Difference Between Primary Amines, Secondary Amines, and Tertiary Amines

Main difference

The main difference between primary amines, secondary amines and tertiary amines is that primary amines have one alkyl or aryl group attached to the nitrogen atom in their structure while secondary amines have two alkyl or aryl groups attached to the nitrogen atom. nitrogen in its structure. and tertiary amines have three alkyl or aryl groups attached to the nitrogen atom in their structure.

Primary Amines vs. Secondary Amines vs. Tertiary Amines

The structure of primary amines comprises an alkyl group attached to each nitrogen atom; Secondary amines structure consists of two alkyl groups attached to each nitrogen atom leaving a hydrogen atom attached to the nitrogen atom. However, for tertiary amines, the structure comprises three alkyl groups attached to each nitrogen atom, thus leaving no hydrogen atom attached to a nitrogen atom.

Primary amines are less basic than secondary and tertiary amines, but more basic than ammonia; Secondary amines are found to be more basic than all amines, including primary amines, tertiary amines, and ammonia, while tertiary amines are found to be less basic than secondary amines but more basic than primary amines and ammonia.

In primary amines, no significant steric hindrance is found; for secondary amines, considerable steric stickiness is also not found, but tertiary amines show steric hindrance due to alkyl groups attached to the same nitrogen atom. In naming primary amines, their alkyl or aryl groups are mentioned as a prefix; while naming secondary amines, it is necessary to mention the two attached alkyl or aryl groups in their name, however, while pronouncing tertiary amines, it is necessary to mention the three attached alkyl or aryl groups in their name.

Comparison chart

primary amines Secondary amines tertiary amines
Amines that have an alkyl or aryl group are called primary amines. Amines that have two alkyl or aryl groups attached to the nitrogen atom in their structure are called secondary amines. Amines that have three alkyl or aryl groups attached to the nitrogen atom in their structure are called tertiary amines.
Structure
An alkyl or aryl group is attached to the nitrogen atom in its structure. Two alkyl or aryl groups are attached to the nitrogen atom in its structure. Three alkyl or aryl groups are attached to the nitrogen atom in its structure.
Basicity
They are less basic than secondary and tertiary amines, but more basic than ammonia. They are more basic than all amines, including primary and tertiary amines, and ammonia. Tertiary amines are less basic than secondary amines but more basic than primary amines and ammonia.
steric hindrance
No major steric hindrance. Without great steric interruption. They show steric hindrance due to alkyl groups attached to the same nitrogen atom.
Nomenclature
Their alkyl or aryl groups are mentioned as a prefix. It is necessary to mention in its name the two alkyl or aryl groups attached. It is necessary to mention in its name the three attached alkyl or aryl groups.
What are primary amines?

Primary amines are the amines that contain only one alkyl or aryl group that is bonded to the nitrogen atom in their structure when an ammonia molecule is bonded to three hydrogen atoms, one of these hydrogen atoms dissociates with the nitrogen atom and is replaced by an alkyl or aryl group. An alkyl group is a functional group found in organic molecules.

Its structure can be explained because, as a hydrogen atom loses bond in this group, a vacant point is formed. This vacant place can be filled by another atom. In the case of the primary amine, this vacant space is filled by attaching to a nitrogen atom from the ammonia group, leading to the formation of primary amines. In the case of aryls, an aryl group always contains a ring.

The aryl group is classified as simple aromatic compounds where a hydrogen atom is removed from its group and leaves the vacant position for bonding with another atom. This vacant space is filled in this case with the ammonia group leading to the formation of primary amines.

In naming primary amines, their alkyl or aryl groups are mentioned as a prefix. As if a methyl group were present on a primary amine. The compound is called methylamine. But, if the amine contains more functional groups in its structure, they are given their substituent name. As for the amine group, the name of the substituent is “amino”.

Amines act as bases with the litmus test due to the presence of lone pairs on one of their nitrogen atoms that donate to protons. The process occurs when the amine reacts with water; they form OH ions by donating their lone pair to the hydrogen atom of H2O. Since bases are the compounds that release OH ions, amines act as bases following the same path.

The basicity of the amines is observed by checking the stability of the compound formed after the donation of lone pairs. When the lone pair is donated by primary amines, the nitrogen atoms gain a positive charge. The positive charge is reduced as electrons are withdrawn towards them. Since there is only one alkyl group on primary amines, they act less basic than secondary amines.

What are secondary amines?

Secondary amines are the amines that contain two alkyl or aryl groups that are attached to the nitrogen atom in their structure. When two of the hydrogen atoms become unbonded from the nitrogen atom (as the ammonia molecule is bonded to three hydrogen atoms) and it is replaced by alkyl or aryl groups, leading to the formation of secondary amines.

In the case of aryls, an aryl group always contains a ring. Aryl groups are classified as simple aromatic compounds where two hydrogen atoms are removed from their group leaving the position vacant for bonding with other atoms. The empty spaces are filled in this case with ammonia groups that lead to the formation of secondary amines.

The nomenclature of secondary amines differs in that both attached alkyl or aryl groups need to be mentioned in their name. As, N-ethyl-N-propylamine represents a secondary amine consisting of a nitrogen atom bonded to a hydrogen atom, an ethyl group and a propyl group.

Secondary amines also act basic but more basic than primary and tertiary amines. The basicity of amines is observed by checking the stability of the compound formed after lone pair donation and its acceptance of protons. Alkyl groups are electron donors. The nitrogen atom is reduced by the property of electron donating alkyls as they reduce nitrogen atoms. Therefore, this secondary amine behaves more basic compared to other forms of amine.

What are tertiary amines?

Tertiary amines are amines that contain three alkyl or aryl groups attached to a nitrogen atom in their structure. These amines are formed by substituting all three hydrogen atoms. Because they contain three hydrogen atoms attached to the nitrogen atom, these are replaced by alkyl or aryl groups, leading to the formation of secondary amines. Therefore, there is no hydrogen atom left in the ammonia structure.

In the case of aryls, an aryl group always contains a ring. The empty spaces in the aryls were filled in this case with the ammonia group which led to the formation of tertiary amines. The nomenclature of tertiary amines differs because all three attached alkyl or aryl groups must be mentioned in their name. For example, in the case of tributylamine, the nitrogen atoms are attached to three butyl groups, which can be represented as (CH3CH2CH2CH2)3N.

Tertiary amines act as basic but more basic than primary amines and ammonia, but less basic than secondary ones; this is due to steric adhesion as the three alkyl groups attached to a nitrogen atom. Alkyl groups are electron donors. The nitrogen atom is reduced by the property of electron donating alkyls as they reduce nitrogen atoms.

Key differences

  1. Primary amines have an alkyl or aryl group attached to the nitrogen atom; Secondary amines have two alkyl or aryl groups attached, but tertiary amines have three alkyl or aryl groups attached to a nitrogen atom.
  2. Primary amines consist of an alkyl group attached to each nitrogen atom; secondary amines consist of two alkyl groups attached to each nitrogen atom; however, tertiary amines consist of a structure of three alkyl groups attached to each nitrogen atom and are different from primary and secondary amines.
  3. Primary amines are less basic than secondary and tertiary amines; secondary amines are more basic than all amines, while tertiary amines are more basic than primary amines and ammonia but less basic than secondary amines.
  4. In primary amines, there is no significant steric hindrance; secondary amines are considerable steric hindrance, but tertiary amines show considerable steric hindrance.

Final Thoughts

Primary amines consist of one alkyl or aryl group, while secondary amines have two alkyl or aryl groups, while tertiary amines are bonded with three alkyl or aryl groups. All of them are attached to the nitrogen atom with its structure.

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