Matrix-isolated (MI) Fourier transform infrared spectra have been collected on a series of aliphatic ketones. The values for the carbonyl absorptions maxima are intermediate between vapor-phase (VP) and solid-state solution (SS) phases. The data reveal a stereochemical influence on
the position of the ketone carbonyl absorption when the carbons that are in the alpha position with respect to the carbonyl group contain alkyl substituents vs. protons. Steric bulk causes the frequency of the absorption to decrease. The position of the ketone carbonyl absorption was also
shown to decrease as the carbonyl group migrated toward the center of a long straight-chain hydrocarbon backbone. Stereochemical influences due to ring strain were also documented. Unsaturation, located in the alpha position with respect to the carbonyl, was shown to reduce the absorption
frequency. The trends found in this MI study are comparable to those previously documented from VP and SS studies. In two cases wherein very bulky substituents were located in the alpha position with respect to the carbonyl, a splitting of the carbonyl absorption was observed. Studies are
underway to test for a general trend in and to uncover an explanation for this phenomenon.
R. J. Reynolds Tobacco Company, Bowman Gray Technical Center, Winston-Salem, North Carolina 27102
Publication date: September 1, 1987
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