When a reaction has finished, the desired product should be present in the reaction flask. However, there are likely to be many other things also present – solvents, unreacted starting materials, by‑products etc. In order to isolate the product with a reasonable level of purity, these other things must be removed, and the general procedures for isolating different types of product are called “work-up”. General procedures for work-up can vary enormously, depending on the nature of the product. For example, if the product crystallises from the reaction mixture, the work-up may simply consist of filtering the mixture to recover the solid product, and then recrystallising the product. If the product is a liquid, it may be possible to purify it conveniently by distillation. However, in many cases, the reaction mixture will consist of a mixture of organic and aqueous material, and the work-up will involve more steps, such as extraction and washes with various solutions. These operations are often called “aqueous work-up”, and are detailed in this section.

Extractions and washes use a piece of equipment called a separatory funnel. Careful and efficient use of the separatory funnel is crucial to a successful work-up, so the general use of the separatory funnel will be discussed first. This is followed by a section on extraction and washing, essentially the same technique, which uses differences in solubility to separate components. This is followed by a section on chemically-active extraction (“acid-base work-up”), which also uses differences in solubility, but also makes chemical changes to the molecules to effect their separation. The last section focuses on how to deal with problems that arise with extractions.