Arrange `1^(@), 2^(@) and 3^(@)` amines in increasing order of their basicity and give reasons (in non-aqueous solvents or in vapour state).

Explanation

Aliphatic amines are stronger bases than ammonia `(K_(b)=1.8xx10^(-5))`. This can be explained on the basis of the `+I` effect or electron-donating effect of alkyl attached to the nitrogen atom. This increase the electron density on the nitrogen atom. Thus, amines can donate the lone pair of electrons more easily than ammonia.
`underset("Ammonia")(H-undersetunderset(H)(|)overset(..)N-H)`
Moreover, electron releasing effect of alkyl groups stabilises the alkyl ammoniumion formed and hence, shifts the equilibrium in the formed direction making the alkyamines stronger bases then ammonia
In non-aqueous solvents or invapour state, the basic character of amines increases with increase in the number of R-groups. Thus, order of basic character is `NH_(3)lt1^(@)"Amine"lt2^(@)"Amine"lt3^(@)` Amine.