In the Classroom
Teaching Three-Dimensional Structural Chemistry Using Crystal Structure Databases. 1. An Interactive Web-Accessible Teaching Subset of the Cambridge Structural Database Gary M. Battle* and Frank H. Allen Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, United Kingdom *
[email protected] Gregory M. Ferrence Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160
Knowledge of the three-dimensional (3D) nature of chemical compounds is fundamental to the education of every chemist. Without this knowledge, concepts such as conformation, stereochemistry, chirality, and the geometrical shapes of metal coordination spheres cannot be properly assimilated or understood. Studies have shown that 3D visualizations enhance students' conceptual understanding and spatial abilities (1-3). Yet, even at a time when high-resolution interactive 3D graphics are available via every home PC, chemical structures are still often taught using quasi-2D representations. These representations do not convey the levels of understanding, even wonder, opened up to students by the visualization and manipulation of “real” 3D images on their own computer screens. Additionally, the use of experimentally measured data is of great pedagogical value and has been shown to enhance student interest (4-6). The experimental error and statistical variation inherent in experimentally measured structural data provide students with the opportunity to deal with the uncertainties of chemistry. Commonly undergraduate researchers struggle with the reality that the chemistry they perform in the research laboratory seems to violate their conceptions of chemistry because classroom examples have instilled a bias that chemical structure should be “perfect”, that is, idealized. For crystalline materials, modern X-ray analysis is now the method of choice for the determination of 3D structure across the complete chemical spectrum, from metals and alloys, through ionic and molecular species to proteins and viruses. Crystal structure information can now be obtained in a matter of hours and days and at the small-molecule level is very precise: standard uncertainties of
