[dagree]

Hi

I've just bought some tributylphosphine to do a Mitsunobu reaction, but I want to test for impurities of tributylphosphine oxide. What is the best way to do this? Normally I would use NMR, but there doesn't seem to be that big of a difference between the two compounds. Any suggestions?

[macman104]

Do you have ³¹P NMR capabilities?  I imagine those shifts would be quite different.  I suppose you could try GC, don't have a lot of experience to tell if those will fly though.

[dagree]

No 31P unfortunately. I've tryed GC/MS and got two peaks of about the same intensity, but neither had the right mass, which is a bit puzzling.

[dagree]

BTW, it says on the bottle that it is a mixture of two isomers (?), which could explain the two GC-peaks, but not the missing mass peak.

[cundi]

Try HPLC.
Use reference standards of both of then

[dagree]

I just had a talk with our NMR-expert and it turns out that our equipment can be set up for 31P NMR, so I'll give that a try.

[dagree]

³¹P NMR showed one large peak at -30 ppm (and a couple of smaller ones), which fits the un-oxidized Bu₃P - yay