Amine vs Amide
 

Amines and amides are both nitrogenous organic compounds. Although they sound similar, their structure and properties are very different.

Amine

Amines can be considered as organic derivatives of ammonia. Amines have nitrogen bonded to a carbon. Amines can be classified as primary, secondary and tertiary amines. This classification is based on the number of organic groups that are attached to the nitrogen atom. Hence, primary amine has one R group attached to nitrogen; secondary amines have two R groups, and tertiary amines have three R groups. Normally, in nomenclature, primary amines are named as alkylamines. There are aryl amines like aniline, and there are heterocyclic amines. Important heterocyclic amines have common names like pyrrole, pyrazole, imidazole, indole, etc. Amines have a trigonal bipyramidal shape around the nitrogen atom. The C-N-C bond angle of trimethyl amine is 108.7, which is close to the H-C-H bond angle of methane. Thus, the nitrogen atom of amine is considered to be sp3 hybridized. So the unshared electron pair in nitrogen is also in a sp3 hybridized orbital. This unshared electron pair is mostly involved in the reactions of amines. Amines are moderately polar. Their boiling points are higher than the corresponding alkanes, due to the ability of making polar interactions. But their boiling points are lower than the corresponding alcohols. Primary and secondary amine molecules can form strong hydrogen bonds to each other and with water. But tertiary amine molecules can only form hydrogen bonds to water or any other hydroxylic solvents (cannot form hydrogen bonds between themselves). Therefore, tertiary amines have a lower boiling point than the primary or secondary amine molecules. Amines are relatively weak bases. Although they are stronger bases than water, compared to alkoxide ions or hydroxide ions, they are far weaker. When amines act as bases and react with acids, they form aminium salts, which are positively charged. Amines can also form quaternary ammonium salts when the nitrogen is attached to four groups and thus become positively charged.

Amide

Amide is a derivative of carboxylic acid. Therefore, they have a carbonyl carbon with an attached R group. And there is a –NH2 group which is directly attached to the carbonyl carbon. Amides with no substituent on nitrogen are named by adding –amide to the end of the common name of the relevant acid. If there are alkyl groups attached to the nitrogen atom, then, those groups are named as substituents. Amides with no or one substituents on the nitrogen are capable of forming hydrogen bond to each other; thus, melting points and boiling points of such amides are higher. Molecules with N, N- disubstituted amides can’t form hydrogen bonds with each other, and consequently have lower melting points and boiling points.

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