| Themes > Science > Chemistry > Organic Chemistry > Determination of Structure > Determination of Structure |
The use of chemical reactions to identify the structures of organic compounds has been replaced largely by instrumental methods since 1940. Infrared spectra are used to identify functional groups, and ultraviolet spectroscopy can distinguish aromaticity and certain kinds of unsaturation in a molecule. A nuclear magnetic resonance (nmr) spectrum gives the largest amount of information about the structure of a compound; infrared and ultraviolet spectra complement rather than duplicate such data. Proton resonance spectroscopy is sometimes used to determine the nature of the local environment of the hydrogen atoms in a molecule and it can often simultaneously supply the ratios of types of hydrogen. More recently, carbon-13 nuclear magnetic resonance spectroscopy has been used to derive complementary information to the proton data. Also, an X-ray spectrum may be necessary to determine three-dimensional aspects of structure in a complex organic molecule. |
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