Fluoroimidodisulfuryl fluoride

A standard Pyrex vacuum apparatus is employed in this preparation. The system includes a fractionation train consisting of four U-tube traps, attached with ball joints, a mercury manometer, and several ball-joint connections on the manifold. The mercury in the manometer is covered with outgassed Kel-F-10 oil, and the stopcocks and ball joints are lubricated with Kel-F-90 grease. The fluorine metering system consists of a fluorine tank properly shielded and vented, a sodium fluoride scrubber (45 X 13 cm.), two calibrated rotameters for measuring flow rate and fluorine concentration, and a helium source, and is constructed of -J-in. copper tubing. 

Imidodisulfuryl fluoride,f 18.5 g. (0.102 mole), is loaded into a Pyrex U-tube containing a small magnetic stirring bar. The U-tube is attached to the fractionation train on the vacuum line, and the train is flushed with helium. The two adjacent U-tubes are cooled to —78°, and the last U-tube is cooled to —196°. The two —78° traps should be packed with Pyrex helices to ensure efficient trapping. The fluorine tank is opened, and the concentration of fluorine is adjusted to approximately 30%. The helium-diluted fluorine is passed over the surface of the imidodisulfuryl fluoride at ambient temperature and at a flow rate of 150-175 ml./minute for appro.ximately 2 hours or until most of the imidodisulfuryl fluoride has disappeared from the U-tube. After the fluorination is finished, the system is flushed for 15 minutes with helium and then evacuated. The contents of the two —78° traps [crude FN(SOiF)2] are combined. Final purification is achieved by slow fractionation through U-tubes maintained at —33° (bromobenzene slush) and —78°. The former trap retains approximately 1 g. of imidodisulfuryl fluoride the —78° trap collects 15.3 g. (75% yield) of fluoroimido-disulfuryl fluoride. Anal. Calcd. for FN(SO F)2 N, 7.03 S, 32.3 F, 28.6. Found N, 7.11 S, 32.7 F, 28.8. 

Fluoroimidodisulfuryl fluoride melts at —79.9 + 0.3° and boils at 60.8 1.0°. The liquid-vapor equilibrium pressure above 80 mm. is given by the Clausius-Clapeyron equation, log P(mm.) = 7.980 — 1703/T. Its Trouton constant (e.u.) and latent heat of vaporization (kcal./mole) are 23.3 and 7.80, respectively. Its vapor-density molecular weight has been measured to be 203 (calcd. 199). The infrared spectrum shows absorptions at 1495(vs), 1247(vs), 1020(m), 997(vs), 849(vs), 660(m), and 562(vs) cm.. The n.m.r. absorptions for FN(SO F)j are located at —44.9 and 28.5 p.p.m. (from CCUF). When in contact with dilute aqueous base, FN(S02F) hydrolyzes substantially in the following way  

Submitted by FREDERICK A. HOHORST and JEAN NE M. SHREEVE Cheeked by STANLEY M. WILLIAMSONf 

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IMIDODISULFXJRYL FLUORIDE, CESIUM IMIDODISULFURYL FLUORIDE, AND FLUOROIMIDODISULFURYL FLUORIDE... 

This purification process is particularly important if the imidodisulfuryl fluoride is to be used in the preparation of fluoroimidodisulfuryl fluoride since the fluorination of imido-disulfuryl fluoride which contains small amounts of fluorosulfuric acid does not occur under the conditions to be described. However, if imidodisulfuryl fluoride is to be converted to one of the alkali metal salts, this purification step is not necessary. 

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