This is comparable with the reduction of the benzene nucleus into hexamethylene, a substance of an aliphatic character.
Cluded that in compounds the benzene nucleus appears to be capable of existence in two tautomeric forms, in the sense that each particular derivative possesses a definite constitution.
The introduction of hydroxyl groups into the benzene nucleus gives rise to compounds generically named phenols, which, although resembling the aliphatic alcohols in their origin, differ from these substances in their increased chemical activity and acid nature.
Those with the hydroxyl group in the benzene nucleus are prepared from the aminophenols by the Skraup reaction.
These observations may be summarized by saying that the benzene nucleus is more negative in character than the aliphatic residues.
Soc. 61, p. 367): If the hydrogen compound of the substituent already in the benzene nucleus can be directly oxidized to the' corresponding hydroxyl compound, then meta-derivatives predominate on further substitution, if not, then orthoand paraderivatives.
The benzene nucleus presents a remarkable case, which must be considered in the formulation of any complete theory of valency.
Those substituted in the benzene nucleus are obtained by condensing two molecules of a substituted benzyl and benzal chlorides.