Question

Which step is chain propagation step in the following mechanism?

• A. $(i)$
• B. $(ii)$
• C. $(iii)$
• D. $(iv)$

Answer 1

Answer: (B)

Elementary steps in which the number of free radicals consumed is equal to the number of free radicals generated are called chain propagation steps.
(i): Free radicals consumed - o; Free radicals generated -2
(ii): Free radicals consumed - 1; Free radicals generated - 1
(iii): Free radicals consumed - 2; Free radicals generated - o
(iv): Free radicals consumed - 2; Free radicals generated - o
Thus, (ii) is a chain propagation step.