A new technique was recently introduced into humic acid chemistry. This involved reaction with phenol leading to depolymerization, and the replacement of aromatic groups by phenol with the formation of relatively simple compounds. These were considered to be characteristic of the linkages joining the aromatic groups together. There is the possibility that reactive groups, other than aromatic ones, could be responsible for the reaction. In this study, reaction of phenol with a range of model compounds is examined so that a further evaluation may be made of the usefulness of phenol depolymerization and to indicate some of the possible side reactions. It is concluded that the overall side reactions are minor and do not invalidate previous conclusions that the phenol depolymerization reaction is useful for the study of humic acid.