Question

You are given a sample containing a hydrocarbon and an amine - both compounds are very insoluble in water and very soluble in diethyl ether. Describe how you could efficiently separate these two compounds using extraction methods; clearly explain why your procedure should give a good separation of the components (i.e., both compounds isolated in good yield and purity).

Answer 1

Amine is basic in nature because of NH2 group present in amine

Hydrocarbons are non polar and neutral

Basic compounds dissolve in acid solutions. Hence amine is soluble in HCl

Since basic NH2 gets convetred to ionic NH3+ in presence of acid , reaction is given by

R-NH2 + HCl (aq) --> RNH3+(aq)   + Cl-(aq)    where aq means aquos phase

Hence the mixture of hydrocarbon and amine are mixed in diethyl ether first to dissoolve both

Later solution transferred to seperatory funnel

Now aquoes HCl solution of equal volume as ether is added. Amines gets dissolved in aqueos layer having acid while hydrocarbon layers stays in ether layer

we get two layers in flask. Bottom one is aquoes layer conatining amines in NH3+ ) form and top layer is ether layer which has hydrocarbon.

Bottom layer is drained into another conatiner. Thus we seperate amines and hydrocarbons.

Amines seperated will be in NH3+ form , hence its treated with base to get back our amine form.

Hydrocarbons in ether solution is distiiled so that ether layer evaporates and we get pure hydrocarbon