[Baileys]

Are the signal intensities (of the peaks) in both 13C and 1H NMR spectra proportional to the number of carbon and hydrogen nuclei?

I am a little confused about whether the heigh of an NMR peak gives an indication as to how many C or H nuclei their are in that environment, i.e. a peak of strong intensity indicates many C or H nuclei compared to a peak of low intensity. One person has told me that the height of the peaks are not relevent at all, whereas someone else has said that they are (which I think must be the case myself). I know sometimes H spectra tells you the number of H nuclei by intergration, whereas C spectra do not. Please could you confirm for me what is actually true here.

[orgopete]

While it is possible to obtain quantitative 13C-NMR spectra, the long relaxation times of carbon and low concentrations make this a considerably more difficult task. It is far easier to use acquisition conditions that obtain spectra that show the peaks without their heights being proportional to their numbers.

Even the integral ratios in proton NMR spectra are not necessarily quantitive as obtained routinely.

[helenn]

Generally on proton NMR the integration gives the relative numbers of protons, but the actual height of the peaks you see is not always relative to the integration, if that makes sense.

The heights of the peaks in carbon nmr do not relate to the number of carbons.

[AC Prabakar]

propably the following Link may be helpful..

"http://www.org.chemie.tu-muenchen.de/people/rh/h1book/html.txt/english/53.shtml"