Infrared-ultraviolet double-resonance spectroscopy

N. Guchhait, T. Ebata, and N. Mikami, Discrimination of rotamers of aryl alcohol homologues by infrared ultraviolet double resonance spectroscopy in a supersonic jet. J. Am. Chem. Soc. 121, 5705 5711 (1999). 

Janzen, C., Spangenberg, D., Roth, W., and Kleinermanns, K. (1999) Structure and vibrations of pheno HjOjyg studied by infrared ultraviolet and ultraviolet-ultraviolet double-resonance spectroscopy and ab initio theory. J. Chem. Phys., 110, 9898-9907. 

Obtain infrared and nuclear magnetic resonance spectra following the procedures of Chapters 19 and 20. If these spectra indicate the presence of conjugated double bonds, aromatic rings, or conjugated carbonyl compounds obtain the ultraviolet spectrum following the procedures of Chapter 21. Interpret the spectra as fully as possible by reference to the sources cited at the end of the various spectroscopy chapters. 

Diverse spectroscopic methods have been employed to characterise triterpenes. Ultraviolet (UV) and infrared (IR) spectroscopy are not very useful techniques in elucidating the structure of triterpenes, but the former gives information about compounds with conjugated double bonds and the latter may provide some information about substituents like the hydroxyl group, ester carbonyl group or a,p-unsaturate carbonyl. Other physical data may be of interest to characterise new compounds, but the use of modem spectroscopic methods of nuclear magnetic resonance (NMR) and mass spectroscopy (MS) are essential for the structural determination. 

Today, a number of different instrumental techniques are used to identify organic compounds. These techniques can be performed quickly on small amounts of a compound and can provide much more information about the compound s structure than simple chemical tests can provide. We have already discussed one such technique ultraviolet/visible (UVA/is) spectroscopy, which provides information about organic compounds with conjugated double bonds. In this chapter, we will look at two more instrumental techniques mass spectrometry and infrared (IR) spectroscopy. Mass spectrometry allows us to determine the molecular mass and the molecular formula of a compound, as well as certain structural features of the compound. Infrared spectroscopy allows us to determine the kinds of functional groups a compound has. In the next chapter, we will look at nuclear magnetic resonance (NMR) spectroscopy, which provides information about the carbon-hydrogen framework of a compound. Of these instrumental techniques, mass spectrometry is the only one that does not involve electromagnetic radiation. Thus, it is called spectrometry, whereas the others are called spectroscopy. 

The conformation of the double helix can be studied using various spectroscopic methods such as circular dichroism (CD) [34], infrared (IR), Raman, ultraviolet (UV), visible absorption spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy [35]. 

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