What is absolute structure determination?

What is absolute structure determination?

A standard crystallographic X-ray diffraction experiment yields information about the three dimensional spatial arrangement of atoms within a crystal, revealing the relative stereochemistry of all chiral centres within a molecule. If a crystal consists of molecules of an enatiomerically pure substance (for example naturally occuring sucrose or tartaric acid) then it is possible with a careful experiment to determine the absolute stereochemistry of chiral centres within a molecule. The experiment requires a longer wavelength of X-rays, and a more time-consuming data collection.