Question

I don t understand NMR proton how we can use to find molecule? how convert ppm to hz and hz to ppm?

Answer 1

NMR is a very useful technique to find out the number of magnetically active nuclei in atoms e.g. ¹H, _¹³C, ₃₁P etc. In presence of strong magnetic field these magnetically active nuclei tend to align themselves with or against the magnetic field. As a result an enrgy gap is created. Now, we use a radio frequency to flip the spins and record the enrgy that is relased.

Since the changes obseved in NMR are very small, so it is useful to see it in terms of ppm (parts per million) rather than Hz.

Suppose we observed a signal at 2 ppm (2 X 10^-6) in 100 MHz (100 X 10⁶) spectrometer. We can covert it into Hz.

Its value in Hz is = 2 ppm X 100 MHz = (2 X 10^-6) (100 X 10⁶ Hz) = 200 Hz

Now, Suppose we observed a signal at 50 Hz in 100 MHz (100 X 10⁶) spectrometer. We can covert it into ppm.

Its value in ppm is = 50 Hz/(100 X 10⁶Hz) = 0.5 X 10^-6 = 0.5 ppm