Organic Chemistry - What Is Reflux?

We always see this reaction condition called “Reflux” when we study Organic Chemistry and their reactions.

I realised alot of students do not understand the true meaning of a reflux. This includes some of my JC2 and IB students who recently join our A-Level H2 Chemistry Tuition Classes.

So what really is Reflux?

Many organic chemical reactions take very long to complete, and in order to speed up these reactions, heat is applied. However, organic compounds are usually simple molecular structures with low boiling points. As such, most organic chemicals are quite volatile, and if heated they will evaporate and be lost. The solution to this problem is to heat the reaction mixture under reflux.

Diagram below shows the basic set-up of Refluxing:

(Source of diagram: Wikipedia)

Reflux involves heating the chemical reaction for a specific amount of time, while continually cooling the vapour produced back into liquid form, using a condenser. The vapours produced above the reaction continually undergo condensation, returning to the flask as a condensate.

The reactants for reflux experiments can be solid and liquid, or both liquids.

The condenser is always completely filled with water to ensure efficient cooling.

The vapours, which are given off from the liquid reaction mixture, change from gas phase back to liquid phase due to heat loss. This then causes the liquid mixture to fall back into the round bottom flask.

In this way, we can ensure that the chemical reaction involving organic compounds will give a higher yield of product.

You will see the use of reflux in many different topics in H2 Organic Chemistry. It is usually stated as “Heat with reflux” under the “Conditions” section.

Hope you find the information useful towards your learning of Advanced Organic Chemistry.

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends.

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