- Concept Videos
- Solutions 16

What best describes the species at the rate-determining transition state?

Hey guys. So, in this question it wants to know what does describes the species at the rate determining transition state, so what we're talking about is if we go up to our reaction, the stuff it's talking about is right here, okay?. Remember, that the top of our graph is going to be our transition state and then at three we have our first intermediate, so remember that our intermediate is going to be this carbocation, okay? in this elimination reaction. So, what we need to know is what comes before that. So, our transition state and it's going to be some partial bonds in that, so if we scroll down, remember we're starting off with something that looks like this, we have carbons all around and then we have a bromine, right? if we scroll up, these are all methyl groups CH3, CH3 and CH3 and what we need to get to is a species that looks like this, where now we just have a carbon with these CH3's, right? But we no longer have that bromine on it, so this carbon actually has a partial, this positive charge, right? Is that carbocation, so the transition state is going to be what happens in between them we need to show it's actually occurring, which is this bromine actually leaving. So, that transition state is going to be where we have this regular carbon here, these methyl groups and we're going to show a partial bond to our bromine, okay? It's going to be negative because it's going to be broken off as this bromide ion, okay? With a negative charge, so we can show that and then of course we can show this partial positive charge here, okay? So this is going to represent our first transition state. So, do you see this anywhere in our questions or in our answer choices? Well, it's not DNC that's showing a lot occurring at one time, right? So we can cross those out, what B is showing is our intermediate, right? this structure without the bromine, just this, but we know we're looking for that transition state that's very high in energy, so this in green is going to be represented at our transition state where we have a partial bond showing our bromine in the process of leaving, okay? So I hope this makes sense on how our answer choice is A. Alright, so now let's take a look at the next problem.