Final answer:
The reaction between chlorobenzene and chloral produces DDT, which is harmful to the environment and has led to population declines in birds due to thinner eggshells and disruption of reproductive cycles.
Step-by-step explanation:
The product formed when chlorobenzene reacts with chloral to produce an insecticide harmful to fish, birds, and humans is DDT (dichloro, diphenyl, trichloroethane). DDT has been associated with environmental and health risks such as biomagnification, leading to thinning eggshells in birds like eagles and pelicans, ecological harm to fish and increased resistance to insects.
DDT was widely used to combat mosquitoes spreading malaria due to its persistence in the environment. However, its widespread use also resulted in significant environmental impacts, including biomagnification effects on top-of-the-food-chain predators, which presented serious reproductive challenges. The substance's harmful effects on wildlife prompted the United States to ban DDT in the 1970s after substantial declines in bird populations were observed.