Geo-Scientist Prelims 2024 Chemistry Q23: Two types of F atoms in (CH₃)PF₄ are indistinguishable while in…

Two types of F atoms in (CH₃)PF₄ are indistinguishable while in (CH₃)₂PF₃, equatorially placed F atom is distinguishable from apical F atom with the help of ¹⁹F NMR spectroscopy. The reason for the same is

1. (a) (CH₃)PF₄ has a square pyramidal geometry while (CH₃)₂PF₃ has a trigonal bipyramidal geometry
2. (b) (CH₃)PF₄ has all equivalent hybrid orbitals but (CH₃)₂PF₃ has non-equivalent hybrid orbitals
3. (c) inductive effect of methyl groups is higher in (CH₃)₂PF₃ than in (CH₃)PF₄
4. (d) two methyl groups pose higher rigidity in the molecule to allow pseudorotation in (CH₃)₂PF₃