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Linné on line arrow Linnaeus and Pharmacy arrow Chemistry in nature arrow To determine the structure

To determine the structure

Element analysis
gives the proportions in percentage of the various elements that form a substance. This makes it possible to calculate how many atoms of carbon, hydrogen, oxygen and so on, that make up the molecule.

Ultraviolet spectroscopy
Absorption of light in the ultraviolet region of wave lengths; different chemical groups absorb light in different regions of wave length which means that information can be found concerning the chemical structure.

Infrared spectroscopy
Absorption of light in the infrared wave length region; different chemical groups absorb light in different regions of wave length which means that information can be found concerning the chemical structure. Above all this applies to functional groups, e.g., amino, alcohol and acid groups.

Mass spectrometry
This is a method to determine the size or mass of a molecule. The substance to be examined is charged with electrons. As a result, it fractures into fragments of different sizes. These are then sucked into a bent tube through which an electric field is passed. By varying the electric field, it is possible to determine the size of the fragments that pass through the tube. Those that are too light hit one of the walls, while those that are too heavy hit the other. In this way you can form a picture of how common the various fragment sizes are. The appearance of certain fragments when charged with electrons depends upon the structure of the original substance.

Nuclear magnetic resonance spectroscopy
Here you expose a substance to a very strong magnetic field for a short moment. The electrons have charges that cause them to react like very small magnets and turn them towards the big magnet. When the magnetic field is turned off and stops affecting the electrons, they “slowly” revert to their original positions. The different times that it takes for them to revert to where they started from, depends on where the individual electrons are within the molecule. This is registered and then converted to a spectrum of peaks on a scale from which it is possible to determine the structure of a substance.

Derivation
You can even study what happens when the substance is exposed to different chemical reagents. Substances react differently to different chemical reagents according to their functional groups. If you use spectroscopic methods to study the derivatives that have been produced, you will be able to see the changes and draw conclusions about the structure.

Reference comparisons
It is also possible to compare the chromatographic properties of the substance to a reference. In this way you can see if they behave in the same way. In addition, you can compare the spectroscopic behaviour of the reference to the same substance in an authorised reference database of substances.

Examinations of the structures of chemical substances are carried out at the Faculty of Pharmacy, Uppsala University, principally at the Department of Medicinal Chemistry.