[Morphic flip]

Looking at data that would (somehow) tell you what isomer was facial and meridional, the data has 2 peaks for one isomer and 1 peak for the other isomer. How would I tell from the ppm data (chemical shift) was the facial isomer.
The elements are F and P (in PF3) and both have 100% spin I = 1/2
The other group is carbonyl.
So it must be to do with PF3 opposite (meridional) or next to (facial) each other??

I had to do PF3 without subscript 3 as something is blocking it on my PC.

[Dan]

The Ps in the fac isomer are equivalent - each P is cis to 2 Ps, trans to 1 CO and cis to 2 CO. The mer isomer has two inequivalent Ps (trans to each other, cis to 1 P, cis to 3 CO), and one unique (cis to 2 P, trans to 1 CO, cis to 2 CO).

[Morphic flip]

Thank`s.
If the set of data given showed 2 chemical shifts ( both the same value) for isomer 2 and 3. And another chemical shift for isomer 3, what would be isomer 2, what would be isomer 3?
So isomer 2 has one chemical shift, isomer 3 has 2 chemical shifts.
What would be the fac isomer, isomer 2 or 3?

[Dan]

 

Thank`s.
If the set of data given showed 2 chemical shifts ( both the same value) for isomer 2 and 3. And another chemical shift for isomer 3, what would be isomer 2, what would be isomer 3?
So isomer 2 has one chemical shift, isomer 3 has 2 chemical shifts.
What would be the fac isomer, isomer 2 or 3?

read my post again... How many different chemical shifts would you expect each isomer to have?

[Morphic flip]

I`m not sure how they match up to what you`ve put.
But guess at 2 for the fac, 3 for the mer?

[Dan]

Yes. Nuclei in equivalent environments resonate at the same frequency. So for the fac isomer, all the Ps (and all the Fs, you havent specified wherther it is a ³¹P or a ¹⁹F spectrum, but the appearance will be similar) are in equivalent environments => 1 signal.
In the mer, there are two distinct P (and F) environments => 2 signals.

Additionally, in the fac isomer the PF₃s are cis to two COs and trans to one other, and in the mer isomer, one of the PF₃s is cis to two COs and trans to one other - this is why you have a coincident signal.

[Morphic flip]

Thank`s for the well explained reply