Question

\[C_3H_9N\] cannot represent:
A.\[{1^0}\] amine
B.\[{2^0}\] amine
C.\[{3^0}\] amine
D.quaternary salt

Answer 1

Hint: We have the compound with the molecular formula \[{C_3}{H_9}N\]. We can use the basics of isomers here. Make the isomers of a compound with the molecular formula \[{C_3}{H_9}N\]. Then classify them as primary, secondary, and tertiary amines.

Complete step by step answer:
We will try to draw some isomers of a compound with the molecular formula \[{C_3}{H_9}N\]. We will consider and understand all the options one by one. So let’s start.
We can write the structure of the compound with molecular formula \[{C_3}{H_9}N\] as,

The above structure is a primary \[{1^0}\] amine. As the nitrogen atom is surrounded by a single carbon or chain. So we can represent \[{C_3}{H_9}N\] as \[{1^0}\] amine.
Now consider another structure with the molecular formula \[{C_3}{H_9}N\] which is represented as,

The above structure is \[{2^0}\] amine. Here the nitrogen atom is surrounded by two carbon atoms. So we can represent \[{C_3}{H_9}N\] as \[{2^0}\] amine.
Now we will consider another structural isomer of molecular formula \[{C_3}{H_9}N\] which is represented as,

The above structure is a \[{3^0}\] amine. In the structure, we can observe that the nitrogen atom is surrounded by three carbon atoms therefore it is termed as \[{3^0}\] amine. So we can represent \[{C_3}{H_9}N\] as \[{3^0}\] amine.
Now the last option is quaternary salt. This salt is represented as \[{R_4}\mathop N\limits^ + \mathop Z\limits^ - \] where \[{R_4}\] represents the alkyl group with \[4\] carbon atoms. But in the compound with the molecular formula, \[{C_3}{H_9}N\] we have \[3\] carbon atoms. So we cannot represent \[{C_3}{H_9}N\] it as quaternary salt.

Therefore, the correct option is (D).

Note:
\[{R_4}\mathop N\limits^ + \mathop Z\limits^ - \] is the quaternary ammonium halide. It is formed when ammonia accepts one proton to form an ammonium ion and the tertiary amine accepts an alkyl group to form a quaternary ammonium ion.
Primary, secondary and tertiary amines are represented as \[{1^0},{2^0},{3^0}\] amine respectively.