Question

In lab we did a liquid-liquid extraction using a separatory funnel - but i don't really understand what was happening ( i just followed directions given) - now my lab report asks me to describe

1. the concept of liquid liquid extraction and how it works

2. Describe how adjusting the pH of the aqueous phase as a means of altering solublity properties of compounds is used in extractions??

can anyone help me understand these two questions above.

Answer 1

1.

Principle of liquid liquid extraction relies on the immiscibility of two liquid componenets, mainly organic layer and aqueous layer.Generally, organic compounds are soluble in organic solvents like ethyl acetate and on the other hand organic/inroganic salts, compounds are soluble in water layer.

Taking advantage of these differences, organic compounds are extracted after the reaction using a suitable organic solvent which is immiscible with water. Depending on the density of the organic solvent it may be in the top layer or bottom layer. For example ether is lighter than water, stays on the upper layer but dichloromethane, which is havier than water, stays in the lower layer.

2.

Organic compounds can be acidic, basic and neutral. If a separation is reuired from a mixture of compounds containing any two or all three types of organic compounds then the pH can play an important role. For example, if Benzoic acid has to be separated from a mixture of aniline and xylene, then by treating with NaOH its salt C6H5COONa is formed whcih is soluble in aqueous solution and can be separated from other two components.

Now, aniline and xyline, will be in organic layer which can be traeted 6M HCl resulting C6H5NH3Cl, a salt soluble in aqueous medium and can be separated by separating layers.

Xyline will be in organic layers.