1H NMR VERSUS 13C NMR

 

 

 

 One of the greatest advantages of ¹³C-NMR compared to ¹H-NMR is the breadth of the spectrum - recall that carbons resonate from 0-220ppm relative to the TMS standard, as opposed to only 0-12 ppm for protons. 

 

Because of this, ¹³C signals rarely overlap, and we can almost always distinguish separate peaks for each carbon, even in a relatively large compound containing carbons in very similar environments. 

 

In the proton spectrum of 1-heptanol, for example, only the signals for the alcohol proton (H_a) and the two protons on the adjacent carbon (H_b) are easily analyzed.  The other proton signals overlap, making analysis difficult. 

In the ¹³C spectrum of the same molecule, however, we can easily distinguish each carbon signal, and we know from this data that our sample has seven non-equivalent carbons. (Notice also that, as we would expect, the chemical shifts of the carbons get progressively smaller as they get farther away from the deshielding oxygen.)

 

This property of ¹³C-NMR makes it very helpful in the elucidation of larger, more complex structures.