Question

Primary, secondary, tertiary amines can be separated by the following except:

• A. Fractional distillation
• B. Fractional method using diethyl oxalate
• C. Hinsberg's method using $C_6{H}_5{SO}_{2}Cl$
• D. Selective crystallisation

Answer 1

The correct option is D Selective crystallisation

Separation of $1^o,2^o$ and $3^o$ amines:

$1^o,2^o$ and $3^o$ amines + $R_{4}NX\stackrel{distillation}{\to }$ Mixture of $1^o,2^o,3^o$ amine

Mixture of $1^o,2^o,3^o$ amine can be separated by following methods.

(i) Fractional distillation: The mixture of amines may be fractional distillation because their boiling points are quite different. It is used in industry.

(ii) Hinsberg method: In this method mixture of amines is seperated by using benzene sulphonyl chloride (Hinsberg's reagent).

$C_6{H}_{5}S{O}_{2}Cl+1^{o}amine\to Product\stackrel{KOH}{\to }dissolve$

$C_6{H}_{5}S{O}_{2}Cl+2^{o}amine\to Product\stackrel{KOH}{\to }insoluble$

$3^o$ amine does not react with benzene sulphonyl chloride.

(iii) Hofman method: In this method mixture of amines is separated by using ethyl oxalate.

$1^o$ amine + ethyl oxalate $\to$ solid product

$2^o$ amine + ethyl oxalate $\to$ liquid product

$3^o$ amine + ethyl oxalate $\to$ No reaction