CHLOROPHENOL

any of a group of toxic, colourless, weakly acidic organic compounds in which one or more of the hydrogen atoms attached to the benzene ring of phenol have been replaced by chlorine atoms; 2-chlorophenol is a liquid at room temperature, but all the other chlorophenols are solids. The most generally useful property of the chlorinated phenols is their toxicity to various organisms: they and compounds made from them are used to control bacteria, fungi, insects, and weeds. Many members of the group are manufactured by treating phenol with chlorine; a few are made by hydrolysis of polychlorobenzenes. The compound 4-chlorophenol is a starting material for making 2-benzyl-4-chlorophenol, a germicide; it can also be converted to acetophenetidin, an analgesic. Formaldehyde reacts with 2,4-dichlorophenol to form methylenebis(dichlorophenol), used as a mothproofing agent, an antiseptic, and a seed disinfectant; 2,4-dichlorophenol, with chloroacetic acid, forms 2,4-dichlorophenoxyacetic acid (2,4-D), a weed killer. Of the trichlorophenols, the 2,4,6-isomer is used as a bactericide and fungicide. The 2,4,5-isomer has similar applications and also can be converted to methylenebis(trichlorophenol), or hexachlorophene, or into thiobis(trichlorophenol), both used as germicides in soap; into dimethyl trichlorophenyl phosphorothioate, a systemic agent effective against grubs in cattle; and into 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) or 2,4,5-trichlorophenoxypropionic acid (2,4,5-TCPPA), both widely used as weed killers. Tetrachlorophenol is an insecticide and a bactericide and is used as a preservative for latex, wood, and leather. Pentachlorophenol (penta) is a disinfectant, a fungicide, and an extremely effective preservative for wood.