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Question: The correct order of basicity of amines in water is :...

The correct order of basicity of amines in water is :

A

(CH3)2NH>(CH3)3N>CH3NH2(CH_{3})_{2}NH > (CH_{3})_{3}N > CH_{3}NH_{2}

B

CH3NH2>(CH3)2NH>(CH3)3NCH_{3}NH_{2} > (CH_{3})_{2}NH > (CH_{3})_{3}N

C

(CH3)3N>(CH3)2NH>CH3NH2(CH_{3})_{3}N > (CH_{3})_{2}NH > CH_{3}NH_{2}

D

(CH3)3N>CH3NH2>(CH3)2NH(CH_{3})_{3}N > CH_{3}NH_{2} > (CH_{3})_{2}NH

Answer

(CH3)2NH>(CH3)3N>CH3NH2(CH_{3})_{2}NH > (CH_{3})_{3}N > CH_{3}NH_{2}

Explanation

Solution

Basicity of amines increase with increase in number of −CH3- CH_{3} groups (or any group which cause +I effect), due to increase in electron density on N atom. As a rule, the basicity of t-amine should be more than that of s-amine, but actually it is found to be lesser than s-amines. This is due to stearic hinderence of bulkier alkyl groups, which decreases the availability of lone pair of electron on the N atom of the amino group. Hence the correct order of basicity is :

(CH3)2NH>(CH3)3N>CH3NH2(CH_{3})_{2}NH > (CH_{3})_{3}N > CH_{3}NH_{2}