Sulfur tetrafluoride oxide

Sulfur tetrafluoride oxide is the only stable sulfur fluoride or sulfur fluoride oxide that is not commercially available, although its value is increasing in synthetic chemistry. It was first made by burning SOF2 in elemental fluorine,1 

The method presented here avoids all these problems. If the reaction is run at 300° with a small excess of BrFs, the product contains only traces of SF6, S02F2, and SOF2.3 

Bromine pentafluoride, which is commercially available from Baker Chemicals, Phillipsburg, NJ, or Union Carbide Corp., may be used as such with the typical impurity of several percent bromine. It should be handled in a metal vacuum line.4 Standard glass vacuum lines with Kel-F greased valves have also been used, but this technique results in a SiF4 impurity. Sulfinyl difluoride, if not available, is best prepared from SOCl2 and NaF in CH3CN at 70° and by redistillation of the product at -43°. This method can be used on the 100-500 g scale. 

Sulfinyl difluoride (64.5 g, 0.75 mole) and bromine pentafluoride (55.0 g, 0.31 mole) are condensed into a 300-mL stainless steel container. The pressure vessel is heated for 8-14 hr with the temperature held as close to 300° as possible. The pressure reaches about 70-90 atm (1000-1300 psi). The pressure vessel is cooled to -78°, and all volatile substances are pumped out in a dynamic vacuum into a glass trap cooled to -196°. The bulk of bromine remains in the autoclave with small amounts of bromine trifluoride. The volatile materials, essentially pure SOF4, are purified from bromine by conventional trap-to-trap distillation. The impure sample is held at -100°, and the volatiles are collected at -196°. 

Sulfur tetrafluoride oxide is best stored in a stainless steel pressure vessel. Addition of a few grams of dry mercury removes the last traces of bromine. Another way to separate the SOF4/Br2 mixture is by low-temperature distillation through a 70-cm column. Yield 79 g (85%). 

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Caution. These materials must not be allowed to contact the skin. Bromine pentafluoride is an extremely reactive and very dangerous material. Silicone grease, or any other organic material, will cause explosions if contacted with BrFs. Sulfur tetrafluoride oxide is very poisonous. Any exposure of the reagents to moist air should be avoided. 

Sulfur tetrafluoride oxide is a colorless gas, mp -99.6°, bp -48.5°. Hydrolysis to S02F2 is rapid. This compound has a trigonal-bipyramidal structure with the... 

Sulfur tetrafluoride reacts with most inorganic oxides and sulfides to give the corresponding fluorides (103) ... 

Trifluoromethylpyridine can be prepared ia 54% yield from picolinic acid and sulfur tetrafluoride—hydrogen fluoride (434). 2-Trifluoromethylpyridine is a weak base no hydrochloride salt is formed. However, 2-trifluoromethylpyridine 1-oxide [22253-71-0] (bp 132—133°C/2.7 kPa (20 mm Hg)) is prepared ia 81% yield usiag 30% hydrogen peroxide—acetic acid (438). 

These reactions differ from those of sulfur tetrafluoride with carbonyl compounds in that a formal oxidation-reduction of the sulfur atoms m the thiocarbonyl compound and sulfur tetrafluoride molecule occurs, resulting in the formation of free sulfur and the complete utilization of the fluorine atoms in sulfur tetrafluoride. 

A series of reactions with gases have been selected for the rapid quantification of many of the major products from the oxidation of polyolefins. Infrared spectroscopy is used to measure absorptions after gas treatments. The gases used and the groups quantified include phosgene to convert alcohols and hydroperoxides to chloroformates, diazomethane to convert acids and peracids to their respective methyl esters, sulfur tetrafluoride to convert acids to acid fluorides and nitric oxide to convert alcohols and hydroperoxides to nitrites and nitrates respectively. 

In some cases it is possible to differentiate between the various alkyl substituents. Primary, secondary and tertiary nitrates and nitrites all show clearly different infrared absorptions. The spectra of acid fluorides can be used to differentiate chain-end groups from pendant acid groups. Furthermore, the loss of all -OH species upon sulfur tetrafluoride exposure allows the reliable estimation of ketones, esters and lactones without the complication of hydrogen-bonding induced shifts in the spectra. Preliminary results from the use of these reactions to characterize y-ray oxidized polyethylene and polypropylene are used to illustrate the scope of the methods. 

