$ - H\mathop { - N}\limits_{\mathop |\limits_H } - \mathop C\limits_{\mathop |\limits_R } = O - $$ - H - \mathop N\limits_{\mathop |\limits_H } - \mathop C\limits_{\mathop |\limits_R } = O - $$ - H - \mathop N\limits_{\mathop |\limits_H } - \mathop C\limits_{\mathop |\limits_R } = O - $

Due to intermolecular hydrogen bonding they have high boiling point than amine and amongst amide the order of Boiling point are

Primary $>$ Sec $>$ Tertiary

This is because of alkyl group by which the carbonyl oxygen do not form the hydrogen bond (other molecule) so primary amide have high boiling point and Tertiary amides does not have to form bond with $O$ of other amide and have least $B.P$