24. Determining Chemical Structure by Isomer Counting (1869)

Freshman Organic Chemistry (CHEM 125)

Half a century before direct experimental observation became possible, most structures of organic molecules were assigned by inspired guessing based on plausibility. But Wilhelm Körner developed a strictly logical system for proving the structure of benzene and its derivatives based on isomer counting and chemical transformation. His proof that the six hydrogen positions in benzene are equivalent is the outstanding example of this chemical logic but was widely ignored because, in Palermo, he was far from the seats of chemical authority.

00:00 - Chapter 1. How Did Kekule Know Benzene is Hexagonal?
20:10 - Chapter 2. Koerner's System of Isomer Counting and Chemical Transformation
29:53 - Chapter 3. Koerner's Assumptions on Replacement and Experimental Distinguishability
34:22 - Chapter 4. The Koerner Equivalence Proof

Complete course materials are available at the Open Yale Courses website: http://open.yale.edu/courses

This course was recorded in Fall 2008.