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n-butylamine(I), diethylamine(II) and N,...

n-butylamine(I), diethylamine(II) and N, N-dimethylethylamine(III) have the same molar mass. The increasing order of their boiling point is

A

a) `III lt II lt I`

B

b) `I lt II lt III`

C

c) `II lt III lt I`

D

d) `II lt I lt III`

Text Solution

Verified by Experts

The correct Answer is:
A
The boiling points of amines depends upon their degree of association and the degree of association is further depends upon the extent of H-bonding. Since `1^(@)` amines have two, `2^(@)` amines have one while `3^(@)` amines have no hydrogen atoms linked to nitrogen, therefore among isomeric amines, `1^(@)` amines have the highest, while `3^(@)` amines have the lowest boiling point. Thus, the increasing order of boiling point is
`underset("N, N-dimethylethylamine (III)")(CH_(3) - overset(CH_(3))overset(|)(N) - CH_(2) - CH_(2)) lt underset("diethylamine (II)")(CH_(3) - CH_(2) - NH - CH_(2) - CH_(3)) lt underset("n-butylamine (I)")(CH_(3) - CH_(2) - CH_(2) - CH_(2) - NH_(2))`
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