Question

Ethyl amine on heating with \[C{S_2}\]​ in presence of $HgC{l_2}$ forms
(A) ${C_2}{H_5}NCS$
(B) ${\left( {{C_2}{H_5}} \right)_2}S$
(C) ${\left( {{C_2}{H_5}} \right)_2}CS$
(D) ${C_2}{H_5}{\left( {CS} \right)_2}$

Answer 1

Hint: Hofmann mustard oil reaction is what is happening in this situation. If we carefully examine the reaction taking place here, we will see that alkyl isothiocyanate is the provided result, with chemical formula ${C_2}{H_5}NCS$ . This is the product obtained by the Hofmann mustard oil reaction.

Complete Step by Step Solution:
The Hofmann mustard oil reaction is a chemical process that produces isothiocyanates when primary amines are heated with alcoholic carbon disulfide \[\left( {C{S_2}} \right)\] and excess mercury chloride $HgC{l_2}$ . The reaction produces a strong odour that is brought on by these isothiocyanates. This odour is reminiscent of mustard oil.
The test to distinguish between primary, secondary and tertiary amines is the Hofmann mustard oil reaction.

When primary amines are treated with carbon disulfide and then heated with too much mercury chloride, isothiocyanates are produced that give off a strong odour akin to that of mustard oil. Dithiocarbamic acids are created when secondary amines and carbon disulfide interact. However, it does not interact with the mercuric chloride in the following step. None of the reagents react with tertiary amines \[\left( {C{S_2}\,\& \,HgC{l_2}} \right)\] .
We notice that a dark, insoluble precipitate forms during the process. Actually, during the process, \[HgS\] is produced as this insoluble precipitate.
Hence, option A. is the answer.

Note: The test used to differentiate between primary, secondary, and tertiary amines is this one. It's crucial to keep in mind that aromatic primary amines can pass this test as well. As a result, this test is unable to differentiate between aromatic and aliphatic amines.