Are These Two Reaction Mechanisms for the Same Reaction?

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Discussion Overview

The discussion revolves around two proposed reaction mechanisms for the same chemical reaction. Participants are tasked with determining whether the mechanisms are equivalent and which one is correct based on the provided rate expression and the characteristics of each mechanism. The scope includes theoretical analysis and rate law considerations in organic chemistry.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant suggests that both mechanisms are the same because they start with the same reactants and produce the same products, noting a difference in the rate of an elementary reaction.
  • Another participant emphasizes the need to find the net reaction by adding the parts of both mechanisms to prove they pertain to the same overall reaction.
  • A later reply indicates that both mechanisms cannot be correct simultaneously, pointing out that a valid mechanism must align with the rate equation provided.
  • Participants discuss the significance of the rate-determining step in determining the correctness of a mechanism, although specifics are not fully explored.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether both mechanisms can be correct. There is disagreement on how to determine the validity of each mechanism based on the rate equation and the concept of rate-determining steps.

Contextual Notes

Participants express uncertainty about the implications of the rate expression and how changes in concentration affect the mechanisms. There are unresolved questions regarding the criteria for determining the correctness of a reaction mechanism.

Who May Find This Useful

This discussion may be useful for students studying organic chemistry, particularly those interested in reaction mechanisms and kinetics.

OmiChem
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I'm given two reaction mechanisms, both are supposedly for the same reaction and I'm asked to prove it. The reaction mechanisms are:

#1

OCl- + H2O --> HOCl + OH- (medium speed)
HOCl + I- --> HOI + Cl- (slow)
HOI + OH- --> H2O + OI- (fast)

#2

OCl- + H2O --> HOCl + OH- (slow speed)
HOCl + I- --> ICl + OH- (medium)
ICl + 2OH- --> OI- + Cl- + H2O (fast)

I'm guessing that since the original reactants are the same for both and they both form OI- and water as a product, they are the same.. the only difference I can see is that the chlorine ion is separated in a different step, which causes a difference in the rate of that elementary reaction. Also, the rate expression for the final reaction: Rate = k[I-] SHOULD be right, but I'm not sure if it is.. I- seems to be the ion that affects the rate but I'm a little behind on my organic chem so I need some help...thx ahead of time
 
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You are required to prove that they pertain to the same overall reaction ?

In both cases, find the net reaction by simply adding the parts. What do you get ?
 
Oh, sorry, i should of explained more.. there are three parts to the question.. the first is to show that both are for the same reaction, I should of known that, sorry slipped my mind totally to use the net equation... wow lol. Other than that, I am given the rate expression and asked questions about changes such as tripling the I- concentration and such, i do not need help with that. It then proceeds to ask me which mechanism is correct. This i don't understand. How do i figure out which of the mechanisms is correct...if both are for the same reaction, aren't they both correct?
 
No, they won't both be correct. I can make up a bogus mechanism for the same reaction, and it would definitely be wrong. You determine the correct mechanism by looking at the rate equation. According the the opening post, Rate = k[I-] is the given rate equation.

What do you know about rate determining steps ?
 

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