 Hi, I'm Professor Steven Nesheva and I want to talk to you a little bit about line drawings of conjugated alkenes. So line drawings are kind of a condensed way to represent molecules, especially organic molecules. And as an example I've got here, it's a propane, the name of the molecule. You can see that it has three carbons and each carbon is bonded to four other atoms, or at least has four bonds. In this case the carbon has three hydrogens, this one has two, because it has two carbons that are attached to it and so forth. So the line drawing of this one is just written this way. You can kind of see that the geometry is similar to the way the carbons are laid out. The rule is that at the end of a line, that's supposed to indicate a carbon. Anywhere there's a kink in a line, like there, that's another carbon. And so that's, I can look at this and I can see that there are three carbons. We don't draw any hydrogen that's attached to a carbon in a line drawing because it's understood that there are three hydrogens attached to that carbon two there and three there. So the generic term for a molecule that just has carbon and hydrogen and with all single bonds is called an alkane and and so that's kind of how that works. The, you know, the next, you know, molecule, the next longer molecule like this would just be written this way and that would be butane. You can see that it would have four carbons and so on. I'm going to move on to an alkene and this difference in the vowel here tells you that there's a carbon-carbon double bond and so here is a molecule called propene. You can see it has a double bond. I'm just working through how this translates. I can see that there's an end and a kink and another kink that tells me that there are three carbons here. No, there's no hydrogens drawn here because that's the convention in the line drawing but I can tell that since this carbon is bonded to two other carbons it must have, I'm sorry, it has a double bond to another carbon. It must have two hydrogens attached to it. How many hydrogens are attached to that carbon? Well, this carbon forms one, two, three bonds. So it only has room for one more and finally I have this last carbon. It's only bonded to one carbon. So it must have three hydrogens attached to it. So again, this is an alkene because it has a carbon-carbon double bond and you know another alkene could be written like this, something like that, that would be one, two, three, four carbons and that would be called a variant of a butane. The next last idea I just kind of want to talk about here is whenever you have a situation in which you have multiple carbon-carbon double bonds and when they are in the sequence double bond, single bond, double bond, and so on, that is called a conjugated alkene and in this case I can see that there are three double bonds that are conjugated. Now the rule is in order to be called a conjugated set you have to have precisely this kind of arrangement. If there's an extra single bond in between then it's not conjugated with each other. So for example here, I have two double bonds. This would form a conjugated part of that molecule. This would form another conjugated part of that molecule, but they wouldn't be conjugated. They wouldn't form one entire conjugated set. So, yeah.