In the preceding paper of this series, refractive indices and molecular extinction coefficients over a wide range of wave-lengths were recorded for the two cyclic hydrocarbons
cyclohexene
and 1:3-
cyclohexadiene
. These observations completed a study of the refractive dispersions of the series of 6-ring compounds C
6
H
12
, C
6
H
10
, C
6
H
8
, C
6
H
6
; they also provided a basis for the study of the phenomenon of "optical exaltation," which is exhibited by compounds containing conjugated double bonds, since the last two members of the series belong to this type. Conjugation, however, may be effected, not only between two olefinic double bonds, but also between an olefinic double bond and an oxygenated radical, such as the carboxyl, carbonyl, or hydroxyl group. The present paper, therefore, records the absorption spectra and refractive dispersions of three oxygenated derivated of cyclohexane, namely,
cyclohexanol
,
cyclohexanone
, and
ethyl hexahydrobenzoate
, in the molecules of which each of the preceding groups is exemplified. Dispersion curves are thus now available for typical compounds of the cyclohexane series containing "unsaturated" radicals of all the principal types which are used in constructing conjugated systems, and the way has been prepared for a detailed study of conjugation, as exemplified on the one hand by
cyclo
hexadiene, and similar compounds containing two olefinic radicals, and on the other hand by a variety of compounds containing a double bond in addition to a hydroxyl, carbonyl, or carboxyl group. It is anticipated that, with the help of the date set out in the preceding and present papers, it will be possible in a later communication to demonstrate in what respect the behaviour of conjugated compounds differs from that which might be anticipated from a merely additive behaviour of the chromophoric radicals, and thus to determine the nature, and if possible to discover the origin, of the phenomenon of optical exaltation.
Refractive dispersion of organic compounds. V-Oxygenated derivatives of cyclohexane the inadequacy of the Ketteler-Helmholtz equation