The application of the methods which are described in the previous paper to the determination of the intensities of C-0 stretching bands in steroids is illustrated. Correlations between band intensities and molecular structures have been established on the basis of measurements on 66 steroids. The integrated absorption intensities of different types of carbonyl g-roups vary by a factor of four but the intensity for a given type of carbonyl group is sensibly constant in different compounds. The ketone intensity does not vary appreciably with the position of the carbonyl group in the steroid nucleus, but is significantly different when the carbonyl group is in a side chain. Systematic changes in intensity are ohserved when the carbonyl group is conjugated or when a halogen atom is introduced at a vicinal methylene group. In the di-and polycar-bony1 compounds investigated the carbonyl intensities were found to be additive within the limits of experimental error. Such measurements permit the number of carbonyl groups in a compound to be determined even where the bands overlap completely, and have been applied to the elucidation of the structure of steroids isolated from natural sources. Integrated absorption intensities are found to give more satisfactory structural correlations than maximal molecular extinction coefficients.
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