Thread: Proton N.M.R

Can anyone give me a basic explanation of Proton n.m.r spectroscopy.

My basic understanding is that it compares how hydrogens are arranged on a molecule relative to TSM.

and that how a peak is shifted from the TSM determines what the hydrogen is bonded to.

Any crucial details i have missed out and could someone help improve my understanding

Yeah, basically you use proton NMR to look at where hydrogen atoms are on a molecule. Your sample is immersed in a very strong magnetic field, and the nuclei of all the atoms which have a magnetic moment (e.g., protons) align with or against the magnetic field (effectively), and both these two states have different energies. Irradiating the sample with radio waves (the frequency range of the energy difference) causes population of the higher energy level and then resonance which can be measured and analysed.

Every proton itself has the same resonant frequency, but this changes depending on where it is in the molecule. The magnetic field of the electrons surrounding the atom can 'shield' the nucleus, which changes the resonant frequency of the proton. This shielding effect is dependent on the electron density around the atoms nearby as well, and is responsible for the chemical shift which is used to assign spectra. The arbitrary 'zero' set is indeed tetramethylsilane (TMS), mostly because almost all protons you're likely to encounter in an NMR spectrum of an organic compound are on one side of this zero, and it's a very well defined single peak.

That's a bit more than just basic, but maybe you can pick out some bits you find useful. Or ask a question, I can answer them :P

Cheers dude thats really helpful,

haven't studied it in school yet but got set a question on identifying a particular organic compound where one of the "clues" was some data from an NMR.i was like what the hell is this