Evaporator System

Evaporation uses an all glass system. A good vacuum is needed to evaporate the TFA, thioanisole and other volatile liquids rapidly using a water bath temperature in the 30-35 ° C region (important). The time for evaporation must be as short as possible (lower yields may result from long evaporation times from poor pumping). Caution: a water aspirator can not be used. A Teflon pump (Aldrich, KNF pump) is the simplest apparatus otherwise the pump must be protected by a CaO trap to entrain the volatile and corrosive gases that are present in large quantity. Teflon pumps are available from Aldrich Chemical Company(800-558-9160) as KNF solid Teflon vacuum pumps.

To clean the evaporator, use a rotary-evaporator cleaner (Aldrich, Z11,573-8) shown below.

To use, fill the tube with solvent and attach to the evaporator by means of the ground glass joint. Put your thumb over the other end of the tube and turn on the vacuum to the evaporator. When the vacuum increases, release your thumb and the solvent will "splash" through the evaporator rinsing hard to reach parts of the evaporator. Repeat several times until the evaporator is clean. This is an efficient method for cleaning any rotary evaporator. After evaporating the TFA and other volatile liquids, rinse the evaporator with water several times using the rotary evaporator cleaner and then substitute ethanol for the water and the ethanol will dry the apparatus suitably for the next TMS Br cleavage.

Rotary evaporator cleaner. A substitute piece of equipment is a distillation take off adapter with ground glass joints at both ends.

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Last modified:2/12/2005