Question

Primary and secondary amines are distinguished by:

Answer 1

Primary amines are those in which the nitrogen atom is attached with two hydrogen atoms and secondary amines are those in which the nitrogen atoms are attached with one hydrogen atom. Nitrous acid is used to distinguish the amines.

Complete answer:
Most of the organic compounds look similar so, it has to be identified and distinguished. The given compounds in the question are primary amines and secondary amines. As amines are those compounds in which the functional group $-N{{H}_{2}}$ is attached with a carbon chain.
Primary amines are those in which the nitrogen atom is attached with two hydrogen atoms and secondary amines are those in which the nitrogen atoms are attached with one hydrogen atom. The general formula of primary amine is $R-N{{H}_{2}}$ and the general formula of secondary amine is ${{R}_{2}}-NH$.
So, these can be distinguished by nitrous acid whose formula is $HN{{O}_{2}}$.
When the primary amine is treated with nitrous acid then there is the formation of alcohols as the amine group in the carbon chain is replaced with the hydroxyl group. The general reaction of a primary amine with nitrous acid is given below:
$R-N{{H}_{2}}\xrightarrow{HN{{O}_{2}}}R-OH$
But when the nitrous acid is treated with secondary amine then there is the formation of N-nitroso derivatives. The general reaction of nitrous acid with secondary amines is given below:
${{R}_{2}}-NH\xrightarrow{HN{{O}_{2}}}{{R}_{2}}-N-NO$

Note:
When the primary amine is treated with nitrous acid then the formed alcohol will be also primary. If we want to distinguish between primary, secondary, and tertiary amines then we use the hinsberg’s test.