ncert books class 12 chemistry chapter 6 · Section 1

The replacement of hydrogen atom(s) in an aliphatic or aromatic hydrocarbon by halogen atom(s) results in the formation of alkyl halide (haloalkane) and aryl halide (haloarene), respectively. Haloalkanes contain halogen atom(s) attached to the sp hybridised carbon atom of an alkyl group whereas haloarenes contain halogen atom(s) attached to sp hybridised carbon atom(s) of an aryl group. Many halogen containing organic compounds occur in nature and some of these are clinically useful. These classes of compounds find wide applications in industry as well as in day- to-day life. They are used as solvents for relatively non-polar compounds and as starting materials for the synthesis of wide range of organic compounds. Chlorine containing antibiotic, chloramphenicol, produced by microorganisms is very effective for the treatment of typhoid fever. Our body produces iodine containing hormone, thyroxine, the deficiency of which causes a disease called goiter . Synthetic halogen compounds, viz. chloroquine is used for the treatment of malaria; halothane is used as an anaesthetic during surgery. Certain fully fluorinated compounds are being considered as potential blood substitutes in surgery. In this Unit, you will study the important methods of preparation, physical and chemical properties and uses of organohalogen compounds. After studying this Unit, you will be able to · name haloalkanes and haloarenes according to the IUPAC system of nomenclature from their given structures; · describe the reactions involved in the preparation of haloalkanes and haloarenes and understand various reactions that they undergo; · correlate the structures of haloalkanes and haloarenes with various types of reactions; · use stereochemistry as a tool for understanding the reaction mechanism; · appreciate the applications of organo-metallic compounds; · highlight the environmental effects of polyhalogen compounds.