I am synthesizing an azide substituted phosphonate and I am unsure whether I have the right product. Starting with a phosphonate (PO3C-R) with a resonance of 10 ppm in the 31P spectrum, what effect on the 31P shift would substitution of one or two azide (N3) cause?
Not sure about the shift in the P31 peak. But if the azido in in vicinity of the carbons around phosphorus..you may find the shift in carbon peak...
The carbons (alpha, beta and some time gamma) to the Phosphorus atom will show the doublet. And the coupling constant will decrease as the distance of carbon to phosphorus increases.
I think, if you can compare the carbons from your starting material and product, you will be able to sort out the change in structure.
Best luck!
It would be better if you explain exactly, which phosphonate and which azidophosphonate yoyu are talking about. You mean alpha-azidophosphonate?
Nevertheless, I'll give you some experimental details, which might be useful for you:
diethyl azido(phenyl)methylphosphonate - 31P NMR shift is around 20 ppm (Skropek et al., BMCL, 13(2003) 3351-3354)
diethyl amino(phenyl)methylphosphonate - 31P NMR shift is around 26 ppm (Skropek et al., BMCL, 13(2003) 3351-3354)
diethyl phenylmethylphosphonate (alternatively benzylphosphonate) - 31P NMR shift is around 26 ppm (Kedrovski, Daugherty, Org. Lett., 2010, 12(18), 3990-3993)
So, as you see, in this case, the azido group changed the shift to lower values of ppm, it is difficult to make a rule for it, however.
Check also the old paper: Gajda; Matusiak, Synthesis, 1992 , # 4 p. 367 - 368, but I have no access to old Synthesis issues, but in Texas you may have
If you gave me more details about your problem, I would help you with a pleasure.
If you wish, write directly to my e-mail: [email protected]
Thank you Dr. Lewkow. What I had in mind was an azide directly attached to the phosphorus atom. I would imagine that such an unusual electronic structure would cause a very significant shift in the 31P spectrum.
Dr Muller,
I'm answering using my smartphone as since yesterday I'm on holidays at the seaside. I cannot check anything, cos I have no appropriate tools at my smartphone.
In my opinion the 31P resonance will occur in lower ppm for your azides but it requires literature study. I can do it after I'm back from the seaside, i.e. around 6 August.
I'll contact you in August.
Best wishes,
Jaroslaw
Dear Jaroslaw, I was wondering whether you had had a chance to look into this matter. To follow up with another question: if the azide were an amine, where would we expect the ppm in the 31P spectrum? Would the amine protons actually split the 31P signal? Assuming we are not in a deuterating solvent.
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