anodic overpotential is necessary. This is even more important if

hydroxyl radical The hydroxyl radical is the diatomic molecule . The hydroxyl radical is very stable as a dilute gas, but it decays very rapidly in the condensed phase. It is pervasive in some situations. Most notably the hydroxyl radicals are produced from the ...

s are involved in the formation process. Recent publications show that a concentration of 282 mmol/L of peroxodicarbonate can be reached in an undivided cell with sodium carbonate as starting material at current densities of 720 mA/cm². The described process is suitable for the pilot scale production of sodium peroxodicarbonate. Potassium peroxydicarbonate K₂C₂O₆ was obtained by Constam and von Hansen in 1895; its crystal structure was determined only in 2002. It too can be obtained by electrolysis of a saturated potassium carbonate solution at −20 °C. It is a light blue crystalline solid that decomposes at 141 °C, releasing

and carbon dioxide, and decomposes slowly at lower temperatures. Rubidium peroxodicarbonate is a light blue crystalline solid that decomposes at . Its structure was published in 2003. In both salts, each of the two carbonate units is planar. In the

rubidium Rubidium is the chemical element with the symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have a density hig ...

salt the whole molecule is planar, whereas in the

potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosp ...

salt the two units lie on different and nearly perpendicular planes, both of which contain the O–O bond.

References

Oxyanions Oxocarbons Physical chemistry {{physical-chemistry-stub

See also

References