CHEM 125A - Freshman Organic Chemistry I
Lecture 06 - Seeing Bonds by Electron Difference Density. Professor McBride uses a hexagonal "benzene" pattern and Franklin's X-ray pattern of DNA, to continue his discussion of X-ray crystallography by explaining how a diffraction pattern in "reciprocal space" relates to the distribution of electrons in molecules and to the repetition of molecules in a crystal lattice. He then uses electron difference density mapping to reveal bonds, and unshared electron pairs, and their shape, and to show that they are only one-twentieth as dense as would be expected for Lewis shared pairs. Anomalous difference density in the carbon-fluorine bond raises the course's second great question, "Compared to what?" (from oyc.yale.edu)
| Lecture 06 - Seeing Bonds by Electron Difference Density |
| Time | Lecture Chapters |
| [00:00:00] | 1. Understanding Diffraction Patterns: Continuing the Case of the Hexagonal "Benzene" |
| [00:15:11] | 2. Double Helices and DNA: Even and Offset Planes |
| [00:29:04] | 3. Revealing Bonds and Unshared Electron Pairs via Electron Difference Density Maps |
| [00:43:23] | 4. The Second Great Question: "Compared with What?" |
| References |
| Lecture 6 - Seeing Bonds by Electron Difference Density Instructor: Professor J. Michael McBride. Resources: Professor McBride's website resource for CHEM 125 (Fall 2008). Transcript [html]. Audio [mp3]. Download Video [mov]. |
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