Predict, giving reasons the order of basicity of the following compounds:
(i) gaseous phase (ii) in aqueous solution.
`(CH_(3))_(3)N, (CH_(3))_(2)NH, CH_(3)NH_(2),NH_(3)`

Explanation

(i) In gaseous phase, basic character of amines increases with the increase in the number of electron the releasing alkyl groups due to +I effect the trend of basic character is `3^(@)gt2^(@)gt1^(@)gtNH_(3)`
Therefore `(C_(3))_(3)Ngt(CH_(3))_(3)NHgtCH_(3)NH_(2)gtNH_(3)`
(ii) In aqueous phase, solvatiion of ammonium cation occurs by water molecules, greater the size of ion, lesser will be the solvation and lesser will be the stability of ion.
So on combining +I effect and solvation effect. In aqueous phase trend changes to `2^(@)gt1^(@)gt3^(@), (CH_(3))_(2)NHgtCH_(3)NH_(2)gt(CH_(3))_(3)NgtNH_(3)`