Question

Arrange the following.

In decreasing order of basic strength in gas phase (C₂H₅)NH₂, (C₂H₅)NH, (C₂H₅)₃N and NH₃.

Answer 1

In the gas phase, solvent effects i.e., stabilization of the conjugate acids due to H-bonding, are absent. Therefore, in the gas phase, basic strength mainly depends upon the +I effect of the alkyl groups. Since the +I effect increases with the number of alkyl groups, therefore the basic strength of the amines decreases as the number of ethyl groups decreases from three in (C₂H₅)₃N to two in (C₂H₅)₂NH to one in C₂H₅NH₂ and zero in NH₃.

Basic strength in the gas phase decreases in the order is, (C₂H₅)₃N > (C₂H₅)NH₂ > (C₂H₅)NH > NH₃.