6.1 Reflux

This lesson will give you a basic idea of how to set up a simple apparatus to heat and stir reactions. This apparatus will form the basis of many reactions and purification techniques you will perform during your degree.

What is a Reflux Apparatus?

One of the first synthetic techniques you will learn to set-up and use is a refluxThe process of evaporating a solvent and condensing it again. Running a reaction at reflux means to run a reaction at the boiling point of the solvent. apparatus. A reflux allows you to stir and heat any mixture without losing the solvent. The condenser is placed vertically above the flask the reaction is happening in to allow any evaporated liquid to condense and fall back into the reaction mixture.

The point of a refluxing solution is to heat a solution in a controlled manner at constant temperature. The reaction mixture always stays at, or close to, the boiling point of the solvent as any excess heat is lost in the evaporation and condensation process. This is very useful for reactions that need to be carried out for long periods of time. It also means any solvent vapours are contained within the apparatus which could otherwise pose fire hazards or be harmful to health.