Chlorophenylacetonitrile is a yellowish liquid that is used as a grain fumigant. Also known as Chloro (4-chloropheyl) acetonitrile or 4-Chlorophenylacetonitrile, its molecular formula is C8H5Cl2N. Another synonym for it is 4-Chlorobenzyl cyanide. 4-Chlorophenylacetonitrile is a nitrile (acetonitrile) in which one of the nitrile's hydrogen molecules has been replaced with a p-cholorphenyl group. An acylacetonitrilase is an enzyme used to catalize a chemical reaction. One of this enzyme's substratas is 4- Chlorophenylacetonitrile, of the hydrolases family. Instead of acting on peptide bonds, it acts on carbon-nitrogen ones, specifically the ones in nitriles. Acetonitrile itself is important for use in medical research. Chlorophenylacetonitrile is toxic when swallowed, inhaled or comes in contact with skin. It must be kept tightly sealed after opening and in a cool, well-ventilated area. According to present data, it is not a known carcinogen.