A process for preparing halongenated derivatives of benzonitrile by a direct vapor phase reaction of a halogen and benzonitrile in an open tube. Halogenated benzonitriles are useful as fungicides.
An aromatic compound of the class of phthalic anhydride and ortho-phthalonitrile can be monochlorinated, predominantly in the 4-position, by a vapor phase reaction involving passing chlorine and the aromatic compound through a heated zone maintained at a temperature above 350.degree. C.
