In this video, I want to focus on a specific type of condensation reaction called an aldol condensation. From prior videos, we know that an enolate is a negatively charged species and it can attack electrophiles. But what we didn't fully realize up until this point is that these enolates can actually react with themselves to condense. Specifically, if it's a ketone or aldehyde, it's going to condense into this category of molecule called a beta-hydroxy carbonyl. The final products are called aldols. That's the reason that we have that name because they're part aldehyde and they're part alcohol. Hence the name aldol. What I'm going to do here is I'm going to show you the full mechanism for an aldol condensation. One of the most important things to realize about any condensation reaction is that a big part of getting these questions right isn't just knowing the mechanism. It's knowing how to line up your carbonyls because if you line them up incorrectly, you're going to be doing a lot more work and you're probably going to get it wrong. I'm going to teach you not only just the mechanism but I'm going to use my years of teaching experience to try to engrain this method into you of how is the best way to line up your carbonyls so that you can always visualize the product the easiest. The first step guys is super easy. All it is is that you're using some kind of base, usually OH negative, to pull off a proton and make your enolate. Remember that enolates have two different resonance structures. There's also a resonance structure with the negative on the O but we're not going to use that one. For this mechanism, you always want to be using the enolate on the carbon because that's going to help predict what our product looks like. The reason that we would get an aldol condensation is when you have a base, but you have no other electrophile. I'd be wondering how would I know that something is an aldol and how would I know that something is let's say a reaction from another chapter because there's a lot of reagents that you know now. But guys, if you are forming an enolate without an electrophile to react with, then you know this is going to be a self-condensation, which is exactly what we're going to draw. We've got our enolate. Notice that my enolate, I'm drawing it on the left-hand side. I'm always going to draw the enolate on the left. I don't have an electrophile on the right. I don't have a halide or an acyl chloride, whatever. That means I'm forced to react with just another carbonyl. How does that work? I like to call them; there's the enolate and there's the electrophile. Why? The enolate is the one with the negative charge. The electrophile is the one that you're going to attack the partial positive of. This one should not be in an enolate form. You should just draw this the normal way that it was before the base reacted. A few other pointers here. You want to make sure that your enolate is drawn on the left, but that your anion is toward the electrophile because you want to have the electrophile and the anion as close to each other as possible. Here, I'm drawing the enolate on the left but I want to make sure my negative charge is as close to the electrophile as possible. Also, any R groups on it face downwards. This is going to come up more later. But if I had bulky R groups on that CH2, I should actually face them facing down to clear the way for the electrophile that I'm about to attack. My electrophile, you've actually got some special rules about that one. The electrophile you draw on the right. Always draw on the right and you should draw your smallest group toward anion. The reason is because we're going to have to attack with the anion and it's going to be easiest to visualize if I have my small group close to the anion and my large group away from it. I think that's enough to get going. This mechanism is going to look like follows. This is a nucleophilic addition mechanism. My negative charge is going to attack my partial positive. I'm going to break a bond and I'm going to make a tetrahedral intermediate. It's a big tetrahedral intermediate. I understand. But you still have an O negative with now what groups? Now you've got the extra CH2 that's attached here. We still have that H. The H that was here is still here. It's just I'm not drawing it. Then there's the CH3. This is called a nucleophilic addition mechanism because we're going to protonate the O at the end. We're not going to kick out a leaving group. We use water or acid to protonate and to give us our beta-hydroxycarbonyl because I have a beta-hydroxy on my carbonyl. The reason I call it carbonyl is because it could be either a ketone or an aldehyde, just depending on what you started with. That's really it. It's a really easy mechanism. It's nuc...