Calculate J-Value in NMR data? (And how to report the peak)?

Question

Let's say I have a doublet with 2 peaks: one at 0.9 ppm and one at 1.1 ppm. How do I report this peak, and how do I calculate the J value?

I'm pretty sure it's like the difference of chemical shifts (0.2 ppm) times the power of the magnetic field (let's say 400 MHz). So then I would get 80? (0.2 parts per million times 400 million = 0.2*400 = 80)? 80 what? Hertz?

Then do I report that as: 1H NMR (400 MHz/CDCl3) δ 1 (d, J = 80.0 [WHAT UNIT HERE? HZ?], 1H)
Or would I report it using the most upfield or downfield peak, rather than the average?

Do I just report a range for multiplets?

Thanks for the help!

Answer 1

For your hypothetical peak, you would report it as follows:



1H-NMR (CDCl3) d: 1.0 ppm (d, integration value, Jch value)



You always report the average ppm value. You do not need to report the frequency used because the coupling is independent of the magnetic field of the instrument. Although your J calculation is correct it seems a bit high for an H-H coupling. However, if it is a C-H coupling then it is fine. Finally, you would report this coupling in units of Hz.

For multiplets you will report the value that resides on the midpoint of the multiplet.

Answer 2

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RE:

Calculate J-Value in NMR data? (And how to report the peak)?

Let's say I have a doublet with 2 peaks: one at 0.9 ppm and one at 1.1 ppm. How do I report this peak, and how do I calculate the J value?



I'm pretty sure it's like the difference of chemical shifts (0.2 ppm) times the power of the magnetic field (let's say 400 MHz). So then I...

Answer 3

rhombohedral (welcome back!) has it correct and JH = 80 Hz is not an H-H coupling. In order for it to be H-H coupling you must have another doublet in the spectrum with the same coupling. My guess is that this is two singlets (CH3 groups?). It is not C-13 coupling because C-13 is only 1.1% natural abundance. Could be F-19 coupling (report as H NMR δ 1.00 (d, JFH = 80 Hz use superscript before J to indicate two- or three-bond coupling) no need for ppm as it is understood (δ). Could also be P-31 coupling but both couplings have to be two bond for that size!