CHEM 125a - Lecture 6 - Seeing Bonds by Electron Difference Density

Lecture 6 - 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?"


Professor McBride's website resource for CHEM 125 (Fall 2008)

This website may include third-party materials pertaining to relevant topics, provided for the user's convenience. Yale does not control or take responsibility for the content of any off-site pages or linked sites.


Reading assignments, problem sets, PowerPoint presentations, and other resources for this lecture can be accessed from Professor McBride's on-campus course website, which was developed for his Fall 2008 students. Please see Resources section below.

Course Media





Low Bandwidth Video

mov [100MB]

High Bandwidth Video

mov [500MB]