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QJEEAdv24Ch9d77: JEE Advanced 2024 Chemistry - Class 12 JEEAdv24Ch9d77 Solution: The species formed on fluorination of phosphorus pentachloride…

The species formed on fluorination of phosphorus pentachloride in a polar organic solvent are

Multiple Choice Options

  • A [PF4]+[PF6]−\left[\mathrm{PF}_4\right]^{+}\left[\mathrm{PF}_6\right]^{-} and [PCl4]+[PF6]−\left[\mathrm{PCl}_4\right]^{+}\left[\mathrm{PF}_6\right]^{-}
  • B [PCl4]+[PCl4 F2]−\left[\mathrm{PCl}_4\right]^{+}\left[\mathrm{PCl}_4 \mathrm{~F}_2\right]^{-} and [PCl4]+[PF6]−\left[\mathrm{PCl}_4\right]^{+}\left[\mathrm{PF}_6\right]^{-}
  • C PF3\mathrm{PF}_3 and PCl3\mathrm{PCl}_3
  • D PF5\mathrm{PF}_5 and PCl3\mathrm{PCl}_3

Step-by-Step Verified Solution

When PCl5\text{PCl}_5 is fluorinated in a polar organic solvent, it forms ionic isomers. The formation of these ionic species can be understood as follows:

  1. PCl5\text{PCl}_5 in a polar organic solvent can dissociate into ionic forms, such as [PCl4]+\left[\text{PCl}_4\right]^+ and [PCl6]−\left[\text{PCl}_6\right]^- .

  2. Upon fluorination, PCl5\text{PCl}_5 can be converted into [PF6]−\left[\text{PF}_6\right]^- and [PCl4]+\left[\text{PCl}_4\right]^+ .

  3. Further fluorination can lead to the formation of mixed ionic compounds where PCl5\text{PCl}_5 can form isomers like [PCl4]+[PCl4F2]−\left[\text{PCl}_4\right]^+ \left[\text{PCl}_4 \text{F}_2\right]^- .

The two ionic isomers formed are:

  1. [PCl4]+[PCl4F2]−\left[\text{PCl}_4\right]^+ \left[\text{PCl}_4 \text{F}_2\right]^- , which are colorless crystals.

  2. [PCl4]+[PF6]−\left[\text{PCl}_4\right]^+ \left[\text{PF}_6\right]^- , which are white crystals.

Hence, the ionic isomers formed when PCl5\text{PCl}_5 is fluorinated in a polar organic solvent are :

Option B : [PCl4]+[PCl4F2]−\left[\text{PCl}_4\right]^+ \left[\text{PCl}_4 \text{F}_2\right]^- and [PCl4]+[PF6]−\left[\text{PCl}_4\right]^+ \left[\text{PF}_6\right]^-

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