The #PH_3# molecule can be represented in a tetrahedral arrangement similar to #NH_3#. How does one #PH_3# molecule interact with other #PH_3# molecules?

1 Answer
Dec 14, 2016

Answer:

Hydrogen bonding does not operate in phosphine.........

Explanation:

For the ammonia molecule, there is a large difference in electronegativity between the hydrogen and nitrogen nuclei, and the nitrogen atom polarizes electron density towards itself, #""^(delta-)N-H^(delta+)#. The result? Intermolecular hydrogen bonding operates, which is why the boiling point of ammonia, #-33# #""^@C#, is relatively elevated.

On the other hand, there is not a great of electronegativity difference between the phosphorus atom, and the hydrogen atom. The #P-H# bond is relatively non-polar as a result.

And the consequence? Because of the reduced intermolecular interaction, the boiling point of phosphine is #-87.7# #""^@C#. This is even despite the fact that phosphine is a larger molecule than ammonia, with a larger, more polarizable electron cloud.

And thus dispersion forces only operate in phosphine.