15. Chemical Reactivity: SOMO, HOMO, and LUMO

Freshman Organic Chemistry (CHEM 125)

Professor McBride begins by using previous examples of "pathological" bonding and the BH_3 molecule to illustrate how a chemist's use of localized bonds, vacant atomic orbitals, and unshared pairs to understand molecules compares with views based on the molecule's own total electron density or on computational molecular orbitals. This lecture then focuses on understanding reactivity in terms of the overlap of singly-occupied molecular orbitals (SOMOs) and, more commonly, of an unusually high-energy highest occupied molecular orbital (HOMO) with an unusually low-energy lowest unoccupied molecular orbital (LUMO). This is shown to be a generalization of the traditional concepts of acid and base. Criteria for assessing reactivity are outlined and illustrated.

00:00 - Chapter 1. Introduction: "Pathological" Bonding in the BH3
10:45 - Chapter 2. Viewing BH3 via Electron Density and Molecular Orbitals
20:25 - Chapter 3. Assessing Reactivity through HOMO-LUMO Interactions
40:15 - Chapter 4. Criteria for Assessing Reactivity

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

This course was recorded in Fall 2008.