Question

In the halogenation of alkanes other than methane, there is another chain-terminating reaction called disproportionation. Write the mechanism of this reaction for $C_2{H}_6$

Answer 1

Mechanism for chlorination of ethane:

Chain Initiation Step: $C{l}_2\stackrel{h\nu }{\to }2C{l}^{\ast }$

Chain Propagation Step: ${C{H}_3-C{H}_3+C{l}^{\ast }\to C{H}_3-C{H}_2}^{\ast }+HCl$

Chain Termination Step: 1) ${C{H}_3-C{H}_2}^{\ast }+{Cl}^{\ast }\to C{H}_3-C{H}_{2}Cl$

2) ${C{H}_3-C{H}_2}^{\ast }+C{l}^{\ast }\to C{H}_2=C{H}_2+HCl$ {Disproportionation Reaction}