Question

Which is rate determining step of chain initiation step?

• A. Chain propogation
• B. Chain initiation
• C. Initiator decomposition
• D. None of the above

Answer 1

The correct option is C Initiator decomposition

Chain propogation is not a chain initiation step. Chain initiation step includes decomposition of initiator followed by the addition of radical with monomer. Out of these, decomposition of initiator is the slowest step and rate determining step.

Example:
Chain initiation
$I\stackrel{\mathrm{Heat}}{\to }2I^{.}\mathrm{Decomposition}\mathrm{of}\mathrm{initiator}\left(\mathrm{slow}\right)I^{.}+M\to M^{.}\mathrm{Formation}\mathrm{of}\mathrm{monomer}\mathrm{radical}\left(\mathrm{fast}\right)$