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

(N/A) The chlorination of methane proceeds via a free radical chain mechanism,which involves three main steps: initiation,propagation,and termination.
$1$. Initiation: The reaction begins with the homolytic cleavage of the $Cl-Cl$ bond in the presence of light $(hv)$ or heat to produce chlorine free radicals:
$Cl-Cl \xrightarrow{hv} 2\dot{C}l$
$2$. Propagation: The chlorine free radical abstracts a hydrogen atom from methane to form a methyl free radical $(dot{C}H_3)$:
$CH_4 + \dot{C}l \rightarrow \dot{C}H_3 + HCl$
The methyl free radical then reacts with another $Cl_2$ molecule to form chloromethane $(CH_3Cl)$ and regenerate a chlorine free radical:
$\dot{C}H_3 + Cl-Cl \rightarrow CH_3Cl + \dot{C}l$
$3$. Termination: The reaction chain is terminated when two free radicals combine. The formation of ethane $(CH_3-CH_3)$ occurs when two methyl free radicals collide and combine:
$\dot{C}H_3 + \dot{C}H_3 \rightarrow CH_3-CH_3$