An Introduction to NMR Spectroscopy

Two common types of NMR spectroscopy are used to characterize organic structure  

Before you can leam how to use NMR spectroscopy to determine the structure of a compound, you need to understand a bit about the physics behind it. Keep in mind, though, that NMR stems from the same basic principle as all other forms of spectroscopy. Energy interacts with a molecule, and absorptions occur only when the incident energy matches the energy difference between two states. 

In a magnetic field, there are now two different energy states for a proton  

When an external energy source (hv) that matches the energy difference (A ) between these two states is applied, energy is absorbed, causing the nucleus to spin flip from one orientation to another. The energy difference between these two nuclear spin states corresponds to the low-frequency radiation in the RF region of the electromagnetic spectrum. 

Absorbing RF radiation causes the nucleus to spin flip. 

In Chapter 14 we continue our study of organic structure determination by learning about nuclear magnetic resonance (NMR) spectroscopy. NMR spectroscopy is the most powerful tool for characterizing organic molecules, because it can be used to identify the carbon-hydrogen framework in a compound. 

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Professor R. J. Abraham of the Department of Chemistry, University of Liverpool for permission to reproduce the block diagram of a high-resolution NMR spectrometer (Figure 11.3) from An Introduction to NMR Spectroscopy, Abraham, R. J., Fisher, J. and Loftus, P., John Wiley and Sons Ltd, Chichester. 

The standard monograph for those seeking an introduction to EPR spectroscopy. Frieboiin H 1993 Basic One- and Two-Dimensional NMR Spectroscopy (New York VCH) A basic introduction to NMR spectrai anaiysis. 

For an introduction to ESR spectroscopy, see Chapter 5 in R.V. Parish (1990) NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis Horwood, Chichester. 

Mooney, E F An Introduction to 19F NMR Spectroscopy, Heyden Sons, London, 1970... 

J.W. Akitt, NMR and Chemistry-An Introduction to Modern NMR Spectroscopy, Chapman Hall, London... 

C. Glaubitz, An introduction to MAS NMR spectroscopy on oriented membrane proteins, Concepts in Magnetic Resonance, 2000, 12, 137-151. 

This review starts with an introduction to the principles and techniques of solid-state NMR spectroscopy and the description of the most important experimental approaches for NMR investigations of solid catalysts in the working state (Sections II and III). Section IV is a summary of experimental approaches to the characterization of transition states of acid-catalyzed reactions under batch reaction conditions. 

Farrar, T.C. (1987). An Introduction to Pulse NMR Spectroscopy. Chicago Farragut Press. 

Related reviews have been published on the use of NMR in pesticide analysis ( 1), metabolic studies (2,2) drug metabolism (4,2), and medicinal cKemistry (6,7). Since nfost of these reviews as Well as many texts contain introductions to NMR, none will be presented here. Furthermore, an audio course on Fourier Transform NMR Spectroscopy is also available (8). Since structural characterization is often based on empirical correlations, we have found compilations of proton spectra by Aldrich, Sadtler, and Varian (9-11) and carbon spectra by Breitmaier et al. and Bruker (12,13) to be useful. Becker (14) has presented extensive lists oT references that contain useful compilations of NMR data (pp 77 and 106). Techniques... 

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