What is the decreasing order of basicity of `1^(@)2^(@)` and `3^(@)` ethy1 amines and ammonia ?

Options

A. `(C_(2)H_(5))_(2)NH gt C_(2)H_(5)NH_(2) gt (C_(2)H_(5))_(3)N gt NH_(3)`
B. `(C_(2)H_(3))N gt (C_(2)H_(5))_(2)NH gt C_(2)H_(5)NH_(2) gt NH_(3)`
C. `(C_(2)H_(2))_(2)NH gt (C_(2)H_(5))_(3)N gt C_(2)H_(5)NH_(2) gt NH_(3)`
D. `NH_(3) gt C_(2)H_(5)NH_(2) gt (C_(2)H_(5))_(2)NH gt (C_(2)H_(5))_(3)N`

Answer

C

Explanation

In aq. Solution two factors operate simultaneously (i) inductive effect of alkyl group which tends to increase the basic strength and (ii) steric effect of alkyl group which tends to decrease the basic strength The combined effect of the two results in the following order
`NH_(3) lt C_(2)H_(5)NH_(2) lt (C_(2)H_(5))_(3)N lt (C_(2)H_(5))_(2)NH` .