[asa029]

Hi!

Because one of my compounds is virtually insoluble, one of the technicians have taken a solid state 1H-NMR sample of the compound. The spectrum looks okay, except for a discrepancy between shift values (about 2ppm from the same sample in CCl3D).

I was wondering if anyone had any experience on the subject and knows if the shift values for the protons can vary that much between normal NMR and solid state NMR.

[Honclbrif]

I don't have any experience with solid state, but chemical environment does have an effect on chemical shift. For instance, the alpha methyl protons in EtOAc can range from 2.07 ppm in D2O to 1.65 ppm in d6-benzene. If the protons are readily exchangeable the variation can be much greater.

EDIT: In the solid state, the chemical environment will probably be pretty different from the solvated environment, so I would expect to see some difference between the two.

[ATMyller]

solid state 1H NMR usually gives extremely broad signals due to chemical shift anisotropy and homonuclear dipolar coupling unless you are using extremely high spinning speeds and CRAMPS. Signals are several orders of magnitude broader than with liquid 1H NMR so any chemical shift value obtained is vague at best case. If you have sharp distinct signals (FWHM less than 10 ppm) in solid state 1H NMR they are most likely caused by a liquid species.

[asa029]

solid state 1H NMR usually gives extremely broad signals due to chemical shift anisotropy and homonuclear dipolar coupling unless you are using extremely high spinning speeds and CRAMPS. Signals are several orders of magnitude broader than with liquid 1H NMR so any chemical shift value obtained is vague at best case. If you have sharp distinct signals (FWHM less than 10 ppm) in solid state 1H NMR they are most likely caused by a liquid species.

We used spinning of 4KHz with magic angle, which radically de-broadened the signals. The peak width was still pretty large after spinning, though.