Hypofluorous acid, HOF

HOF was first prepared and isolated at the beginning of the 1970s by passing fluorine over cold water. At low temperature, HOF is a white solid that melts at -117°C forming a pale yellow liquid and boils below room temperature. The compound has a strong tendency to decompose into HF and O2. 

Throughout this chapter, the formula of the compound is written as HOF in accordance with the structure of the molecule where the central atom is oxygen. Two isomeric forms, HFO (bent) and FHO (linear) were predicted and are treated in Chapter 3.25, p. 157. 

A review on HOF is contained in the article on fluorinated hypofluorites and hypochlorites by J. M. Shreeve (Advan. Inorg. Chem. Radiochem. 26 [1983] 119/68, 121/3). 

A very similar process then results in the reduction of halite (XO2 ) to hypohalous acid (HOX), while producing the second molecule of X2  

Proton-coupled attack by halide on the hypohalous acid then produces the third and final molecule of X2  

A heterolytic mechanism, analogous to the reaction of chlorine or bromine with water, may be envisioned as follows  

The F-F bond is so weak, however, that a homolytic (radical) path mediated by fluorine atoms is also a possibility  

The process may be viewed as a chain reaction, where the first step is the radical initiation, the second and the third steps are propagation, and the last step is radical termination. 

Fluorine is unique among the halogens in forming no species in which it has a formal oxidation state other than — 1. The only known oxoacid is hypofluorous acid, HOF, which is unstable and does not ionize in water but reacts according to equation 16.54 no salts are known. It is obtained by passing F2 over ice at 230 K (equation 16.55) and condensing the gas produced. At 298 K, HOF decomposes rapidly (equation 16.56). 

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Hypofluorous acid, HOF, is extremely unstable at room temperature. The fallowing data apply to the decomposition of HOF to HF and 03 gases at a certain temperature. 

Perhaps the best demonstration of the unwillingness of covalently bonded fluorine to participate in hydrogen bonding is hypofluorous acid, HOF. This... 

The reaction of fluorine with water, producing hypofluorous acid (HOF) and subsequently oxygen difluoride (OF2), has been the subject of intensive study over the last fifty years.1 Additionally, hypofluorous acid in acetonitrile has been characterized.5 The reagents are potentially explosive and present a toxicity hazard similar to fluorine therefore, work should be carried out in an efficient hood and proper safety equipment is required. It was established in the earliest investigations that the reaction of hypofluorous acid with alkenes in nonpolar solvents gives fluoro hydrins, e.g. 1, in high yield.6 However, it is now clear that epoxides are initially formed in acetonitrile7 and 1,2-epoxycyclohexane (2) is formed in reactions with cyclohexene in various solvents.5... 

At room temperature hypofluorous acid HOF is a gas. Its colorless solid (mp = 156 K) melts to a pale yellow liquid. In the crystal structure, O-F = 144.2 pm, angle H-O-F =101°, and the HOF molecules are linked by O-H- O hydrogen bonds (bond length 289.5 pm and bond angle O-H- O 163°) to form a planar zigzag chain, as shown below ... 

In some cases, this has been shown to be a consequence of the very high chemical reactivity of the molecules. Thus hypofluorous acid, HOF, has never been isolated. It was not until 1967 that its short-lived presence was detected spectroscopically. It is now believed that the molecule is stable, but that the products obtained when it reacts with itself are so much more stable that it decomposes almost as fast as it is formed ... 

Hypofluorous Acid. Hypofluorous acid (HOF) may be prepared by passing fluorine over water in a Kel-F reactor at 0 °C (equation 76).i ... 

Fluorine forms only one oxyacid, hypofluorous acid (HOF), but it forms at least two oxides. When fluorine gas is bubbled into a dilute solution of sodium hydroxide, the compound oxygen difluoride (OF2) is formed ... 

An easily prepared acetonitrile complex of hypofluorous acid (HOF-CH3CN) serves an excellent reagent for the oxidation of alkenes with pendant alcohol or carboxylic acid functionalities <1996TL531>. 

Hydrogen fluoride (UF) Hypofluorous acid (HOF) Fluorosulfuric acid (HSO F) Fluorosilane (SiH F)... 

Fluorination of ice yields milligram amounts of hypofluorous acid, HOF, which is unstable at RT . Solutions of the other hypohalous acids and hypohalites are formed via disproportionative hydrolysis of the halogens ... 

The only oxoacid of fluorine that has been prepared is unstable hypofluorous acid, HOF. Aqueous hypohalous acids (except HOF) can be prepared by reaction of free halogens (CI2, Br2, I2) with cold water. The smaller the halogen, the farther to the right the equilibrium lies. 

Oxygen difluoride, OF2 (15.21), is highly toxic and may be prepared by reaction 15.47. Selected properties are given in Table 15.5. Although OF2 is formally the anhydride of hypofluorous acid, HOF, only reaction 15.48 occurs with water and this is very slow at 298 K. With concentrated alkali, decomposition is much faster, and with steam, it is explosive. 

Hypofluorous acid, HOF. Mol. wt. 35.01 unstable above 77 K. The material is prepared in small quantities (caution) by the reaction of fluorine with ice at — 40° in a special apparatus. ... 

The reaction of F atoms with hypofluorous acid (HOF) has recently been reported by Appelman and Oyne to be a source of the OF radical, previously only... 

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