[Dirac]

Hello to everyone:

I have some difficulties trying to find a  molecular structure from NMR data. The problem is this: I have a partial ¹H-NMR and ¹³Proton decoupled spectra. I have the molecular formula : C₈H₁₈O₂.

The first thing I've do is calculate the Index of Hydrogen Deficiency, in this case is zero. So, the molecule is saturated, no double or triple bond are present and it is nor aromatic or cyclic.

Then, I calculate the relative numbers of H in the proton-NMR spectrum, 4:2:6:6. Because the signal in this spectrum in the range of 3-4 ppm, I think that the molecule is an alcohol (diol), and for the numbers of signals in the ¹³C-NMR spectrum it is a symmetrical molecule.

The structures that I think respond to the data are in the image below. Also, I give the image of the spectra.

My problem is: The molecules make sense to the ¹³C-NMR spectrum, but not with the proton-NMR spectrum, this molecules do not have a singlet in the last one.

Can you give some tips to solve the problem?

PD: I'm sorry if my English is strange, it is not my mother tongue.

[Babcock_Hall]

You wrote, "this molecules do not have a singlet in the last one"  I am not sure what you mean.

Let us assume that your structure is correct for the sake of argument.  If so, then the four hydrogen atoms on the two central carbon atoms (carbon atoms 3 an 4) will not obey first-order rules for predicting H-1 NMR spectra.  Even if all four H atoms are isochronous (having the same chemical shift), they are not all magnetically equivalent.  Putting it another way, if the only problem you think you see in the H-1 spectrum is the appearance of these four hydrogen atoms, then I would not be concerned.  However, I have not checked whether the H atoms on C-2 and C-5 have predicted chemical shifts in the right region, so you might explore that question also.