Chemical Differences. (see the flow chart at page 20) A derivative is synthesised and separated from the other components by precipitation or extraction.* The usual type of derivative is formation of a salt, e.g., if given an acidic/neutral mixture insoluble in water, the acidic component can be extracted into aqueous basic solution. Similarly, a phenol/neutral mixture can be treated in the same way as most phenols are sufficiently acidic to be extracted into aqueous sodium hydroxide. For a basic/ neutral mixture, extraction into aqueous acid will affect a separation. For example, a mixture of benzoic acid benzophenone can be separated by aqueous NaOH/ ether; a mixture of aniline and chlorobenzene can be separated by aqueous HCl/ether. The separated components are then recovered and purified. *Caution: It is wise to try out on a small scale first. Water soluble organic compounds may be troublesome, so it is best to avoid too much of aqueous reagents. A mixture of a phenol and a ketone with α-hydrogens would both dissolve in NaOH. Solution of the phenol may be affected with very dilute NaOH and done rapidly to avoid decomposition of the carbonyl compound. Some amines form salts which may not dissolve readily in H2O, a different acid may be used.
