Question

Among ${{(C{{H}_{3}})}_{3}}N$ and $C{{H}_{3}}N{{H}_{2}}$ , amine with __________ methyl groups attached has the higher boiling point.

Answer 1

Hint: An amine is an organic compound that contains nitrogen atoms with a lone pair. It is a derivative of ammonia, in which one or more hydrogen is replaced by a substituent group. Amines are classified according to the number of substituent groups attached with nitrogen. It can be aliphatic amine or aromatic amine.

Complete step by step solution:
-Amines are categorized on the basis of the number of carbon atoms adjacent to the atom of nitrogen. It can be primary amine, secondary amine and tertiary amine.
-Primary amine – When one alkyl group replaces one of the three hydrogen atoms in ammonia, it results in the formation of primary amines.
-Secondary amine – When two alkyl groups replace two of the three hydrogen atoms in ammonia, it is known as secondary amine.
-Tertiary amine – When three alkyl groups replace all the three hydrogen atoms in ammonia, it is known as tertiary amine.
-In this question, ${{(C{{H}_{3}})}_{3}}N$ is a tertiary amine having three alkyl groups, whereas $C{{H}_{3}}N{{H}_{2}}$ is a primary amine, having only one alkyl group.
-Primary amine can form intermolecular hydrogen bonding because of the presence of two hydrogen atoms. In tertiary amine, there is no hydrogen atom present, so there will be no intermolecular hydrogen bonding. In primary amine, the presence of hydrogen bonding will result in the higher boiling point than the tertiary amine as it does not contain any intermolecular hydrogen bonding. Therefore, the boiling point of $C{{H}_{3}}N{{H}_{2}}$ is greater than that of ${{(C{{H}_{3}})}_{3}}N$ .
So here, $C{{H}_{3}}N{{H}_{2}}$ is the amine with one methyl group attached and has the higher boiling point.

Note:
-Amines are basic in nature because of the presence of lone pairs on the nitrogen atom.
-In amines, hydrogen bonds are formed between lone pairs on electronegative nitrogen atoms and slightly positive hydrogen atoms in a molecule.