The Effect of Solvent on Spectra. II. Correlation of Spectral Absorption Data with Z-Values

Abstract

A number of electronic transitions in different solvents are compared with Z-values, an empirical measure of solvent polarity based on the c.-t. band of 1-ethyl-4-carbomethoxypyridinium iodide. It is possible to identify certain specific interactions between solute and solvent by this means. With the aid of several reasonable assumptions, and a knowledge of the difference in the free energy of solution of the pyridinium iodide complex dipole between isoöctane and water, it is possible to estimate the excited state dipole moments resulting from certain electronic transitions. The effect of solvent on the spectra of several cyclopropyl ketones has been investigated, and a band resulting from cyclopropyl conjugation unequivocally identified in this way. Methyl cyclopropyl ketone has a maximum at 1931 Å. in water; this information casts doubt on previously reported maxima attributed to the interaction of a cyclopropyl ring with a carbonyl group. © 1958, American Chemical Society. All rights reserved.