The Intensities of Carbonyl Bands in the Infrared Spectra of Steroids¹

Abstract

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.

Integrated Intensities of Absorption Bands in Infrared Spectroscopy

“…Part of the variation may be due to differences in extrapolation range, background correction, method of integration, concentration effects, and instrumental and sampling errors. The intensity of the acetate group was 1.40 units in acetylated steroids and 1.2 units in the phenyl acetate derivatives [15], in fair agreement with values in Table 20 for each structural type.…”

“…The effect of a vicinal halogen is to lower the intensity either by an inductive effect, as in the keto steroids [15], or by a field effect, as in the equatorial conformation of a-bromocyclohexanone [23].…”

Carbon Disulfide. III. Reaction with Active Methylene Compounds. The Infrared and Ultraviolet Spectra of the Desaurins

“…The sum of the integrated intensities of the bands at 6.13 and 6.18 p of 12 in solution in chloroform was determined to be 1.39. This value is low in comparison with values reported in chloroform solution for dialkyl ketones and benzophenone, i.e., 1.9 and 2.4' (22), respectively.1° In the case of planar chromophores, conjugation with an ethylenic double bond or aromatic ring brings about an increase in the carbonyl-stretching band intensity (20,22). While the positions of the carbonylstretching bands of 3, 6, and 12 show a considerably higher degree of conjugation than that in benzophenone, their intensities per carbonyl group are similar to, or less than, that of the carbonyl-stretching band of benzophenone.…”

IR.‐spektroskopische Untersuchungen in der Imidazol‐Reihe

“…Nun l a s t sich aber die C=O-Gruppe eines Ringes auch so beeinflussen, dass man eine Doppelbindung in die cr-B-Stellung einfuhrt. Der so entstandene neue Konjugationszustand ist dadurch gekennzeichnet, dass die C=O-F'requenz schon bei einer tieferen Wellenzahl auftritt [4]. Eine [ 5 ] .…”