Thiadiazole oxides and reduced forms are readily prepared via [4 -h 1] cyclizations (Table 4). The reagents employed for this purpose are thionyl chloride, sulfuryl chloride, sulfur tetrafluoride, N,N -bis(p-toluenesulfonyl)sulfur diimide, cyclic diimides, pentafluoroethyliminosulfur difluoride and sulfamide. 

Conversion of tertiary formamides into A-(trifluoromethyl)amines involves a reduction-oxidation process in which sulfur tetrafluoride is reduced to elemental sulfur.175 Both /V,/V-dial-kyldifluoro(phenyl)methy la mines and A -(trifluoromethyl)amines are mild fluorinating reagents for the replacement of hydroxy groups by fluorine.176... 

Treatment of perhalogenated and highly halogenated alkenes with sulfur tetrafluoride in the presence of lead(IV) oxide, which is most likely converted in situ into lead(IV) fluoride, results in addition of fluorine to the C = C bond of the alkenes. The addition proceeds at 100 C to afford per- and polyhalogenated alkanes 5 in yields ranging from a few percent to almost quantitative.190 Representative examples are given. 

Sulfur tetrafluoride undergoes oxidative incorporation into a number of compounds of high oxidation state to form six-coordinated sulfur fluorides. Thus, reaction with bis(trifluorometh-yl)nitrogen oxide proceeds at ambient temperature and gives bis [bis(trifluoromethyl)amino]-oxy sulfur tetrafluoride (9) almost quantitatively.214... 

Sulfur tetrafluoride acts as an oxidative fluorinating agent towards organometalloid compounds. Triphenylphosphane and triphenylarsane are converted at 100-150C into difluoro-triphenyl-l5-phosphane (16) and difluorotriphenyl-l5-arsane (17), respectively.219... 

Similarly, the reaction between sulfur tetrafluoride and tris(dimethylamino)phosphane proceeds with oxidation of the phosphane in addition to fluorine transfer to give tris(dimethylamino)-difluoro-A5-phosphane (18) as the main product. In contrast, the reaction with tris(methyl-sulfanyl)phosphane does not give a straightforward fluorination extensive Arbuzov-type rearrangements and fluorination reactions occur.220... 

Oxygen functionalities bonded to a metalloid are replaced by fluorine when reacted with sulfur tetrafluoride. Triphenylphosphane oxide, phenylarsenic acid,219 and triphcnylantimony oxide and its bis(trifluoroacetoxy) derivative222 can be converted by sulfur tetrafluoride into the corresponding organophosphorus, organoarsenic and organoantimony fluorides 16,20 and 21. 

Trifluorodi(phenyl)-/.5-stibane (4) and difluorotri(phenyl)-25-stibane (6) arc less reactive in the chlorine-fluorine exchange.104 They are obtained by reacting diphenylstibinie acid (3) and triphenylstibane oxide (5) or triphenylbis(trifluoroaeetoxy)-A5-stibane (7) with sulfur tetrafluoride.105... 

Deep fluormation using the La-Mar technique was carried out on polymers such as polyethylene and polypropylene [/ ], on polyethers [19, 20, 21], and on polyesters subsequently treated with sulfur tetrafluoride [22] Deep fluorinations carried out under conditions producing limited fragmentation produced oligomeric perlluoropolyethers from powdered polyethylene oxide [23] Deep fluorinations carried out in the limited presence of molecular oxygen result m the conversion of... 

The most common compounds from the naphtho[crf]pyran series are naphthalic anhydride and its various derivatives 378 substituted in the naphthalene nucleus. These derivatives are formed on heating naphthalic acids 377, which are obtained on oxidation of the corresponding acenaph-thenes. The syntheses of naphthalic acids 377 and their anhydrides are described in a monograph (66MI1). The interaction between naphthalic acid and sulfur tetrafluoride leads to 2,2,9,9-tetrafluoronaphtho[cd]pyran 379 (73ZOR689). 

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