Question

Arrange the following amines in the increasing order of basicity : n-Butylamine (I), sec-Butylamine (II), Isobutylamine (III), tert-Butylamine IV. Explain.

Answer 1

Sterric hindrance decrease the availability of lone pair on nitrogen atom which in turn decreases the basic character. Thus, increasing order of basic character is : IV<III<II<I.

+I effect of the alkyl group is in a direction opposite to that due to sterric hindrance i.e., +I effect of tert-butyl group is maximum thus (IV) is the most basic while it is least for (I) hence least basic.