Radialene-type Cyclic Polyketones
Another family of oxocarbons that has attracted special attention are the cyclic radialene-type oxocarbons CnOn or (CO)n. They can be regarded as cyclic polymers of carbon monoxide, or n-fold ketones of n-carbon cycloalkanes. Carbon monoxide itself (CO) can be regarded as the first member. Theoretical studies indicate that ethylene dione (C2O2 or O=C=C=O) and cyclopropanetrione C3O3 do not exist. The next three members — C4O4, C5O5, and C6O6 — are theoretically possible, but are expected to be quite unstable, and so far they have been synthesized only in trace amounts.
| (CO)2 Ethylene dione |
(CO)3 Cyclopropane- trione |
(CO)4 Cyclobutane- tetrone |
(CO)5 Cyclopentane- pentone |
(CO)6 Cyclohexane hexone |
On the other hand, the anions of these oxocarbons are quite stable, and some of them have been known since the 19th century. They are
- C2O22−, acetylenediolate (Weiss and Büchner, 1963),
- C3O32−, deltate (Eggerding and West, 1976),
- C4O42−, squarate (Cohen and others, 1959),
- C5O52−, croconate (Gmelin, 1825), and
- C6O62−, rhodizonate (Heller, 1837).
The cyclic oxide C6O6 also forms the stable anions of tetrahydroxy-1,4-benzoquinone (C6O64−) and benzenehexol (C6O66−), The aromaticity of these anions has been studied using theoretical methods.
Read more about this topic: Oxides Of Carbon