Amines

Classification of Amines

You have heard of Ammonia. Haven’t you? But, it is not the only nitrogen product that is popular. There are so many other products of ammonia that are derived by altering the hydrogen atoms. We give them names like Primary amine or Secondary amine etc. In this chapter, we will look at the classification of amines in details. We will also have a brief look at the nomenclature of the classification of amines.

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What are Amines?

Amines are the organic compounds derived from ammonia (NH3). They are derived by replacing its one or more hydrogen atoms by alkyl or aryl group. For example:

CH3NH2 C2H5NH2 C6H5NH2
Methyl Amine Ethyl Amine Aniline

Classification of Amines

On the basis of the number of hydrogen atoms replaced in NH3 molecule, amines are categorized into three types:

1° or the Primary Amines

In 1° amine, one hydrogen atom of NHis replaced by an alkyl or aryl group. For example:

  • CH3NH2
  • Methyl Amine

2° or the Secondary Amines

In 2° amine, two hydrogen atoms of NHare replaced by alkyl or aryl groups. For example: CH3NHCHor Dimethyl Amine

3° or Tertiary Amines

In tertiary amine, all the three hydrogen atoms of NHare replaced by alkyl or aryl groups. For example:

classification of amines

Nomenclature of Amines

  • In the common naming system, we name aliphatic amines by prefixing an alkyl group to a mine, i.e. alkylamine. For example:

Classification of Amines

  • Secondary and tertiary amines, having two or more similar groups are named by adding prefix ‘di’ or ‘tri’ before the name of the alkyl group. For example:

Classification of Amines

  • Aromatic amines are named as derivatives of the parent member, aniline (C6H5NH2). For example:

Classification of Amines

Solved Examples for You

Question: Write a detailed note on the nomenclature of amines.

Answer: In organic chemistry, the names of the compounds that are globally accepted are given according to the guidelines given by IUPAC for the nomenclature of organic compounds. The naming of aliphatic amines is done by prefixing the alkyl group to amines and thus the names of aliphatic amines are of the form of an alkylamine.

For examples, CH3NH2 is named as methylamine (alkyl part + amine =methylamine). Prefixes such as di and tri are appended before the names of the alkyl group when two or more identical groups are present. If more than one amino group is present in the amine then the parent chain and the position of amino groups is identified by numbering the carbon atoms in the parent chain.

The numbering is done in such a way that the carbon atom bearing the –NH groups get the lowest numbers.  Prefixes along with the numbers are then used to denote the number of amino groups and their position in the molecule. For example, H2N-CH2-CH2-NH is named as ethane 1, 2-diamine. If –NH2 group is attached to a benzene ring then it is called as arylamines.

One of the simplest examples of arylamine is C6H5NH2. It is commonly known as aniline which is also an accepted IUPAC name. When we name arylamines according to the guidelines given by IUPAC then ‘e’ of the arene is replaced by an amine, for example, C6H5-NHis named as benzenamine.

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