A research team is investigating the decomposition of methyl tert-butyl ether (MTBE) in the presence of bromine monoxide, BrO(g). Kinetic experiments suggest that BrO acts catalytically through the following proposed elementary steps (all species are in the gas phase):
Step 1 BrO + MTBE → Br + (CH₃)₃CO• slow
Step 2 Br + O₂ → BrO + O• fast
Step 3 O• + (CH₃)₃CO• → 2 (CH₃)₂CO + H₂O fast
Overall reaction: MTBE + O₂ → 2 (CH₃)₂CO + H₂O
Assume that the mechanism above is valid and that no other elementary steps occur.
(a) Identify every species in the mechanism as either (i) a catalyst, (ii) an intermediate, or (iii) neither. Provide a brief justification for each classification based solely on the sequence of elementary steps.
(b) Using your classifications from part (a), explain why the net concentration of BrO remains effectively constant during the course of the reaction, even though it appears in the slow step.
(c) If the concentration of BrO is doubled while all other initial concentrations are held constant, the experimentally determined initial rate also doubles. Explain how this observation is consistent with the elementary-step sequence given above.
(d) The research group proposes adding molecular bromine, Br₂(g), instead of BrO(g) to the reaction mixture. Predict whether Br₂ would function as a catalyst under the same conditions and justify your answer in terms of how, or whether, it would be regenerated.