Organic Compounds 2 Nuclear Magnetic Resonance Spectroscopy

Whitesell, J.K. Stereochemical analysis of alicyclic compounds by C-13 NMR spectroscopy. 1. Chemistry, Physical organic 2. Nuclear magnetic resonance spectroscopy 3. Carbon... 

Determining the structure of an organic compound was a difficult and time-consuming process in the 19th and early 20th centuries, but powerful techniques are now available that greatly simplify the problem. In this and the next chapter, we ll look at four such techniques—mass spectrometry (MS), infrared (IR) spectroscopy, ultraviolet spectroscopy (UV), and nuclear magnetic resonance spectroscopy (NMR)—and we U see the kind of information that can be obtained from each. 

Hodson, J., The Estimation of the Photodegradation of Organic Compounds by Hydroxyl Radical Reaction Rate Constants Obtained from Nuclear Magnetic Resonance Spectroscopy Chemical Shift Data, Chemosphere, 17, 2339-2348 (1988). 

Hodson, J. 1988. The estimation of the photodegradation of organic compounds by hydroxyl radical reaction rate constants obtained from nuclear magnetic resonance spectroscopy chemical shift data. Chemosphere 17 2339-2348. 

Hawkes, G.E., Smith, R.A., and Roberts, J.D., Nuclear magnetic resonance spectroscopy carbon-13 chemical shifts of chlorinated organic compounds, J. Org. Chem., 39, 1276, 1974. 

Nuclear magnetic resonance spectroscopy (NMR) is one of the most powerful analytical methods for identification and structure elucidation of organic compounds. Since NMR spectra are recorded in solution, no phase transfer like in MS is necessary when coupled with LC techniques. Additionally, NMR is a non-destructive detection technique, allowing the analyte to be transferred for characterization using additional methods. As of today, LC—NMR coupling was used in a wide range of applications [65,66,67,68,69,70,71],... 

Today, organic chemists rely on an array of very powerful instruments that enable them to identify compounds in much less time. With use of these instruments, it is often possible to determine the structure of an unknown compound in less than an hour. Three of the most powerful techniques are presented in this and the following chapters. They are infrared spectroscopy and two related techniques proton and carbon-13 nuclear magnetic resonance spectroscopy. Spectroscopy is the study of the interaction of electromagnetic radiation (light) with molecules. 

The IR spectrum provides little information about the hydrocarbon part of the compound. However, this is exactly the information provided by nuclear magnetic resonance spectroscopy, discussed in Chapter 14. The combination of these two types of spectroscopy is of enormous value in organic chemistry. 

Nuclear magnetic resonance spectroscopy (NMR) is the most powerful tool available for organic structure determination. Like infrared spectroscopy, NMR can be used with a very small sample, and it does not harm the sample. The NMR spectrum provides a great deal of information about the structure of the compound, and many structures can be determined using only the NMR spectrum. More commonly, however, NMR spectroscopy is used in conjunction with other forms of spectroscopy and chemical analysis to determine the structures of complicated organic molecules. 

Part Nuclear Magnetic Resonance Spectroscopy by W. Robien focuses on structure elucidation of organic compounds. Spectra similarity searches, spectrum prediction (from a given chemical structure), recognition of substructures and automatic isomer generation are the main topics they are still areas of scientific research in computer-assisted structure elucidation. 

Fanso-Free SNY, Furst GT, Srinivasan PR, Lichter RL, Nelson RB, Panetta JA, Gribble GW (1979) Organic structure characterization by natural-abundance nitrogen-15 nuclear magnetic resonance spectroscopy. Rauwolfia alkaloids and model compounds. J Am Chem Soc 101 1549-1553... 

---