Hey, everyone. So in this example, it says, arrange the following compounds in order of increasing acidity, from weakest acid to highest acid. If we take a look here, we would say that we have a pyridine here, and here is its benzylic carbon. We know, because of resonance and induction, that this benzylic carbon is even more acidic than a typical benzylic carbanion.

So, we know that this is going to be the most acidic. So we're going to say b is most acidic, and let's figure out what the other ones would be. c should be the least acidic because, in c, we don't even have a benzylic position to deal with. So that's going to be even less. Right.

Next, remember, we're trying to deprotonate the benzylic position to make a carbanion. Here, it's harder to make that carbanion if you're already double bonded. It'd be kind of a weird situation. So a would be next. d would be the next acidic because, yes, we have a benzylic position here.

We could make a negative charge here that could resonate. But again, it's not as great acid-wise as b because the presence of the nitrogen means that we can resonate towards that more electronegative nitrogen. Through induction, it's better able to hold on to that negative charge. So in order of weakest to strongest acid, it would be c, a, then d, and then b being the strongest.