The key difference between carbon NMR and proton NMR is that carbon NMR determines the type and the number of carbon atoms in an organic molecule whereas proton NMR determines the type and the number of hydrogen atoms in an organic molecule.
NMR is a chemical term we use in analytical chemistry to indicate Nuclear Magnetic Resonance. This term comes under the subtopic spectroscopy in analytical chemistry. This technique is very important in determining the type and number of particular atoms in a given sample. NMR technique is used mainly with organic compounds.
CONTENTS
1. Overview and Key Difference
2. What is Carbon NMR
3. What is Proton NMR
4. Side by Side Comparison – Carbon NMR vs Proton NMR in Tabular Form
5. Summary
What is Carbon NMR?
Carbon NMR is important in determining the type and number of carbon atoms in a molecule. In this technique, first, we need to dissolve the sample (molecule/compound) in a suitable solvent and then it can be placed inside the NMR spectrophotometer. Then the spectrophotometer gives us an image or a spectrum showing some peaks for the carbon atoms present in the sample. Unlike in proton NMR, proton-containing liquids can be used as the solvent since this method detects only carbon atoms, not protons.
Figure 01: Carbon NMR for Ethanoic Acid
Carbon NMR is useful in the study of spin changes in carbon atoms. The chemical shift range for 13C NMR is 0-240 ppm. To obtain the NMR spectrum, we can use the Fourier transform method. This is a fast process where a solvent peak can be observed.
What is Proton NMR?
Proton NMR is a spectroscopic method that is important in determining the types and number of hydrogen atoms present in a molecule. Therefore, it is also abbreviated as 1H NMR. This particular analytical technique includes steps of dissolving the sample (molecule/compound) in a suitable solvent and placing the sample with solvent inside the NMR spectrophotometer. Here, the spectrophotometer gives us a spectrum containing some peaks for the protons present in the sample and in the solvent as well.
However, the determination of protons present in the sample is difficult due to the interference coming from the protons in solvent molecules. Therefore, a solvent that does not contain any protons is useful in this method. For example, solvents containing deuterium instead of protons such as deuterated water (D2O), deuterated acetone ((CD3)2CO), CCl4, etc. can be used.
Figure 02: Proton NMR for Ethanol
The chemical shift range of 1H NMR is 0-14 ppm. In obtaining the NMR spectra for 1H NMR, continuous-wave method is used. However, this is a slow process. Since the solvent does not contain any protons, 1H NMR spectra have no peaks for the solvent.
What is the Difference Between Carbon NMR and Proton NMR?
The key difference between carbon NMR and proton NMR is that carbon NMR determines the type and the number of carbon atoms in an organic molecule whereas proton NMR determines the type and the number of hydrogen atoms in an organic molecule.
The following table summarizes the difference between carbon NMR and proton NMR.
Summary – Carbon NMR vs Proton NMR
Carbon NMR and proton NMR are two major types of nuclear magnetic resonance. The key difference between carbon NMR and proton NMR is that carbon NMR determines the type and the number of carbon atoms in an organic molecule whereas proton NMR determines the type and the number of hydrogen atoms in an organic molecule.
Reference:
1. “Progress In Nuclear Magnetic Resonance Spectroscopy.” Progress in Nuclear Magnetic Resonance Spectroscopy, vol. 40, no. 2, 2002, doi:10.1016/s0079-6565(01)00046-2.
2. Groves, Patrick, et al. “NMR Investigations of Lectin—Carbohydrate Interactions.” Lectins, 2007, pp. 51–73., doi:10.1016/b978-044453077-6/50004-1.
Image Courtesy:
1. “13C NMR ethanoic acid” By Chris Evans – D:\My Webs\index.htm, CC0) via Commons Wikimedia
2. “1H NMR Ethanol Coupling shown” By Andel – Own work, data from SDBSWeb: (National Institute of Advanced Industrial Science and Technology, accessed 2019-08-03) (CC0) via Commons Wikimedia