What is "hypofluorous acid"

n. (context chemistry English) the oxyacid of fluorine, HOF; a short-lived species that has only been observed spectroscopically

Hypofluorous acid is the chemical compound with the formula HOF. It is an intermediate in the oxidation of water by fluorine, which produces hydrogen fluoride and oxygen. It is the only hypohalous acid that can be isolated as a solid. HOF is explosive, decomposing to oxygen and HF. It was isolated in the pure form by fluorination of ice.

The compound has been characterized in the solid phase by X-ray crystallography as a bent molecule with an angle of 101°. The O–F and O–H bond lengths are 144.2 and 96.4 picometres, respectively. The solid framework consists of chains with O–H···O linkages. The structure has also been analyzed in the gas phase, a state in which the H–O–F bond angle is slightly narrower (97.2°).

For fluorine, the only known oxoacid is hypofluorous acid, HOF. It can be made by passing F gas over ice at −40 °C, collecting the HOF gas, and condensing it:

F + HO → HOF + HF

It decomposes explosively at room temperature to form HF and O:

2 HOF → 2 HF + O

Hypofluorous acid in acetonitrile (generated in situ by passing gaseous fluorine through "wet" acetonitrile) serves as a highly electrophilic oxygen-transfer agent. Treating phenanthroline with this reagent yielded the previously elusive 1,10-phenanthroline dioxide, more than 50 years after the first unsuccessful attempt.

This molecule is not very symmetric since the atoms are all different. It only has two symmetry operations: identity (E) and a mirror plane that goes through the three atoms. The assigned point group is C.