RESEARCHES ON HYDANTOINS. XXIX. GEOMETRICAL ISOMERISM IN THE HYDANTOIN SERIES
Journal of the American Chemical Society
It appears established that azulene is closely related to the sesquiterpenes. From no other class of compounds have hydrocarbons been obtained which show such intense color. Colored hydrocarbons which have so far been prepared, are characterized by complex structure or a dense arrangement of the atoms, the intensity of the color increasing with the size of the molecule; for example: y 4 ) c : .( CsH4 I CH = CH)C<C6Hs2 C6H4 C6H4 CsHs )C:CHr; . 3. Deep red solid. Rubicen, a red hydrocarbon,
... hydrocarbon, C2BH14, m. p. 3 0 6 O .~ It is obvious that in azulene we have an entirely different and unique chemical compound. We hope, in a subsequent communication, to collect further data on this interesting substance. The writer wishes here to acknowledge his indebtedness to Dr. Francis D. Dodge for helpful suggestions as well as for aid in obtaining material used in connection with the above work. In order that geometrical isomerism may be shown in an unsaturated carbon compound, two fundamental conditions must be fulfilled : first, that the molecule contains a double bond between two of its carbon atoms, and second, that the two radicals linked to each of these two carbon atoms must be different. Theoretically, the accepted, structural formula of an aldehyde-hydantoin condensation product (I) fulfills both these conditions and consequently a hydantoin of this type might be expected to occur in cis-and trans-modifications. The constitutions of such isomeric forms might be expressed by the two graphic Formulas I1 and 111, respectively. Several unsaturated compounds of this type (I) have been prepared in this laboratory, but hitherto we have not detected the occurrence of more than one modification. In this paper we will now discuss the first case of this type of isomerism so far observed in the hydantoin series.