4-Chloroaniline (4-ClA) is a chlorinated aromatic amine that is formed as an intermediate during the microbial decomposition of phenylurea and phenylcarbamate. The formation of various oligomers by polymerization of 4-ClA with guaiacol in an aqueous solution containing oxidoreductases has been reported. 4-ClA undergoes decomposition via oxidation by fusarium oxysporum, a soil fungus.