Question

why secondary amine is more basic then tertiary amine??

Answer 1

Amines are bases due to the lone pair of electrons on the nitrogen atom of amines. These react with water to form hydroxyl ions.
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Bases are those species that donate OH- ions (hydroxyl ions). The more easily is the availability of the hydroxyl ions; more is the basicity of the amine. 
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In tertiary amines there are large steric hindrance to the extent to hydrogen bonding in the conjugate base amine cation are formed .
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