last updated 12/29/2014

This basic reaction setup e.g. for Grignard reaction consists of a three-necked flask, a addition funnel (on the right), a reflux condenser and a gas adapter (for air sensitive reactions). Here are a few pointers for the setup:

1. The entire setup is clamped at the center neck of the three-necked flask. It holds the weight of the entire setup and you can remove the heating source without the flask dropping on the bench. For larger (heavier) setups it is highly advisable to support the setup by clamping the condenser in the middle as well to prevent tipping over.

2.The flask should not be more than half filled to allow enough room for expansion and boiling. One has to also keep in mind that the volume can significantly increase if a solution is added from the addition funnel. Thus, the size of the flask used depends on the total volume in the end!

3. The reflux condenser is usually placed in the center. This makes it easier to balance the entrire setup. The inlet of the water is connected to the lower end of the condenser and the outlet at the upper end independent if the condenser is used for reflux or distillation mode. This way, a low flow rate of the water will be sufficient for cooling because the outer jacket of the condenser will fill up with water first before it reaches the outlet. The gas adapter has to be placed on top of the reflux condenser and is connected to the Schlenk line (or a bubbler).

4. One has to make sure that the stopcock of the addition funnel does not leak. It is pretty frustrating to have to start over because one discovers that the stopcock leaks after the glassware was prepared (dried with the heat gun).

5. The green plastic clips serve the purpose to hold the different pieces of glassware together. They give some more security, but they are not able to prevent the setup from being disassembled if you build up a significant overpressure.

6. If a system is heated, an 'overpressure valve' has to be in the setup. It doesn't matter what is being heated, but the media will always will expand (more or less). This will ultimatively build up a significant pressure, which can cause heavy explosions. In many cases, the setup is connected to the inert gas part of the Schlenk line. However, the appropriate plug has to be opened before the setup is heated.

7. Lastly, a spin bar has to be added to the flask to mix the solution during the reaction/reflux. Why?