Basic Characteristics of Aliphatic Amines

Amines are one of the most important topics in organic chemistry. Amines are derived when one or more than one hydrogen atom is replaced with an alkyl group. In this article, you will learn about Aliphatic Amines, their examples and the difference between aliphatic and aromatic amines. However, before learning about aliphatic amines, it is important to have proper knowledge about amines. 

Amines

Amines are functional groups that have nitrogen atoms with a single lone pair. They are structurally very similar to ammonia. Amines have nitrogen atoms along with lone pairs of electrons. These are derived from NH3, wherein one or more hydrogen atoms is replaced with an alkyl group. Therefore they are also called arylamines and alkylamines. Amines are classified into three types: primary amines, secondary amines and tertiary amines. 

Types of Amines

There are three types of amines differentiated based on the replacement of hydrogen atoms by ammonia molecules. They are:

Primary Amines

Here one hydrogen atom is replaced by an alkyl or aryl group.

Secondary Amines

Here two hydrogen atoms are replaced to form an amine.

Tertiary Amines

Here, organic substitutes replace all three hydrogen atoms. It could either be an aromatic group or an aryl group.

Chemical Properties of Aliphatic Amines

Amines have lone pairs of electrons. The ability of nitrogen to share these lone pairs of electrons with acid gives rise to the basic nature of amines. Amines, just like ammonia, are strong bases. They react with the mineral acids and hence form ammonium salts. They can be liberated from the ammonium salts when treated with a strong base such as NaOH. The basic nature of aliphatic amines can be depicted as tertiary amines > secondary amines > primary amines > ammonia. Hence they are a stronger base as compared to ammonia.

Aromatic and Aliphatic Amines

Aliphatic and Aromatic amines are different from each other based on their structure. Aliphatic amines are compounds where nitrogen is bonded with the alkyl group only. Aromatic amines, on the other hand, are those amine compounds where nitrogen is bonded with a minimum of one aryl group. The structural differences in these amines result in differences in other properties, like stability, acidity, reactivity, etc.

Aliphatic Amines: what are they?

In the case of Aliphatic Amines, the nitrogen is bonded with hydrogen atoms and one alkyl group. The total number of alkyl groups differs from one to three groups. These are categorised into: primary, secondary and tertiary amines depending on the number of alkyl groups bonded. 

In primary amines, one alkyl group is attached. Two alkyl groups are attached in secondary amines, and in tertiary amines, three are attached. 

Just like ammonia, they are weak bases. However, in comparison with ammonia, aliphatic amines are stronger bases. As the nitrogen atoms replace the alkyl groups, the basicity increases. Tertiary amines are the most basic as compared to primary and secondary amines. 

Aliphatic Amines are known as heterocyclic amines in situations where nitrogen is an atom in the ring. An example is Piperidine.

Aromatic amines: what are they?

In the case of aromatic amines, nitrogen is attached to one benzene ring. They can also be categorised into primary, secondary, and tertiary, depending on the total groups attached with the nitrogen atom. 

Aromatic Amines are also known as arylamines. Just like aliphatic amines, the three categories, i.e. primary, secondary and tertiary amines, can make intermolecular hydrogen bonds. Thus, the boiling point of tertiary amines is lower than primary amines and secondary amines.

Difference between aromatic and aliphatic amines

Here are some core differences between Aromatic and Aliphatic amines:

Based on structure

Alkylamines don’t have benzene rings that are attached to the nitrogen atom. Aromatic amines, on the other hand, have a minimum of one benzene ring attached to nitrogen atoms. Aliphatic amines have aromatic rings till nitrogen is attached to the carbon atoms.

Based on basicity

Aromatic amines are weaker bases as compared to aliphatic amines. This happens because of the stability of the cation, which is formed after ionisation. Aryl ammonium ions are less stable as compared to alkylammonium ions. Aromatic heterocyclic amines are weaker bases as compared to heterocyclic amines.

Piperidine is an example of aliphatic heterocyclic amines and pyrrole is an example of heterocyclic aromatic amines.

These were some basic differences between Aliphatic and Aromatic Amines.

Uses of Amines

There are multiple uses of amines in our daily lives. Some of the important uses of amines are listed here:

• Amines are used in the manufacturing of medicos, purification of water, manufacturing pesticides and insecticides. 

• Amines are used in making amino acids. Amino acids are known as building blocks of proteins in humans. Several vitamins are made by amines.

• Amines are used in manufacturing many painkillers like Demerol and morphine.

• Serotonin, which is an amine, acts as the primary neurotransmitter. 

Conclusion 

This was all about Aliphatic amines, their characteristics and the difference between Aliphatic and Aromatic Amines. Aliphatic and Aromatic amines are structurally very different from each other and hence their physical and chemical properties also differ. To understand the difference between Aromatic and Aliphatic Amines properly, you should read other basic topics as well, such as properties of amines, formation of amines and so on.