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Introductory Organic Chemistry - Lecture 6

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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?"

Prof. J. Michael McBride
CHEM 125: Freshman Organic Chemistry, Fall 2008
(Yale University: Open Yale)
Date accessed: 2009-11-11
License: Creative Commons BY-NC-SA

Lecture Material

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