Oil bubblers

The entire reaction sequence is performed under an argon atmosphere which is connected by a T-tube to the assembly and an oil bubbler, and is operated at a moderate flow-rate throughout the synthesis. 

The apparatus consists of a 2-1., three-necked, round-bottomed flask equipped with a mechanical stirrer, a pressure-equalized dropping funnel through which dry nitrogen can be added, and a reflux condenser, and is to be maintained at 0°. The outlet tube on the reflux condenser leads to a large U-tube trap, fitted with stopcocks on both sides, and immersed in a Dry Ice-isopropyl alcohol bath. The U-trap vents to a mineral oil bubbler. (See Fig. 17.) Sodium fluoride, 454 g. (10.8 mols) is added to the flask followed by approximately 1200 ml. of tetramethylene sulfone. The system is then flushed thor-... 

A. 1-Bromo-1-phgnylthioethene. A 300-mL, two-necked, round-bottomed flask is fitted with a magnetic stirring bar, pressure-equalizing dropping funnel, and a reflux condenser to which a nitrogen inlet tube and an oil bubbler are attached, and flushed with nitrogen (Note 1). In the flask are placed 13.6 g (100 mmol) of phenyl vinyl sulfide (Note 2) and 80 mL of ether (Note 3), which are then cooled to ca. -78°C with a dry ice-methanol bath. Bromine (16.0 g. 100 mmol) is added dropwise over 30 min to the... 

The apparatus is flame-dried under a stream of dry nitrogen or argon. Later a slight positive nitrogen pressure is maintained with an oil bubbler throughout the reaction. 

A. (Tn fluoromethyl)trimethylsilane. A 2-L, three-necked flask is fitted with an efficient, over-head, sealed mechanical stirrer, a cold-finger condenser (30-cm in length and 8-cm in diameter) and a rubber septum (Note 1). The top outlet of the condenser is attached to an oil bubbler. The flask is flushed with dry nitrogen and charged with 118.8 g (1.09 mol) of chlorotrlmethylsilane (Note 2) in 100 mL of... 

A. (S)-Phenylalanol. A dry, 3-L, three-necked flask is equipped with a mechanical stirrer and a reflux condenser connected to a mineral oil bubbler. The flask Is loaded with 165 g (1.00 mol) of (S)-phenylalanlne (Note 1), then equipped with a 250-mL pressure-equalized addition funnel capped with a rubber septum through which is Inserted a nitrogen-inlet needle. The flask Is swept with nitrogen and filled with 500 id. of anhydrous tetrahydrofuran, and the addition funnel is charged with 123 mL (1,00 mol) of freshly distilled boron trifluoride etherate via cannula (Note 2). The boron trifluoride etherate Is added dropwlse to the phenylalanine slurry over a 30-m1n period with stirring, and the mixture is heated at reflux for 2 hr, resulting in a... 

A. N-Benzylideneheneeneaulfonam-fAe. A 3-L, one-necked, round-bottomed flask is equipped with a mechanical stirrer (Note 1), Dean-Stark water separator (Note 2), double-walled condenser attached to an argon gas inlet and outlet needle connectors through a mineral oil bubbler. Into the flask are... 

An apparatus consisting of a 1000-mL, three-necked flask fitted with a mechanical stirrer and reflux condenser is flushed with nitrogen for several minutes. A positive nitrogen pressure is maintained thereafter by a mineral oil bubbler connected to a T-tube in the gas line between the nitrogen cylinder and the... 

Larger scale preparations (up to 0.100 mole) have been carried out on the bench top (in the hood ) under inert atmosphere conditions (a slow nitrogen purge through a oil bubbler), using the appropriate scale-up in reactant and solvent quantities. The reaction is complete in about 72 hours. The bulk of the solvent can be removed by evaporation at or below room temperature under reduced pressure on the bench top [heating should be avoided because it leads to significant product decomposition and the formation of HMn(CO)5 and Mn2(CO)io impurities]. The final purification of the product should be accomplished on the vacuum line. 

The methane generated is vented by passage through the oil bubbler. 

Fig. 2. First distillation assembly (A) 3-L reaction flask, (B) 15-in Vigreaux column, (C) 24/40 distillation head with 150 °C thermometer, (D) water-cooled condenser, (E) to glass tee, which is also connected to an N2 source and a mineral oil bubbler, (F) 200-mL Schlenk receiver flask.

Caution. Owing to the scale of the reaction, care must be exercised regarding free flow of gas through the apparatus, especially the collection of product in the cold trap. Mineral oil bubblers are used to monitor gas flow and ensure that the product collecting in the cold trap has not plugged the flow. 

---