4-Chlorophenol is an organic compound with the formula C<sub>6</sub>H<sub>4</sub>ClOH. It is one of three monochlorophenol isomers. It is a colorless or white solid that melts easily and exhibits significant solubility in water. Its pK<sub>a</sub> is 9.41.
It is prepared by chlorination of phenol, preferably in polar solvents, which tends to yield the 4-chloro derivative. Direct chlorination of molten phenol favors the formation of 2-chlorophenol.
It once was produced on a large scale as a precursor to hydroquinone. It is a classic precursor, upon reaction with phthalic anhydride, to quinizarin. The commercial dye quinizarin is produced by the reaction of phthalic anhydride and 4-chlorophenol followed by hydrolysis of the chloride.