ABSTRACT
X-ray crystallography is a powerful analytical procedure that can provide three-dimensional structural information for any material which can form a single crystal. The X-ray diffraction data are collected on automatic, most often computer-controlled, diffractometers. The X-ray source is stationary but the crystal has three degrees of rotational freedom to move on the goniostat such that any diffracting plane in the crystal can be positioned at its Bragg angle to the incident X-ray beam. For any given molecule an X-ray diffraction analysis provides the structural formula, the stereochemistry, both lengths and bond angles, and conformational angles. The thermal modeling must be anisotropic to even approximately represent the true nature of the molecular vibrations occurring in a crystal. In addition to molecular connectivity and stereoconfiguration, the crystallographic structure determination produces numerical values for the bond distances, angles, and torsion angles occurring in the molecule in the crystalline state.
