Amines www.gneet.com 1 AMINES Amine may be regarded as derivative of ammonia formed by replacement of one or more hydrogen atoms by corresponding number of alkyl or aryl group CLASSIFICATION 1. Ammonia 2. Primary amine 3. Secondary When two hydrogen atoms are replaced by two alkyl or aryl groups. 4. Tertiary amine STRUCTURE OF AMINO GROUP Nitrogen atom of amino group is sp 3 hybridised. Three of these orbitals get involved in sigma bond formation with other atoms where as the fourth orbital contains lone pair of electrons Due to presence of unshared pair of electron, the angle is less than 109.5 o The angle around N atom in amines is not fixed and depends upon the number and size of alkyl group bonded to N atom. Therefore, in 1 o and 2 o amines, the bond angle between any two H atoms ( in 1 o ) or alkyl group (in 2 o ) decreases from the tetrahedral angle of 109 o 28’ to 107 o In case of 3 o amines, the three bulky alkyl group around N atom due to steric hinderance, the bond angle increases from 107 o to 108 o in trimethylamine
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Amines www.gneet.com
1
AMINES
Amine may be regarded as derivative of ammonia formed by replacement of one or
more hydrogen atoms by corresponding number of alkyl or aryl group
CLASSIFICATION
1. Ammonia
2. Primary amine
3. Secondary
When two hydrogen atoms are replaced by two alkyl or aryl groups.
4. Tertiary amine
STRUCTURE OF AMINO GROUP
Nitrogen atom of amino group is sp3 hybridised. Three of these orbitals get
involved in sigma bond formation with other atoms where as the fourth
orbital contains lone pair of electrons
Due to presence of unshared pair of electron, the angle is less than 109.5o
The angle around N atom in amines is not fixed and depends upon the
number and size of alkyl group bonded to N atom. Therefore, in 1o and 2o
amines, the bond angle between any two H atoms ( in 1o) or alkyl group (in 2o)
decreases from the tetrahedral angle of 109o28’ to 107o
In case of 3o amines, the three bulky alkyl group around N atom due to steric
hinderance, the bond angle increases from 107o to 108o in trimethylamine
Amines www.gneet.com
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Amines www.gneet.com
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ISOMERISM
1. Functional Isomerism: This is due to presence of different functional groups
Molecular formula C3H9N represent three functional isomers
Primary
CH3 – CH2 – CH2 – NH2 ( n- propyl amine 1o)
Secondary
Tertiary
2. Chain isomerism : This is due to difference in the carbon skeleton of the alkyl