quality:correction
Organic and main group chemistry

In the presence of strong acids, alkenes react with carboxylic acids. Hydrolysis of this species (an acylium ion) gives the carboxylic acid, a net process known as the Koch–Haaf reaction. In the Gattermann–Koch reaction, arenes are converted to benzaldehyde derivatives in the presence of CO, AlCl, and HCl.

A mixture of hydrogen gas and CO reacts with alkenes to give aldehydes. The process requires the presence of metal catalysts.

With main group reagents, CO undergoes several noteworthy reactions. Chlorination of CO is the industrial route to the important compound phosgene. With borane CO forms the adduct H BCO, which is isoelectronic with the acylium cation. CO reacts with sodium to give products resulting from C−C coupling such as sodium acetylenediolate 2 Na · C O. It reacts with molten potassium to give a mixture of an organometallic compound, potassium acetylenediolate 2 K · C O, potassium benzenehexolate 6 K C O, and potassium rhodizonate 2 K · C O.

The compounds cyclohexanehexone or triquinoyl (C O) and cyclopentanepentone or leuconic acid (C O), which so far have been obtained only in trace amounts, can be regarded as polymers of carbon monoxide. At pressures exceeding 5 GPa, carbon monoxide converts to polycarbonyl, a solid polymer that is metastable at atmospheric pressure but is explosive.