¹³C NMR signals provide information similar to that gained from ¹H NMR spectra, with a few differences:

• The Chemical Shift, or where along the x-axis the signal is located. This is measured in δ, ppm downfield from the reference compound Me₄Si; this tells us about the chemical environment--what groups might be bonded to the carbon bearing the observed carbon nucleus. The chemical shift range is much broader for carbon (0-225 ppm, for most signals) than for proton (0-12 ppm)
• The integral is generally not as useful. It can be measured with an appropriate pulse sequence, but normally the proton decoupling done to simplify the spectrum creates wide disparities in the signal-per-carbon nucleus for different carbons.
• The coupling pattern is eliminated by proton decouplig (symbolized by {¹H} ), normally. Other pulse sequences such as DEPT can be used to identify how many protons are bound to each carbon. The coupling still exists, and provides the basis for a variety of 2D experiments to establish bonding relationships.

Select an NMR peak in the spectrum of methylphenylketone (marked in red along the top) to highlight the nuclei responsible for it in the structure to the right. grid on grid off show peak list Selections off

Look at several different molecules with different functional groups. Be sure to load the spectrum by clicking on the name before zooming/highlighting.
1-Hexene The sp² region is downfield. If you zoom in, each of the two vinyl carbons is distinguishable. The alkyl regiion (upfield) is straightforward.
Benzaldehyde The downfield singlet is the CHO carbon. The aromatic ring protons have more complex coupling in part due to the impact of the aldehyde conjugation.
Benzoic Acid The carbonyl band is at an upfield position (relative to ketones & aldehydes).
Phenylethyne The alkyne carbons are in a unique region; very little else shows peaks around 100 ppm.
Hexanenitrile Another sp carbon; the nitrogen deshields it but still upfield of most sp² carbons.
Ethyl Acetate The ester carbonyl is also in the same region as a carboxylic acid. The carbon next to the oxygen reflects the deshielding effect of an electronegative atom.
n-Butylamine Nitrogen being less electronegative, the downfield shift is not as large.

Normal modes calculated at the B3LYP/6-31G** level and assigned based on the calculated spectrum using Gaussian09. Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc., Wallingford CT, 2009.
¹H NMR spectra were taken either from the PLU spectral archive, or simulated based on data reported in the AIST Spectral Database for Organic Compounds.
Page last updated: 3/31/2015