Chapter 20, Problem 1PP

Interpretation Introduction

Interpretation:

The procedure for separation of hexylamine from cyclohexane using dilute HCl, aqueous NaOH and diethyl ether is to be explained..

Concept Introduction:

Amines are organic derivatives of ammonia, in which hydrogen atoms are replaced by some organic compounds.

On the basis of hydrogen atoms being replaced from ammonia by the organic groups, amines are of three types: primary amines $\left({\text{RNH}}_2\right)$, secondary amines $\left({\text{R}}_2\text{NH}\right)$ and tertiary amines $\left({\text{R}}_3\text{N}\right)$. Amines are soluble in dilute acids.

Answer to Problem 1PP

Solution: Hexylamine is soluble in dilute acids but cyclohexane is not.

Explanation of Solution

Given information: A solution of cyclohexane and hexylamine is to be separated by dilute acid, aqueous NaOH and diethyl ether.

Amines with larger number of carbon atoms are insoluble in water but they are soluble in dilute acids. Thus, by dissolving amines in acids, they can be separated easily. Amines carry a lone pair, which forms a bond with the hydrogen atoms of acids while, cyclohexane being non-polar does not interact with acids. The interaction of amines with dilute acid is shown below:

The separated amines can be extracted from acid by dissolving in aqueous acid solution and then recovered by making the aqueous solution basic and extracting the amine in etheror ${\text{CH}}_2{\text{Cl}}_2$.

Conclusion

Hexylamine can be separated from cyclohexane by dissolving the amine derivative in dilute acid solution.