Variants of the single-step processing of unfractionated crude phenols by phenol-formaldehyde or oxidative oligomerization and/or complexation with organic substrates have been proposed. These treatments result in a significant increase in the inhibitory activity of the phenols and elimination of processing drawbacks of these substrates, such as unpleasant organoleptic properties and high solubility in water, and foremost make it possible to engage coal tar phenols back in petrochemical processes as polymerization inhibitors.