 Alright, welcome back everybody. More organic chemistry. This is also, hopefully, a relatively simple video where you're going to talk about alkene molecules and how it's possible to alter alkenes. I'm not going to expect you to know much, so don't get bogged down in the details, but focus on what I say to focus on. If you remember, a molecule with an alkene functional group is a molecule that has two carbons double bonded to each other. I'm going to talk about a bunch of different kinds of chemical reactions that are usually called addition reactions, and I will explain why they're called addition reactions right here. So if you remember, carbon atoms have to make four covalent bonds in organic molecules, so this carbon here currently is making two. So there must be two other bonds, and so let's just pretend that there's something in spot number one and spot number two over there on the carbon on the left. Same thing with the carbon on the right. There's something in position number three, and there's something in position number four, and this is just a generic molecule with an alkene functional group. Now imagine that I could somehow work some magic and take that double bond and break it and turn it into a carbon-carbon single bond. If I could do that, well, there's still going to be something stuck to positions one, two, three, and four. But this carbon needs a fourth attachment, right? It needs a fourth bond, so there's some mystery thing that I would have to attach there if I broke this double bond and turned it into a single bond. I'd have to add something there, and I would also have to add something to the carbon on the right side. And if I do this kind of reaction, if I bust this double bond, turn it into a single covalent bond, and I add two more things on the left and the right, that is called an addition reaction, because I'm adding things to those carbons. And there are a bunch of different addition reactions. I'm not going to expect you to memorize the specifics of how they work, but I'm just going to ask you to be able to recognize them based on their names. Here are their names. The first one is called a hydrogenation reaction. Halogenation is the second one, and hydration is the third one. These are all examples of addition reactions, and we're going to explain each one in just a tiny bit of detail on the following slides. Hydrogenation reaction means that you bust that carbon-carbon double bond, and you add hydrogens. That's what hydrogenation means. Here is my pretend molecule with a double bond. I add H2. You don't need to know any of this. All you need to know is this double bond turns into a single bond, and these Hs, they get stuck onto those carbons. They didn't used to be there over here. They are there now. They're stuck on. This is an example of a hydrogenation reaction. So I want you to know what hydrogenation means. Don't worry about any of this stuff here, but if you see a reaction where something has a carbon-carbon double bond, it turns into a carbon-carbon single bond, and hydrogen's got stuck on, well, that's a hydrogenation reaction. If you have ever heard of partially hydrogenated vegetable oil, the hydrogenated here means the same thing as hydrogenation. In other words, vegetable oil must have some carbon-carbon double bonds, and if they partially hydrogenate the vegetable oil, that means they convert some of the carbon-carbon double bonds into single bonds and end up adding hydrogens to the vegetable oil, but they only do it partially. They only do it to some of the double bonds. I don't know what that does to the vegetable oil. I think it makes it last longer, maybe taste a little better, not sure, but that's where that word comes from. So this is one example of an addition reaction. The next kind of addition reaction is called halogenation. These atoms here, they are in the 17th column of the periodic table. This one is unstable. You're never really going to see that one. These others, they are called halogens. If you break a carbon-carbon double bond and you end up putting any of these kinds of atoms onto the carbons, that is called a halogenation reaction, and that is just another example of an addition reaction. Again, I don't really care about the details here, the names, all that stuff. If you see a molecule with a carbon-carbon double bond and it's converted into a carbon-carbon single bond and one of these kinds of atoms ends up stuck to those carbons, then that's a halogenation reaction. The last addition reaction that I'm going to talk about is called a hydration reaction. You've probably heard the word hydration before, that means adding water to something and that is what happens with a hydration reaction here. Here we have our carbon-carbon double bond. This is water, right, H2O. Don't worry about that. The weird thing about the hydration reaction is if you break this double bond and turn it into a single bond and you add pieces of water to those carbons, you add a hydrogen to one carbon and you add an OH to the other carbon, you end up making an alcohol functional group. So hydration reaction, interestingly enough, ends up making a molecule with an alcohol functional group. Again, don't worry about this. So what do I want you to know? Don't memorize the specifics about the addition reactions, but you should know what an addition reaction is. You should be able to recognize and know what hydrogenation means. You should be able to recognize and know what halogenation means. You should recognize and know what hydration means. And that's the end of this video.