Vacuum transfer apparatus

Figure A. Flex tubing connected vacuum transfer apparatus. Continued on next page.

Vacuum transfer apparatus (e.g., Millipore Milliblot V or LKB Vacugene 2016) plus adjustable vacuum pump (e.g., Millipore VacI or LKB 2016 Vacugene pump). 

The volatile materials are transferred under essentially static conditions. Bulb-to-bulb vacuum transfer may be accomplished with a standard 24/40 short path distillation apparatus. The reaction flask may be warmed slightly (40°C) with a water bath and the receiving flask is cooled in a liquid nitrogen bath. Vacuum is applied... 

Vacuum-filling apparatus to remove trapped air from the pores and for transferring mercury into the sample cell. 

A thin-walled glass tube containing acetaldehyde (0.5 mL) and (f-BuO)2 (3 pL) was degassed by two freeze -thaw cycles and frozen in liquid N2. To this was vacuum transferred [1.1. IJpropellane (6-7 mg). The tube was sealed under vacuum, warmed to rt, and photolyzed for 15 min in a Rayonet style photolysis apparatus. The tube was broken open and the excess acetaldehyde allowed to evaporate at rt, leaving solid material. The solid was chromatographed (silica gel, pentane/Et20 5 1) to give the product, yield 8.4 mg (52%). 

The solvent is removed in vacuo, yielding a sticky brown residue. The reaction vessel is taken into the drybox and the residue transferred to a short-path vacuum distillation apparatus (good results were obtained with an ACE model 9316 short-path still). The distillation still pot is heated slowly to 170°, and a clear, brown distillate comes over smoothly at a head temperature of 120-130° and a pressure of 10 3 torr. The apparatus is cooled to room temperature and taken into a drybox where the liquid U(OC2Hs)s is transferred to a tared bottle. Yield 12 g (60%). The yields obtained by the checker ranged 45-50%. 

Laser Flash Photolysis. A sample solution was prepared by vacuum-transfer techniques just before the measurements. Transient-absorption spectra and lifetimes of various intermediates were measured using the previously described apparatus (30). Excitation was with the fourth harmonic of a Nd YAG laser with a pulse width of ca. 30 ps. The solutin was vigorously stirred for 10 s between laser shots. 

C The reaction mixture is heated at 105-110°C for 72 h while the upper portion of the Carius tube is cooled with pressurized air. The pure product, 3,4,4-trifluoro-2,2-dioxo-3 (pentafluoro-A -sulfanyl)-l,2A -oxathi-etane, SF5CFCF2OSO2 (13.7 g, 47.6 mmol), is obtained, after vacuum transfer, by distillation in a Kontes (14/20), all-glass apparatus, at atmospheric pressure (bp 88°C), in 61.8% yield. The IR spectrum agrees with that reported previously. ... 

After 3 h of refluxing the solution is cooled and the pentane is removed under vacuum (14 torr). The residue is transferred to an appropriate vacuum distillation apparatus with a 25-mL vessel and an air cooler. The distillation under reduced pressure gives a colorless, pure product (10.96 g, 78%) with bp 30° at 0.001 torr and mp + 28° (DSC). 

A 100-ml. three-neck flask, equipped with a stirrer, a reflux condenser and a dropping funnel, isusedandl.68 g. of [N(CH3)3H]Cl is added to it. A solution consisting of 0.42 g. of LiBH4 in diethyl ether is slowly introduced from the dropping funnel. If vigorously stirred, the reaction proceeds at room temperature. When the generation of Hs diminishes, the contents are refluxed for another hour. All solvent is then distilled and the solid residue is transferred to a vacuum sublimation apparatus, where the BH3 N (0113)3 is sublimed in vacuum at 40°C and collected in a cooled receiver. The yield is 85%. 

After cooling, tip f is connected via a dry rubber tube to the vacuum-Ng (or Ar) system and broken off under Ns or Ar. The alkali metal at g serves as a barrier and traps any traces of water vapor which may be introduced. The tube can now be broken at h without endangering the product, and the mixture of rare earth metal + 3 alkali chloride at a may be poured into a transfer apparatus through which protective gas is flowing (for transfer apparatus see Part I, p. 75 ff., especially Fig. 54). 

While the oxidation is proceeding, set up a vacuum filtration apparatus using a 125-mL filter flask (should be clean and dry). Prepare a 1.27-cm Hirsch funnel to filter the reaction mixture (Technique 8, Section 8.3 and Figure 8.5 A). Place a moist (with water) piece of Whatman 2 filter paper into the Hirsch funnel. Weigh out 0.5 g of Celite (filter aid) in a beaker and transfer the solid to the Hirsch funnel. Using a bent spatula, adjust the Celite (filter aid) so that it covers the filter paper as evenly as possible. Weigh out 1 g of silica gel and add it on top of the filter aid to create as uniform a layer as possible. Turn on the aspirator or house vacuum system. 

Between the electrodes, current is carried partly by the silver ions and partly by the negatively charged nitrate ions. This leads to a situation which is analogous to space charge formation in a thermionic vacuum tube. Since the Ag ions are only partly responsible for the current in the electrolyte, they are not transported away from the anode immediately upon formation. There is, then, an accumulation of silver ions about the anode and a depletion of silver ions at the cathode. These phenomena can be observed in a Hittorf transference apparatus. Similar phenomena occur in mixed systems, for example, platinum electrodes in contact with sodium chloride solution. 

If a better NMR spectrum is required, a lithium chloride-free solution of the metallacycle must be prepared by either removing the THF by vacuum transfer (for apparatus and method see Protocol 2, step 7 and Fig. 5.7) and extracting the residue into toiuene, or by carrying out the metallacycle preparation In toiuene as soivent. in both these cases the lithium chioride is ailowed to settle out before removal of the sample for NMR spectroscopy. 

---