# Naming compounds with an OX group

How are compounds which have a bond between an oxygen atom and a halogen atom named according to IUPAC rules? For example this compound:

I looked in many sites, but couldn't find how such compounds are named. Also what is their seniority compared to alcohols, esters, ketones, and carboxylic acids? Or are they always a prefix?

• These are esters, however this exact case is problematic. Also it wouldn't be stable. – Mithoron Apr 20 '16 at 16:07

The preferred IUPAC name (PIN) of the compound given in the question is butan-2-yl hypofluorite. It is named as ester of hypofluorous acid. In the seniority order of classes, esters are ranked between anhydrides and acid halides.

The corresponding subsection of the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) reads as follows:

P-67.1.3.2 Esters of mononuclear noncarbon oxoacids

Esters of mononuclear noncarbon acids are named in the same way as esters of organic acids (…). Alkyl groups, aryl groups, etc. are cited as separate words, in alphanumerical order when more than one, and followed by the name of the appropriate anion. Partial (acid) esters of polybasic acids are named by citing alkyl groups, aryl groups, etc. as separate words, in alphanumeric order if more than one, followed by the word ‘hydrogen’ (with the appropriate multiplying prefix, as necessary) also cited as a separate word, and the name of the appropriate anion. Salts of partial (acid esters) are named by citing the name of the cation before the name of the organic group; remaining acids groups are denoted by the word ‘hydrogen’ as described above. Structural specificity for esters of chalcogen analogues of mononuclear noncarbon oxoacids is provided by the appropriate italic element symbols O, S, Se, and Te, prefixed to the name of the group, as needed.

• But why is it an ester and not an ether? – indjev99 Apr 20 '16 at 20:22
• @indjev99 Ethers have the general formula $\ce{R-O-R'}$, in which $\ce{R}$ and $\ce{R'}$ are substituent groups derived from organic parent hydrides. – Loong Apr 21 '16 at 15:05

The are covalent hypohalogenites. Few are known to exist, such as methyl hypochlorite and tert-butyl hypochlorite. The one you have shown would be called sec-butyl hypofluorite, and is so unstable it likely cannot be isolated.

Due to the powerful oxidizing properties of these groups, such compounds are so unstable that they explosively decompose into toxic fumes, so you wouldn't have to worry about naming a multi-substituted compound. It would be difficult enough to form a compound with more than just a hypochlorite group without having severely altered the other functional groups, and any molecules that did form would react so violently with one another that it would probably be considered little more than a transition state.

• Note that the retained prefix ‘sec-butyl’ was still contained in the 1993 IUPAC recommendations, but it is no longer recommended in the 2013 recommendations. – Loong Apr 20 '16 at 16:37