Materials in this group are combustible. Some nitro and diazo derivatives of phenols explode when heated.

Compounds in this group do not behave as organic alcohols, as one might guess from the presence of a hydroxyl (-OH) group in their structure. Instead, they react as weak organic acids. Phenols and cresols are much weaker as acids than common carboxylic acids (phenol has pKa = 9.88). These materials are incompatible with strong reducing agents such as hydrides, nitrides, alkali metals, and inorganic sulfides. Flammable gas (H2) is often generated, and the heat of the reaction may ignite the gas. Heat is also generated by the acid-base reaction between phenols and bases. Such heating may initiate polymerization of the organic compound. Phenols are sulfonated very readily (for example, by concentrated sulfuric acid at room temperature). The reactions generate heat. Phenols are also nitrated very rapidly, even by dilute nitric acid. Nitrated phenols often explode when heated. Many of them form metal salts that can be detonated even by rather mild shock.

Ranges from moderate to high toxicity. Some of the more toxic members of this class of compounds are the chlorinated and nitro-substituted phenols that are used as pesticides and antibacterials (dinoseb, creosote, chlorinated phenol, p-nitrophenol). Phenol is strongly irritating to the skin.

Characterized by -OH on aromatic ring. Phenols are used in many organic syntheses, and the making of phenol/formaldehyde resins and polycarbonate resins.

Phenol, cresol, dinitrophenol, phenylphenol, dinitrocresol, alkyl phenol, aminochlorophenol, aminophenol, amyl phenol, butyl phenol, catechol, creosote, picric acid, resorcinol, trichlorophenol, dichlorocresol.