Reaction Mechanisms
Moderators: Chem_Mod, Chem_Admin
-
- Posts: 52
- Joined: Thu Jul 27, 2017 3:01 am
Reaction Mechanisms
What are the two methods of finding the Reaction Mechanisms, how can you tell them apart, and will we be applying both on the final? I faintly remember Professor mentioning something about excluding one method, or perhaps i misheard. However, can somebody clarify for me?
-
- Posts: 30
- Joined: Sat Jul 22, 2017 3:00 am
Re: Reaction Mechanisms
The two ways to find a reaction mechanism are:
1) direct computation with differential equations (we aren't doing this method)
2) identifying the rate-limiting step and comparing the rate law of the rate-determining step to the overall rate. There are 2 methods the textbook discusses: steady-state and pre-equilibrium. We have been using the pre-equilibrium method in lecture because it's simpler (but less flexible). This involves assuming the reaction before the rate-limiting step is at equilibrium, writing out the rate laws for each elementary step, using the equilibrium constant K expression to substitute for intermediates if necessary.
1) direct computation with differential equations (we aren't doing this method)
2) identifying the rate-limiting step and comparing the rate law of the rate-determining step to the overall rate. There are 2 methods the textbook discusses: steady-state and pre-equilibrium. We have been using the pre-equilibrium method in lecture because it's simpler (but less flexible). This involves assuming the reaction before the rate-limiting step is at equilibrium, writing out the rate laws for each elementary step, using the equilibrium constant K expression to substitute for intermediates if necessary.
-
- Posts: 54
- Joined: Thu Jul 27, 2017 3:00 am
Re: Reaction Mechanisms
1. Direct Computation by solving differential equations (won't need to know this)
2. Identify rate-limiting step. Use rate law of rate-limiting step as overall rate. Compare model w/ experiment.
a. Steady State Approximation: constant intermediate concentration in rate-limiting step (won't need to know this)
b. Pre-Equilibrium Approach: Reaction before rate-limiting step is at equilibrium, use its equilibrium constant K. (Know this!!)
i. Essentially this is the one where there's a fast step before the slow step which creates a bottleneck and a buildup of intermediate.
2. Identify rate-limiting step. Use rate law of rate-limiting step as overall rate. Compare model w/ experiment.
a. Steady State Approximation: constant intermediate concentration in rate-limiting step (won't need to know this)
b. Pre-Equilibrium Approach: Reaction before rate-limiting step is at equilibrium, use its equilibrium constant K. (Know this!!)
i. Essentially this is the one where there's a fast step before the slow step which creates a bottleneck and a buildup of intermediate.
Return to “Reaction Mechanisms, Reaction Profiles”
Who is online
Users browsing this forum: No registered users and 8 guests