A polycarbonate is an oxocarbon dianion consisting of a chain of

carbonate A carbonate is a salt of carbonic acid, (), 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 carbonate group ...

units, where successive

carbonyl group In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes ...

s are directly linked to each other by shared additional

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

atoms. That is, they are the

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid gives a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as it loses a hydrogen ion in the reve ...

s of polycarbonic acids, the conceptual

anhydride An acid anhydride is a type of chemical compound derived by the removal of water molecules from an acid (chemistry), acid. In organic chemistry, organic acid anhydrides contain the functional group . Organic acid anhydrides often form when one ...

s of

carbonic acid Carbonic acid is a chemical compound with the chemical formula . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion ...

, or polymers of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

. They have the structure ^–O C=O)–Osub>''n''^– and the molecular formula _nO_2''n''+1sup>2–. Whereas the carbonate dianion itself is well known, as found in many

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

s, many

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

compounds containing

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s of it have been made, and the parent

is also well-known, higher

homolog In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained her ...

s are substantially less stable. Only a few examples of covalent

dicarbonate A dicarbonate, also known as a pyrocarbonate, is a chemical containing the divalent or functional group, which consists of two carbonate groups sharing an oxygen atom. It is one of polycarbonate functional groups. These compounds can be vi ...

and

tricarbonate In organic chemistry, a tricarbonate is a compound containing the divalent functional group, which consists of three carbonate groups linked in a chain by sharing of oxygen atoms. These compounds can be viewed as derivatives of a hypothetical tri ...

structures and ionic dicarbonate salts have been made and their

conjugate acid A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid gives a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as it loses a hydrogen ion in the rever ...

s have only been studied theoretically. Polycarbonates up to ''n''=6 have been studied theoretically, with the dianions being only

metastable In chemistry and physics, metastability is an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball is onl ...

but stabilized when paired with metal

counterion 160px, cation-exchange_resin.html" ;"title="Polystyrene sulfonate, a cation-exchange resin">Polystyrene sulfonate, a cation-exchange resin, is typically supplied with as the counterion. In chemistry, a counterion (sometimes written as "counter ...

s or as their conjugate acids. Di-''tert''-butyl tricarbonate extrudes

in the presence of various

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

s to form di-''tert''-butyl dicarbonate. Long-chain carbon dioxide oligomers are likewise expected to decompose

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...

ally.

References

Oxyanions Oxocarbons {{inorganic-compound-stub