CBSE Class 12-science Answered
Halogenation involves the introduction of one or more halogen atoms (i.e. fluorine, chlorine, bromine or iodine) in the reactants. These reactants may be organic or inorganic species. The introduction of halogen atom(s) can be brought about by both substitution reaction as well as addition reaction. For example:
H2C=CH2 + Cl2 ? ClH2C-CH2Cl |
take example of chlorination
1. Initiation: chlorin gives chlorin free radical by passing U.V. light
Cl-Cl gives Cl. +Cl.
2. Propagation: chlorin free radical abstracts hydrogen from methane gives methyl free radical
Cl. +CH4 gives .CH3 +HCl
Methyl free radical gives methyl chloride and chlorine free radical
CH3 . + Cl2 gives CH3Cl + Cl.
3. Termination: in this step all reactions are consumed and get terminated
Cl. +Cl. gives Cl2
CH3 . + CH3 . gives C2H6
CH3 . + Cl. gives CH3Cl
Remember: free radicals have dots (.) at superscript.