Initiation:

$I\stackrel{K_d}{\to }2R$

$R+M\stackrel{K_i}{\to }{P}_1$

Propagation:

$P_n+M\stackrel{K_p}{\to }{P}_{n+1}$

Termination (disproportionation only):

$P_n+P_m\stackrel{K_{td}}{\to }{D}_n+D_m$