Question

Why do primary amines have higher boiling point than tertiary amines?

Answer 1

Hint: Amine is a functional group containing a nitrogen atom and one lone pair. Based on the number of carbon atoms binding to nitrogen atoms, these are classified as primary,secondary and tertiary. Amines are generally derivatives of ammonia which contain three hydrogen atoms. Based on the number of hydrogen bonds, the boiling point varies.

Complete answer:
In organic chemistry, there are many trends which keep on changing according to their chemical nature. One such trend is the boiling points of amines. Let us see how they differ. Amine contains three hydrogen bonds and when one of these hydrogen bonds is replaced by any aromatic or alkyl group, that will give rise to primary amine. In the same manner, two hydrogen bonds are replaced in secondary amine and three hydrogen bonds are replaced in case of tertiary amine. There is a direct relation between the hydrogen bonding and boiling point. More the number of hydrogen bonds, more will be the energy to break the bond between them and more is the boiling point. So, among the amines it is the primary amine where more hydrogen bonds are present and hence more is the boiling point. The order of boiling point in amines is as follows: primary amine,secondary amine and tertiary amine.

Note:
Hydrogen bonding is said to be one of the strongest attractions. The bond is formed between a positively charged hydrogen atom and any other negatively charged atom like N,O etc. There are two types of hydrogen bondings which are intermolecular hydrogen bonding and intramolecular bonding. It is said to be the strongest, but weaker than a covalent and ionic bond.