Teflon tube crystallizers

A solution of 2-fluoroplienyllitliium (6 mmol, freshly prepared from 1 -bromo-2-fluorobenzene and butyllithium at —78°C) in anhydrous diethyl ether was fed through a small Teflon tube into a stirred suspension of triphenylbismuth dichloride (3 mmol) in the same solvent (20 ml) cooled to —78°C. The resulting suspension was gradually warmed to room temperature under stirring. After decanting from deposited lithium chloride, the clear red-violet solution was carefully evaporated. Crystallization at 0°C afforded bis(2-fluorophenyl)triphenylbismuth (45%), which is readily soluble in ether, but insoluble in pentane and sensitive to hydrolysis [90AG(E)213]. 

To a solution of pentaphenylbismuth (0.67 mmol) in THF (12 ml) was added a solution of phenyllithium (1.4 mmol) in diethyl ether/cyclohexane (7 3) at —78°C. When the resulting yellow suspension was wanned to room temperature, the color turned blue-violet. The solution was pressed with argon through a thin Teflon tube into a glass ampule, that was then sealed off. Crystallization of the yellow bismuthinate, Li [BiPh ]-THF, occurred in the ampule on cooling to 0-18°C [93IC3948]. 

Figure 5.21 shows a surface-cooled crystallizer that utilizes Teflon tubes as the heat exchanger media. The Teflon tubes... 

SWENSON TEFLON TUBE CRYSTALLIZER Figure 5.21 Swenson Teflon tube crystallizer. 

Example 16.5. Teflon heat transfer tubes that are thin enough to flex under the influence of circulating liquid cause a continual descaling that maintains good heat transfer consistently, 20-65 Btu/(hr)(sqft)(°F). Circulating types such as Figures (d) and (e) of ten are operated in batch mode, the former under vacuum if needed. High labor costs keep application of batch crystallizers to small or specialty production. 

Xenon(II) bis(oxopentafluoroselenate(VI)) was prepared from xenon difluoride and pentafluoroselenic acid, HOSeFs, as previously described. Crystals were grown by sublimation in Teflon FTP tubing under dynamic vacuum. Raman spectra of the crystals studied established that they were representative of the bulk material. The hydrolytically unstable crystals, which were pale yellow tablets, were loaded in a nitrc en-filled Vacuum Atmospheres Drilab, into 0.2-mm diameter thin-walled quartz capillaries. The capillaries were sealed in a small flame. 

Fig. 10.8 Thin-layer electrochemical cell used in SNIFTIR studies and reflection optics (a) Teflon cap (b) N2 inlet (c) glass tube (d) Teflon cell body (e) port for reference electrode (f) ceramic tube (g) Pt wire counter electrode (h) single crystal working electrode (i) hemispherical ZnSe window (k) focal plane for reflection optics (m) instrument focal plane and (n) folding mirrors (From reference 16, with permission.)...

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