Number of Different Carbons

4-Methyl-2-pentanone contains 6 carbons and some of them are different from each other.

For example, the carbon labeled A is attached to a carbonyl group and no other carbons. Carbon B is the carbon of a ketone carbonyl group. Carbon C is a carbon attached to both a carbonyl carbon and a methine (-CH-) carbon. Carbon D is attached to three other sp3 carbons. The carbons labeled E are both attached to carbon D.
Just like in 1H-NMR, every chemically distinct carbon or group of carbons will give a unique resonance in the NMR spectra. You may want to use the model to the right to help you figure out which carbons are the same or different. As mentioned, since common carbons resonate over such a wide range (0-200 ppm) as compared to protons, it is unlikely that two carbons will resonante exactly at the same place (which is not very true of protons). Therefore, one can tell how many different carbons or groups of identical carbons exist in a molecule simply by counting the number of resonances in the 13C NMR spectra.
To start animation, right-click on the above molecular model and select Animation, Start.
Highlight the carbon labeled A
Highlight the carbon labeled B
Highlight the carbon labeled C
Highlight the carbon labeled D
Highlight the carbon labeled E