NMR8. Chemical Shift in 1H NMR

The trends here are exactly the same as in carbon spectra. Wherever the carbon goes, it takes the proton with it. By analogy with carbon spectra,

• hydrogens on sp³ carbons usually show up in the upfield half of the spectrum, about 0 to 5 ppm.
• hydrogens on sp² carbons usually show up in the downfield half of the spectrum, about 5 to 10 ppm.
• within these two halves of the spectrum, electronegative atoms attached to the same carbon as a proton will draw that proton downfield.

Figure NMR11.¹H NMR spectrum of hexane.

Source: Simulated spectrum.

Figure NMR12.¹H NMR spectrum of 1-hexene.

Source: Simulated spectrum.

Figure NMR13.¹H NMR spectrum of butanal.

Source: Simulated spectrum.

As before, there are also hydrogens on linear carbons, although they are much less common than tetrahedral or trigonal carbons.

• hydrogens on sp carbons show up between 2 and 6 ppm.

Remember, these are general rules that you should know. There will occasionally be exceptions; the proton in a carboxylic acid may be seen at 12 ppm, and the proton in chloroform shows up at 7 ppm although it is attached to a tetrahedral carbon. (World-record shifts occur for hydrogens attached to transition metals: "late" metals like ruthenium or rhodium can move hydrogen peaks all the way up to -20 ppm, but "early" metals like tantalum can move them down as far as 25 ppm.)

Contributors and Attributions

Chris P Schaller, Ph.D., (College of Saint Benedict / Saint John's University)