Question

Which one of the following is correct with respect to basic character?
which one of the following is correct with respect to basic character?
A.$P{(C{H_3})_3} > P{H_3}$
B.$P{H_3} > P{(C{H_3})_3}$
C.$P{H_3} > N{H_3}$
D.$P{H_3} = N{H_3}$

Answer 1

Hint: As we know that according to Lewis definitions of acids and bases, an acid is that which gains an electron pair and a base is the one that donates an electron pair. On going down the group basicity increases as the electrons can be easily donated and methyl groups serve as donors of electrons.

Complete Step by step answer: As we know that according to Lewis definitions of acids and bases, an acid is that which gains an electron pair and a base is the one that donates an electron pair. Thus phosphine is more basic than ammonia. But as we have learnt that if the bulky group is present it will show positive inductive effect. Three Methyl groups are present in $P{(C{H_3})_3}$ they tend to increase the overall electron density on this molecule making the molecule more donating in nature and thus behaves as a basic molecule. $P{H_3}$ is a weak base because it does not possess any lone pair and it even does not hydrolyze easily in water to produce hydroxide whereas ammonia is stronger base than phosphine because it contain lone of pair of electrons which helps it to serve as a base. Hence, except first all the three options are incorrect.

Therefore the correct answer is (A).

Note: When the molecules is attached with a number of $ - I$ groups the acidity of the molecule increases as they make the molecule electron deficient and when the molecule is attached with a number of $ + I$-groups then the basicity increases as they tends to make the molecule electron rich and electron donor.