For any value of alkyl group (R), the correct order of basic character of the 1o,2o,3o amines and NH3 in gaseous phase of non polar solvent is:
The correct option is B 3o>2o>1o>NH3
In gaseous phase, the basic strength of the amines is based on the number of +I groups present in the compound. Higher the number of +I group, greater will be the basic strength of the compound. We know alkyl groups are +I groups. Hence, tertiary amines are more basic than secondary and they are more basic than primary amines.
So the decreasing order of basic strength of amines in gaseous phase follows the order,
for example: for R=−CH3 basicity order is given by (CH3)3N>(CH3)2NH>CH3NH2>NH3