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 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. , a drug for controlling the high cholesterol and
triacylglyceride level in the blood, is derived from 4-chlorophenol. ==References==