Question

Ethyl dimethyl amine is:
A. tertiary amine
B. primary amine
C. secondary amine
D. None

Answer 1

Hint: Try to think about the nomenclature of the amines. The nomenclature of alkyl amines depends on the fact that how Many alkyl groups or hydrogen is present/ attached with the nitrogen of the amine.

Complete answer:
In order to answer the question, we need to learn about the nomenclature of amines and what they actually are. Amines are organic derivatives of ammonia in which one or more than one hydrogen atom is replaced by other atoms or groups of atoms. They are classified as primary amines ($RN{{H}_{2}}/{{1}^{0}}$), secondary amines (${{R}_{2}}NH/{{2}^{0}}$) or tertiary amines (${{R}_{3}}N/{{3}^{0}}$)depending upon one, two or all the three hydrogen atoms of ammonia displaced by alkyl groups (R). As an 'N' atom in$N{{H}_{3}}$, the molecule is $s{{p}^{3}}$hybridised and tetrahedral in geometry. Similarly 'N' atom in all amines is also $s{{p}^{3}}$hybridised which has tetrahedral geometry but their shape is pyramidal. Out of four hybrid orbitals of nitrogen three orbitals overlap with hydrogen or carbon atoms of the alkyl group depending upon the composition of amines, whereas the fourth hybrid orbital contains lone pair of electrons. Repulsion between lone pair and bond pair electrons suppresses the bond angle which becomes lesser than ${{109.5}^{0}}$. The structures are:

The structure of ethyl dimethyl amine is:

There is no hydrogen atom attached to the nitrogen, instead three alkyl groups are attached.

Hence, it is a tertiary amine. So, our correct answer would be option A.

NOTE: Ethyl dimethyl amine is used for sand core production, as a catalyst in the foundries. In room temperature, it is generally a liquid, however it is very volatile. It has a very low melting point of $-{{140}^{0}}C$.