 Here's a molecule of ethanol and here's a molecule of methanol. If I tell you that I can compare the acidic strength of this molecule and this molecule just by looking at its structure, would it be really cool? In this video, we'll learn how to compare the acidic strength of organic acids without any data. Let's start from the beginning. Any organic acid should look like this, HA. It dissociates into H plus and A negative. This A negative is called our conjugate base and this could be anything. This could be an atom, a molecule, a group of atoms in a group of molecules. But the idea of an acid is that it will always dissociate to give us H plus and A negative. There used to be a question in my head that why does this HA even dissociate to give us H plus and A negative? We'll not go too deep into it, but there are two reasons. First that the HA bond is not that strong, right? And the other is that the resulting A negative is stable. So from here, we can guess for an organic molecule to be a good acid, it should give us H plus and A negative easily, right? In this video, we'll be talking about the stability of the conjugate base. If a conjugate base is stable, the organic molecule is a good acid. The goal of this video is to A, learn how to write the conjugate base and B is how to compare the stability of these conjugate bases. When you first start doing these problems, you realize that you were told with an example of HA that a molecule like HA will dissociate into H plus and A negative. But in the examples that we have in our hands like CH3, CH2, OH, we have six hydrogens. Which hydrogen will it lose first? Or in other words, which is the most acidic hydrogen? To understand which is the acidic hydrogen, let me draw this structure a little differently. Let me show you that there are CH3, CH and OH. The idea is that I want to draw two different kinds of hydrogens that exist in this molecule. One is where the H is connected to oxygen and the second is when the H is connected to carbon. The first thing that I can see here is that oxygen is highly, highly electronegative which pulls the electron cloud towards itself. So it will create a partial negative charge. As a result, hydrogen will create a partial positive charge. Because ethanol and methanol are in solution, they interact with neighboring water molecules. As in the case of this kind of bond, oxygen here as well develops a negative charge and hydrogen here also develops a partial positive charge. Without going too much into detail, because it's not important for us right now, we see that hydrogen here breaks off easily and creates a bond with this neighboring water molecule. This reaction gives us something like this. And this molecule is the conjugate base of ethanol which we'll call ethoxide. Next order of business is to compare the stability of ethoxide and the conjugate base of methanol. I want you guys to pause the video and think for a second, how will you make the conjugate base of methanol? As in the case of ethanol, we end up with something like this and in the case of methanol, if you guys made something similar to ethanol, good job, you get the idea of acidic hydrogen. And from here, there's only one step and arguably the most important step of such kind of problems. We need to compare the stability of this molecule with this molecule. How can we do that? How do we compare the stability of this molecule with that molecule? We take the help of something called electronic effects. As we learned before, to stabilize anions, we need aromaticity which provide the maximum stabilization. Right after aromaticity, we have resonance and right after resonance, we have inductive effect. Now that we have a checklist, we'll be going in this direction to see if there is aromaticity, resonance and inductive effect in both these molecules. Let's look at ethoxide. CH3, CH2, O negative and we have CH3 and O negative. As there are no double bonds, there is no scope of aromaticity and resonance. We can see that there are alcohol groups attached to oxygen, so there is some kind of inductive effect going on here. Because carbon is less electronegative than oxygen, the electron cloud on this alkyl group will be sucked by oxygen. We call it electron donating group. We can go further and say that the electron cloud on carbon was more concentrated because it's way more electronegative than hydrogen and it can suck hydrogen's electron cloud. The same way, oxygen is electronegative enough that it can pull this methyl's electron cloud as well but not as much. In the same way, this methyl group also donates its electron cloud towards oxygen. In previous videos, we have discussed how electron donating groups destabilize anions but as a quick recap, let me tell you. Oxygen is highly electronegative. It can suck up the electron clouds from over the alkyl groups but it's really small that it cannot accommodate all these charge. That means that this electronic effect destabilizes the conjugate base. Because inductive effect is present on both the sides, we should go ahead and check which molecule is more destabilized than the other. My hunch is that because there is an extra methyl group which donates extra electron clouds towards oxygen, it is more destabilized than this molecule where only one methyl group is donating its electron cloud. Because ethoxide is less stable than methoxide, it's safe to say that ethanol is a weaker acid than methanol.