So let's go ahead and look at this example here. Here I have 2 acids. Okay. So we're going to go ahead and draw some electron clouds in order to figure this out. But first of all, I just want to ask you guys, if you didn't know about this trend, could you solve this question with pKa's? Which one is the stronger acid? Could you solve it with pKa's? Actually, no, you couldn't because we said the pKa of alcohol is roughly 16. So this one is 16 and this is also an alcohol at 16. So according to my pKa rules, I cannot tell the difference of which one's more acidic and which one's less acidic. Alright? So this is one of those examples where my pKa's are too similar to tell the difference, so I'm going to need to use a factor affecting acidity.
Now check this out. Both of these have the same exact element effect because in both cases, I have an oxygen attached directly to the H. So is the element effect going to be different at all? No. They're the same. The electronegativity is the same and the size is the same because they're both oxygen. Okay? But what is different about these is that one of these has 3 fluorines really far away and then one of these has 2 fluorines really close. So let's see how that's going to affect it.
This is the part that I was talking about: electronegative things that are on other parts of the molecule will affect the H. So what I want to do is give away an H. Give away an H and what we're going to get now is the conjugate bases. Let's look at the conjugate bases. The conjugate bases look like this. Basically, a negative charge in the O here and a negative charge in the O here. The only difference is that when I draw, like if you want if I want to draw like an electron cloud of where those electrons are, for the O on the left-hand side, it would just look like this. Pretty much all those electrons would reside just on that O, meaning that these are localized.
But then check this one out over here. This one has these 2 very electronegative atoms right next to it. So what that means is that instead of all the electrons being around the O, some of them are going to get spread out over these fluorines. Okay? So what that means is that I'm going to have less of a charge around my O and I'm going to have a little bit more of a charge in other parts of the molecule. In fact, if I were to draw this again, I'd probably make this part around the O even a little bit smaller. It would probably look more like this, like more spread out like that.
Okay? Now you're never going to be asked to draw this. This is just my example. I'm just trying to get you guys to see how one of the conjugate bases is going to look different. But if you had to guess which of these conjugate bases is more stable, it would be the one on the right. It would be this one because this one is delocalized or spread out. Okay? So what that means is that if one of these acids, if both of these acids had the same opportunity to give up a proton, the one that would say, oh, me first me first would be the one on the right. Why? Because that's going to be the one that forms the more stable conjugate base right here. Whereas the other conjugate base, that one kind of sucks because it's all just in one place. Does that make sense, guys? Cool.