Effects of methyl-substitution on the color of indenylidene anions: Correlation between P-HMO analysis and visible spectroscopy

CHED 388

William A. Fogle and Donald W. Carpenetti II, don.carpenetti@marietta.edu. Department of Chemistry, Marietta College, 215 Fifth Street, Marietta, OH 45750
During the course of synthesizing various 1- or 2-methyl substituted indene derivatives a striking color difference was observed. A solution of 1-methylindene treated with butyl lithium was observed to immediately result in a deep red solution while the corresponding un-substituted indene or 2-methyl substituted indene remained pale yellow in color or became only slightly darker respectively upon addition of 1.2 equivalents of butyl lithium. These compounds were analyzed using visible spectrocopy and modeled using group theory and perturbation HMO analysis to explain the observed color differences.