Question

Question 13.1 How do you account for the formation of ethane during chlorination of methane?

Class XI Hydrocarbons Page 396

Answer 1

mechanism of chlorination of methane is proceed in three steps :
step 1 :-
initiation :- Cl ____Cl --(hv, homolysis ) ---> Cl• + Cl• {chlorine free radicals }

propagation :-
(a) CH4 + Cl• -----(hv)----> CH3• + H---Cl
(b) CH3• + Cl___Cl ---(hv)----> CH3--Cl + Cl•

Termination :-
(a) Cl• + Cl• ------> Cl---Cl
(b) H3C• + CH3• ----> CH3---CH3
(c) H3C• + Cl• -----> H3C--Cl {chloro methane}

from the above mechanism, it is clear that methyl free radicals are produced during propagation step . in termination step(b), two methyl free radicals combined with each other and formed a molecule of ethane.