Substitution reactions of Alkanes

Halogenation

 Halogenation 
 Introduction of halogen group in alkane is called halogenations. It is a substitution reaction. 
 Or 
 Replace the hydrogen with halogen in alkanes is called halogenation.
 It is a free radical mechanism. The halogenation of alkanes involves in three steps 
 Initiation 
 Propagation
 Termination
 Initiation
 Cl___Cl »»»»»» Cl° + Cl
 Propagation 
 C°H3+ Cl2»»»»»CH3Cl + Cl°
 CH3---Cl+Cl°»»»»»C°H2Cl+HCl
 Termination
 C°H2Cl +Cl2»»»»» CHCl2 + HCl

 Mechanism 

 CH4+Cl2»»»»CH3Cl+HCl 
 CH3Cl+Cl2»»»CH2Cl2+HCl
 CH2Cl2+Cl2»»»»CHCl3+HCl 
CH3Cl3+Cl2»»»»CCl4+HCl 
 Similarly

 Bromination 

 Substitution of hydrogen by bromine is called bromination.
 Or Introduction of bromine group in alkanes is called halogenation or bromination .
 It is a free radical mechanism. The halogenation of alkanes involves in three steps
 Initiation 
 Propagation 
Termination 
 Initiation 
 Br___Br »»»»»» Br + Br 
 Propagation
 C°H3+ Br2»»»»»CH3Br + Br
 CH3Br+Br»»»»»CH2Br+HBr 
 Termination
 CH2Br +Br2»»»»» CHBr2 + HCl

 Mechanism 

 CH4+Br2»»»»CH3Br+HBr 
 CH3Br+Br2»»»CH2Br2+HBr
 CH2Br2+Br2»»»»CHCl3+HBr
 CH3Br3+Br2»»»»CBr4+HBr