Question

Predict whether or not extraction will work for the separation of the following using water and dichloromethane as the two immiscible solvents. Give a reason for your prediction.

1. Paraffin wax from sodium chloride.

2. Decane from pentaerytritol, C(CH2Oh)4

3. Sodium benzoate from sodium chloride.

4. 1-Pentanol from 1-heanol.

Answer 1

Solvent extraction with dicholormethane and water works well for 1 and 2. It does not work for 3 and 4. This can be explained basing on the general principle “Like dissolves like” i.e polar substances dissolve in polar solvents and non-polar substances dissolve in non-polar solvents. Here, dichloromethane is non-polar and water is polar.

1. Paraffin wax from sodium chloride:

Here paraffin wax is non-polar and sodium chloride is polar. Therefore paraffin wax, dissolves only in dicholormethane but not in water. On the other hand sodium chloride dissolves only in water. So, separation is possible.

2. Decane from pentaerytritol, C(CH2Oh)4

Similarly, Decane(non-polar) dissolves in dicholormethane and pentaerytritol (polar) in water. So separation is possible in this case also.

3. Sodium benzoate from sodium chloride.

Both are ionic compounds (polar) and readily dissolve in water. Therefore it is not possible to separate by lquid-liquid extraction.

4. 1-Pentanol from 1-heanol(typo corrected to 1-hexanol).

In this case, the solubility difference between 1-pentanol and 1-hexanol is low. Both compounds have limited solubility in both water and dichloromethane as they compounds fall in between the polar and non-polar substances. Therefore, separation is very difficult to achieve.