Teflon vacuum

The following steps are performed in an argon atmosphere glovebox. In a 50-mL round-bottom flask equipped with a Teflon magnetic stirbar, 2.03 g (14.7 mmol) of previously distilled and degassed 1,9-decadiene (9) (Aldrich) and 27.6 mg (3.61 x 10 2 mmol) of Schrock s catalyst (14) (400 1) are combined. In a matter of seconds, the catalyst is dissolved into the monomer and a vigorous evolution of ethylene is observed. The flask is sealed with a Teflon vacuum adapter and removed from the box. The polymerization vessel is immediately connected to the vacuum line, placed into an oil bath, and stirred at 30°C. Intermittent vacuum... 

OSHA versatile sampler (OVS) sorbent mbes (SKC, Inc., Cat. No. 226-30-16) Teflon vacuum pump (Analytichem International, N726.3FT.18)... 

A 0.056-g sample of AIBN (2,2 -azobisisobutyronitrile) is placed into a one-piece 100-mL flask (such as Chemglass AF-0522-02)t equipped with a Teflon vacuum stopcock and a magnetic stir bar, and the flask is evacuated at — 196°C. A 1.69-g (15.9 mmol) sample of B-vinylborazine (prepared by the procedure described above) is vacuum distilled into the flask. Three freeze-pump-thaw cycles are performed in order to remove any traces of oxygen. The stopcock is closed and the reaction flask is removed to a shielded hood where it is heated in an oil bath at 70°C for about 3 h, at which point the material is sufficiently viscous that the stir bar stops. Then 5 mL of benzene is condensed into the flask and the solution is heated at 70°C for another 9 h. Slow addition of the benzene solution into 40 mL of pentane under inert atmosphere affords the precipitation of 0.73 g (43.2% yield) of poly(B-vinyl-borazine). The polymer is filtered under nitrogen and dried in vacuo for about 5 min. 

With the Teflon vacuum valve of the solvent container closed (and the vacuum line under dynamic vacuum), the contents are thoroughly frozen by placing a dewar holding liquid nitrogen around the solvent storage container. The liquid nitrogen level should not reach the Teflon vacuum valve (it should be at least 1 in below the valve). 

Standard Teflon stopcocks cannot be used for any vacuum work. A completely different design from those discussed thus far is required for a Teflon vacuum stopcock. This design is shown in Fig. 3.22 and is called a rotary Teflon valve. It is called a valve instead of a stopcock because its operation and design is similar to those of a metal designed valve. 

A mixture of dry CsF [Kawecki Berylco] (2.361 g, 15.54 mmol) and [NFJfSbFs] (5.096 g, 15.64 mmol) is placed inside the dry box into trap I of the leak-checked and passivated (with CIF3 and dry HF ) Teflon FEP Monel metathesis apparatus shown in Fig. 2. The CsF is dried by fusion in a platinum crucible, immediately transferred to the dry box, cooled, and finely ground. The apparatus is attached to a metal Teflon vacuum system by two flexible corrugated Teflon tubes [Penntube Plastics], and the connections are vacuum leak-checked and passivated. The system is repeatedly exposed to anhydrous HF [Matheson], until the HF is colorless when frozen out at —196° in a Teflon U-trap of the vacuum system to avoid contamination of the product with any chlorine fluorides that may be adsorbed onto the walls of the metal vacuum system. Anhydrous HF (16.2 g, 810 mmol) is added to trap I, and the mixture is stirred magnetically for 1 hr at room temperature. The metathesis apparatus is cooled with powdered Dry Ice to — 78° for 1 hr and then inverted. The HF solution that contains the... 

SpeedVac concentrator (Thermo Fischer Scientific SPD131 DDA-230) fitted with ultralow temperature refiigerator (Thermo Fischer Scientific RVT4104-230) and oil-free Teflon vacuum pump (Thermo Fischer Scientific, OFP400-230). 

A 30 mL Pyrex Schlenk tube with a Teflon vacuum valve, a high vacuum line, a glove box, a 450-W medium-pressure Hg lamp, a temperature-controlled water bath, a 100 mL Schlenk tube, safety glasses, and a laboratory coat. 

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