Chemistry 125A: Freshman Organic Chemistry I - Lecture 6: Seeing Bonds by Electron Difference Density- Professor J. Michael McBride
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?"
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