(A) Preparation: $DDT$ is prepared by the reaction of chloral with chlorobenzene in the presence of concentrated sulfuric acid.
$(b)$ Discovery: It is the first chlorinated organic insecticide. It was originally prepared in $1873$,and its effectiveness as an insecticide was discovered by Paul $M$üller of Geigy Pharmaceuticals in Switzerland in $1939$. Paul $M$üller was awarded the Nobel Prize in Medicine and Physiology in $1948$ for this discovery.
$(c)$ Properties: $(i)$ $DDT$ is a white solid. $(ii)$ It has a strong chlorine odor and causes eye irritation. $(iii)$ Ingestion may lead to cancer.
$(d)$ Uses: It was and is highly useful as an insecticide. It was effective in destroying mosquitoes that spread malaria and lice that spread typhus. Consequently,its use became widespread globally after World War $II$.
$(e)$ Problems and Disadvantages: Problems emerged in the late $1940$s due to excessive use. Many insect species developed resistance to $DDT$,and it proved highly toxic to fish. The problem was compounded by its chemical stability and fat solubility. $DDT$ is not metabolized rapidly; instead,it accumulates in fatty tissues. If ingestion continues,its concentration increases over time. The United States banned its use in $1973$,although it is still used in many parts of the world.