question_answer 103)

  What are the IUPAC names of the insecticide DDT and benzene hexachloride ? Why is their use banned in India and other countries ?

Answer:

                  Both elimination reactions (particularly -elimination reactions) and nucleophilic substitution reactions occur simultaneously. However, by a proper choice of reagents and reaction conditions, we can make one reaction to predominate over the other. Usually strong and bulkier bases and high temperature favour elimination reactions whereas weaker and smaller bases and lower temperature favour substitution reactions. For example, ethyl bromide on heating with alcoholic KOH (which contains the stronger base  ion) about 473-523 K undergoes elimination to give ethene while with aqueous KOH at about 373 K it gives  ethanol.                For further details refer to 'Supplement your knowledge' pages 10/38-10/40.