Alkyl Amines

Amines are compounds and functional groups that consist of a basic nitrogen atom and a lone pair and are generally derived, either in principle or in practice, from ammonia (NH3). These are considered an essential class of compounds and are usually obtained by replacing one or more hydrogen atoms of the ammonia molecule with the alkyl groups.

What are Alkyl Amines?

Amine is a compound derived from ammonia (NH3). They are essentially classified as functional groups for organic nitrogen compounds, consisting of large amounts of the nitrogen atom with a lone pair. Hydrogen atoms are replaced by an aryl or alkyl group in amines.

Many of the naturally occurring amines includes alkaloids found in different plants, such as catecholamine neurotransmitters, like epinephrine, dopamine, and norepinephrine, as well as a certain chemical mediator, histamine. It also exists in various animal tissues. Some common examples of amines are amino acids, aniline, and trimethylamine.

Furthermore, inorganic ammonia compounds like monochloramine (NCIH2) are also called amines. Amines occur naturally in vitamins, proteins, hormones, and many other forms. They can also be created through different synthetic processes. Alkyl amines are tetrahedral nitrogen centres. Here, the angle of C-N-C and C-N-H is 109°.

Properties of Amines

• Low aliphatic amines with a fishy smell are gaseous.
• Primary amines, at room temperature, are liquid in form and tend to contain anywhere between three and four carbon atoms, while the higher amines are solid in form.
• Usually, aniline and other forms of arylamines are colourless. But if they are stored in the open, they get painted, i.e., they become colourful due to atmospheric oxidation. 
• Lower forms of aliphatic amines are known for making hydrogen bonds with water molecules, making them soluble in water. 
• The boiling point of amines is at 48.6°C > 37.0°C > 3.5°C.
• Due to hydrogen bonding between nitrogen and hydrogen of another atom, the primary and secondary amines are involved in the intermolecular interaction.
• This intermolecular association is even more visible in primary amines than secondary amines due to the availability of two hydrogen atoms.

Types of Amines

Amines can be broadly categorised based on their nature. However, mainly they are classified into two types—aliphatic amines (as they have only hydrogen and alkyl substituents) and aromatic amines (because nitrogen is connected with an aromatic ring). Based on this, it can be said that the amines are further categorised into primary, secondary, tertiary, and quaternary amines.

Primary amines (1° Amines) are formed due to the substitution of one hydrogen atom in ammonia by an alkyl or aromatic group. It is mainly found in amino acids and methylamine. 

Secondary amines (2° Amines) have two organic substituents: alkyl or aryl, or even both.

Tertiary amines (3° Amines) are the ones in which the nitrogen contains more than three organic substituents.

The nitrogen in quaternary amines (4° Amines) consists of four organic substituents and a positive charge.

Preparation of Amines and Reactions

Amines can be prepared using different methods and techniques. However, they are mostly divided into two methods—reaction of ammonia with organic compounds, and chemical reduction in which the hydrogen atom replaces the oxygen atom in the molecule.

One process of amines preparation is alkylation. This method is used in industries where alcohols are alkyd from ammonia (ROH + NH3 → RNH2 + H2O).

Acylation is another process of preparing amines. It consists of a reaction between chlorine, anhydride, and ester. It is regarded as a type of nucleophilic substitution reaction. Here, the hydrogen atoms are substituted by an acyl group.

Conclusion

Amines are compounds and functional groups consisting of a basic nitrogen atom with a lone pair. They are generally derived, either in principle or in practice, from ammonia (NH3). Many naturally occurring amines include the likes of alkaloids found in different plants, such as catecholamine neurotransmitters, like epinephrine, dopamine, and norepinephrine, as well as a certain chemical mediator, histamine.

Amines can largely be categorised based on their nature. However, mostly they are classified into two types—aliphatic amines and aromatic amines. They can be prepared using different methods and techniques, such as the reaction of ammonia with organic compounds, and chemical reduction in which the hydrogen atom replaces the oxygen atom in the molecule.