Now that we know how to name double bonds, there's an extra complication that we have to consider, which is that double bonds, because of the lack of free rotation, are going to be able to arrange themselves in different ways. So now we have to take into account not only the fact that there's a double bond, it has priority. We're also gonna have to take into account the arrangement of that double bond. So let's go ahead and get started. So I'm sure you've heard of the word CIS and trans before CIS and Trans are names given to particular arrangements of double bonds or of rings. Okay, so basically, any time that you have no free rotation, okay, you're gonna have the possibility for CIS and trans. So, for example, um, a double bond. If two groups are oriented in the same position, remember that a double bond is is pretty like has a lot of regions of overlap, so it can't twist out of shape. So that means that the old one is stuck there in the same way a ring has the same problem. Where if I, for example, have a ring that looks like this. And then I have a group facing up, and I also have another group facing up. So notice that there's, like, a three D structure. Let's say this is one atom and another atom and see how they're both facing the same way. I can't actually rotate this one to the down position without breaking the ring, because that ring, in order to move one down, you have to snap. So this is CIS and trans of the words that we use for these arrangements that are stuck together. Okay, Onda. Like I said, these items exist because free rotation around pi bonds is impossible. Okay, so basically, the way that we that this works is that when two groups happened to be on the same side of the fence Okay, well, I'm going to talk about that is in a second when they're on the same side, that's gonna be sis. When they're on different sides of the fence, that's gonna be trans. So what kind of mysterious fence am I talking about? Well, let's say we have a double bond. The way that I like to split it up is I like to draw a dotted line right through the middle of the global bond. Okay, so that double bond is my fence. All right. And then what I say is, how are these groups related to each other on that double bond? So, for example, if I wanted to compare A and C, are they on the same side of the fence or different sides? While they're both on the same side, they're both on the top side. So the relationship between and see would be sis. What about the relationship between B and C? What would that relationship be? Well, those are on different sides, so that one would be trans. Okay. Got that so far. How about the relationship between A and B? How would if I were to say, what kind of relationship is that? Okay. And be actually, don't have assistant trans relationship. The reason is because they're on the same carbon. Okay, system. Trans Onley applies to Adams on other carbons, not on the ones that are on your own carbon. So and be would actually get a completely different type of name that we're not going to discuss here, But it wouldn't have to do Assistant trans So Assistant Trans on Lee has to do with the way that one Adam toe another relates to okay, the way that these relate to each other. Okay, so here I've got two different versions of two beauty. Mean, when I say that you shouldn't be shocked, you should know what I'm talking about because that means that's a butane with a double bond in the two position. Easy. Okay, but these air both not both the same molecule. In fact, they're gonna have different physical properties. They're going to behave differently and stuff like that. So what would be the names that we would give to these to show that they're distinctly different? The names that we would give would be what I would draw my fence and I would say, Okay, are these on the same side of the fence or different? Same. So this one would be cysts to beauty, and then this one would be trans to beauty. All right, And these are later on. We're gonna talk about them. There's something called stereo I summers, which means that they actually are connected the same way, but they're shaped differently. But for right now, just know that these are molecules that are locked in their position and they can't move

Now I want to talk about another naming system called E and Z. Okay, so I call this the easy naming system, and it's actually really easy. It's related to System Trans. The only thing is that you use the e and Z naming system when you have multi substituted Al Keane's. Okay, so I know you can barely see that Multi substituted. Even you can't see it and still doesn't make a whole lot of sense. My handwriting is terrible. Okay, so multi substituted al Queens. So let me give you an example. Let's go down to this example here, assigned CIS and trans to the following Calkins. I don't need names. I don't need full names. I just want to know if it's CIS and trans. So let's start off with this first one. Would that one be CIS or Trans? The answer is that this would be trans okay, because if I drew my fence along here, what you would see is that one group is on one side and one group is on the other. Does that make sense? Cool. How about two? What would that be To would be sis? Because both groups are on the same side. Okay. Now, lastly, what about three? What would you say about three? Okay, so three is actually a trick question. There is no assistant, Trans. Why? Because I have three different groups. I have one here. I have one here, so that could be Trans. But then I also have this one over here messing things up. Did I tell you how to figure out System trans when you have three things? No. So, basically, the E and Z naming system is gonna allow us to give unique names to try and Tetra substituted Calkins. What that means is that system trans Onley works if you have two substitutes. But if you have more than two assistant Trans breaks down like in example three example three. There's no way to use system trans there, so I have to use e and Z instead.

when I'm using NZ. All I do is this. I'm gonna choose the highest priority groups on both corners of the double bond. Okay. What does high priority mean? It means highest atomic mess. Okay, so I'm going to try to pick the side of the double bond. I'm gonna try to pick on each side double bond that Adam that has the highest atomic mass. That one's gonna get my priority. And then I'm going to figure out how those two high priority groups are related to each other. If they're related to each other Trans, then we're gonna sign the letter e. If they're related to each other as cysts, then we're gonna sign the letter Z. So basically, Z is just a fancy way of saying cysts with three or more substitutes. E is a fancy way of saying trans with three or more substitutes