Q104E - Chemistry (OpenStax)

Question

There are three possible structures for \({\rm{PC}}{{\rm{l}}_{\rm{2}}}{\rm{\;}}{{\rm{F}}_{\rm{3}}}\)with phosphorus as the central atom. Draw them and discuss how measurements of dipole moments could help distinguish among them.

Step-by-Step Solution

Answer

The three possible structures of \({\rm{PC}}{{\rm{l}}_{\rm{2}}}{\rm{\;}}{{\rm{F}}_{\rm{3}}}\) are:

Step 1: Definition of Concept

Two types of bonds in trigonal bipyramidal structures are found : axial bonds and equatorial bonds. In total, there are five bonds in the trigonal bipyramidal geometry.

 

Step 2: Draw three possible structures

The three possible structures of \({\rm{PC}}{{\rm{l}}_{\rm{2}}}{\rm{\;}}{{\rm{F}}_{\rm{3}}}\) are as follows: 

 

1) Both chlorine atoms lie along axial bonds, while F atoms lie along equatorial bonds.

Because the structure is symmetrical in this case, the molecule's dipole moment is zero.

 

2) One chlorine atom is in an equatorial position, while the other is in an axial position.

The structure is not symmetrical in this case, and there is some net dipole moment.

 

3) Both chlorine atoms are connected by equatorial bonds.

The structure is asymmetrical in this case, and there is a net dipole moment in the downward directions that is greater in magnitude than the structure's dipole moment (2).

 

Therefore, by rearranging different atoms along different types of bonds, the possible structures of a compound with a central atom with five sigma bonds can be written.