Xenon hydrolysis reactions

Much of the chemistry of the xenon fluorides centers on their reactions with aqueous solutions. Owing to its greater ionic character, the reaction of XeF2 with water is much slower than those of XeF4 and XeF6. In fact, XeF2 can be dissolved in water to produce relatively stable solutions. The slow hydrolysis reaction of XeF2 can be shown as follows ... 

Xenon difluoride dissolves in water, yielding a solution which contains undissociated XeFa molecules which have a half-life of about 7 hours at 0°. It eventually hydrolyzes to yield the expected products, xenon, hydrogen fluoride, and oxygen. The hydrolysis reactions of the tetrafluoride and hexafluoride are somewhat more complicated. The addition of the stoichiometric amount of water to the hexafluoride results in the formation of xenon oxide tetrafluoride. Hydrolysis of either fluoride with an excess of water or acid yields in solution a stable xenon(VI) species, which has been shown to be hydrated xenon trioxide. Removal of the excess water leaves xenon trioxide as a solid residue. Inasmuch as this solid is an extremely sensitive explosive, such solutions must be handled with care. 

The xenon hexafluoride for this synthesis is best prepared by reaction of xenon with an excess of fluorine at 300° in a nickel or Monel apparatus. Extremely pure XeFs is not required. Xenon hexafluoride attacks glass, and should be stored in a nickel or Monel container until ready for use. The hydrolysis reaction is violent, and if more than a hundred milligrams of XeFe is to be hydrolyzed, special safety precautions must be taken. Face shields, heavy gloves, and a sturdy plastic explosion barrier between the hydrolysis apparatus and the experimenter are strongly recommended. No more than about 3 g. of XeFg should be hydrolyzed in one batch. 

The reaction of phenol with aqueous xenon difluoride has been investigated at pH 3—4, the primary stable product being p-benzoquinone. Under these conditions, the rate of consumption of XeFg in water is independent of the substrate present. The initial hydrolysis reaction is followed by a series of rapid redox steps depending on the substrate present ... 

At 0 °C, this reaction takes many hours for completion. With XeF, the oxidation of water, although thermodynamically very favourable, is again slow, and a rapid hydrolysis reaction occurs instead, yielding xenon trioxide ... 

Oxides. Two oxides of xenon are known xenon trioxide [13776-58-4], XeO, and xenon tetroxide [12340-14-6], XeO (Table 1). Xenon trioxide is most efftcientiy prepared by the hydrolysis of XeE (47) or by the reaction of XeE with HOPOE2 (48). The XeO molecule has a trigonal pyramidal shape Xe—O, 176(3) pm (49), and XeO is tetrahedral with Xe—O, 173.6(2) pm (50). Xenon tetroxide is prepared by the interaction of concentrated sulfuric acid with sodium or barium perxenate, Na XeO, Ba2XeO ( )- Both oxides are thermodynamically unstable, explosive soHds which must be... 

Although uncontrolled reaction of xenon hexafluoride and moisture produces explosive xenon trioxide, controlled action by progressive addition of limited amounts of water vapour with agitation to a frozen solution of the hexafluoride in anhydrous hydrogen fluoride at —196° C to give xenon oxide tetrafluoride or xenon dioxide difluoride is safe [1], Controlled hydrolysis in solution in hydrogen fluoride is, however, described as hazardous [2],... 

Xenon also forms compounds, possibly clatlirates. with certain substances in nonstoichiometric proportions. Crystalline compounds with benzene or hydroquinone, formed under 40 aim osp lie res pressure, contain about 26% xenon by weight. Alkaline hydrolysis of XeF6 produces salts of octavalent xenon. No persistent divalent or tetravalent compounds are found in aqueous solution, but the former is intermediate in hydrolysis of the fluondes, and the latter in reactions of XeC>3 with XeF2, Hi02, and various organics... 

Korytnyk and coworkers have shown that reactions of xenon difluoride with acetylated glycals in the presence of boron trifluoride are a convenient route for the synthesis of 1,2-difluoro sugars, while the addition of fluorine to the double bond occurred predominantly from the less hindered side and cis adducts were mainly formed75, 76. Stereoselective transformation of tri-O-acetyl-D-galactal with xenon difluoride at -20 to +5 °C, without a catalyst in CFC13, after hydrolysis, afforded 2-deoxy-2-fluoro-D-galactose in 63% yield77. 

Xenon oxides are prepared from the fluorides. As has already been mentioned, hydrolysis of XeF4 and XeF6 leads to the formation of Xe03 by reactions that can be shown as... 

XeOp4 was first detected as an impurity by mass spectrometry among the xenon fluorides prepared by thermal methods. It was obtained in macroscopic quantities by the partial hydrolysis of xenon hexafluoride (equation 7). Umeacted XeFe and HF formed in the reaction are removed... 

Xe02p2 was observed in the early mass spectra of xenon fluorides and can be obtained by hydrolysis of XeFe. The best method for its preparation in macroscopic quantities is by the reaction of XeOs and XeOp4. The XeOp4 and Xep2 impurities may be removed by fractional distillation. Xenon dioxide difluoride forms colorless crystals at room temperature, which have a vapor pressure between that of XeOs and XeOp4 and melts at 303.95 K to give a colorless liquid. It can decompose to Xep2 and O2. 

Xenon.—Several studies have been reported by Russian workers on the reactions of xenon difluoride in aqueous solution. The oxidation of phenol to p-benzo-quinone is suggested to involve an intermediate in the hydrolysis of xenon difluoride, possibly xenon monoxide. The rate of disappearance of xenon difluoride in the presence of phenol is the same as the rate of hydrolysis in the absence of the latter. A competition method has been used to study the role of this postulated intermediate. The kinetics of reaction of xenon difluoride with 2,3,6,6-tetramethylpiperidin-l-oxyl have been studied. In a review of recent developments in the chemistry of some electronegative elements there is a brief summary of fluxional behaviour in the proposed tetramer of XeF in solution. ... 

Previous suggestions on the mechanism of hydrolysis of xenon difluoride have been confirmed/ The first intermediate is XeO, which interacts with water to give hydrogen peroxide. Oxidation of hydrogen peroxide by Xep2 has already been investigated, and involves a chain reaction initiated by reaction between XeO and H2O2. 

The xenon fluorides were synthesized by the direct reaction of the element shortly after Bartlett s announcement. The tetrafluoride is the stablest and best characterized, although its hydrolysis yields the dangerously explosive xenon trioxide. Xenon difluoride is an excellent oxidizing agent and fluoride ion donor. Xenon hexafluoride is both a fluoride donor and acceptor. 

Analyze the change in oxidation numbers for the hydrolysis of xenon tetrafluoride found in Equation (19.5), repeated below. Identify the oxidizing and reducing agents in this reaction. 

A bicyclic iodoxole oxide 236, the aliphatic analog of IBX, has been prepared by the fluorination of 1,2-iodoxetane 205 (see Section 3.2.9) with xenon difluoride followed by a hydrolysis of the intermediate, non-isolable, difluoride 235 (Scheme 52 2004TL8173). Compound 236 has reactivity similar to IBX and can oxidize alcohols and sulfides to the corresponding carbonyl compounds and sulfoxides, respectively, in good yields under mild reaction conditions. 

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