Question

Give the preparation and uses of DDT.

Answer 1

Hint: Think about the full form of DDT (dichlorodiphenyltrichloroethane). This will show you what the components of DDT are and give you a hint as to how it may be prepared, the reagent that is used is concentrated sulphuric acid.

Complete Solution :
The structure of DDT is:

DDT is prepared by heating chlorobenzene and chloral in the ratio of 2:1 in the presence of concentrated sulphuric acid.
- The reaction goes as follows:

- Here, we can see that 2 moles of chlorobenzene combines with 1 mole of chloral on heating in the presence of concentrated sulphuric acid to give is dichlorodiphenyltrichloroethane i.e. DDT.
- There are many uses of DDT, especially as an insecticide and pesticide. Initially, during WWII it was also used to control illnesses like typhus, body lice, and malaria. This shows that DDT is basically an insect and mosquito repellent as it was used to combat insect borne diseases. It was also used to control the bubonic plague.
- In areas that had such epidemics, an airplane that flew over the region and sprayed large quantities of DDT in the surrounding area.

Additional Information:
DDT is now banned due to high levels of toxicity and deaths of people due to high dosage. It is bio-accumulative and the quantity magnifies as we go higher up in the food chain. A result of this was a sudden drop in the number of vultures that fed on dead carcasses of animals. This severely upset the food chain and the consequences can still be seen.

Note: Do not get confused while drawing the structure of DDT, it is a geminal compound with 2 bulky benzyl chloride groups on one carbon and only chlorine groups on the other. Remember the IUPAC name of DDT if the common name is too confusing 1,1'-(2,2,2-trichloroethane-1,1-diyl)bis(4-chlorobenzene). But memorizing the structure and then formulating the IUPAC name is easier.