Practical Organic Chemistry
4.0 Methods of Separation of Mono-functional Organic Compounds from Binary Mixtures
4.0 Methods of Separation of Mono-functional Organic Compounds from Binary Mixtures
Separation Based on Differences in the Chemical Properties of the Compounds
1. Toluene and Aniline: A mixture of toluene may be separated by extraction with dilute $HCl;$ the aniline passes into the aqueous layer in the form of the salt aniline hydrochloride and may be recovered by neutralization.
2. Phenol and Toluene: They can be separated by treatment with dil. $NaOH$
3. Dibutyl Ether and Chlorobenzene: Concentrated ${H_2}S{O_4}$ dissolves only the dibutyl ether and it may be recovered from solution by dilution with water.
The above examples are simple applications of the fact that the various components fall into different solubility groups.
4. Phenols and any compound containing group (e.g. o-cresol from benzoic acid): Phenols may be separated from acids by a dilute solution of $NaHC{O_3};$ the weakly acidic phenols (and also enols) are not converted into salts by this reagent and removed by ether extraction; the acids pass into solution as the sodium salts and may be recovered after acidification.
5. Separation of mixture of amines: Mixture of primary, secondary and tertiary amines can usually be separated by Hinsberg method. The mixture of amines is treated with $NaOH$ solution and toluene-p-sulphonyl chloride is warmed in a water bath and finally acidified with dil. $HCl,$ the sulphonamides of primary and secondary amines are precipitated. The solid is filtered and washed with a little cold water, the tertiary amine will be present in the filtrate. The solid is then treated with alkali again. The sulphonamide from the primary amine goes into solution and the precipitate of the sulphonamide of the secondary amine is filtered off. The filtrate is acidified with dil. $HCl$ to precipitate the derivative of the primary amine.
6. Aldehydes and Ketones from other liquid hydrocarbons and other neutral liquid compound (e.g. ethanal and ethanol): The mixture is shaken with a solution of $NaHC{O_3};$ the carbonyl compound forms a solid bisulphite compound which is filtered off and decomposed with dil. acid in order to recover the aldehyde or ketone.
