Learn about Organic Chemistry 8, in this comprehensive video by bannanaiscool.
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Rob Lederer: One of the most important molecules in organic chemistry is molecule benzene. Now benzene has a formula, C6H6. Now because of this kind of smell and a type of smellingness that's attached to a lot of benzene compound, we call them aromatic. Now aromatics have as a constituent, as a main molecule the benzene rings, C6H6. I mean you put it together, what does it actually look like? Well, C6H6 can only be drawn in this fashion, where you have alternating double bonds inside of a ring of six. So one, two, three, four, five, six carbons in the ring, and everyone of these points would have hydrogen out, because they are carbons, and that makes up for one, two, three, four bonds for every -- carbons. So now, what is that actually be called? Well, it would be a one-three-five trapeze, right, because you need three. So that's three een, so it is a triene, and it's called one-three-five triene. So it's going to be a cyclo one-three-five tri - see, it's a really complicated name. So therefore we just call it benzene. So, it's going to actually have a resonance structure, instead of the one-three-five, it's going to have two-four-six. So therefore we actually have to draw the resonance structure or the structure that exhibits in German, this is what resonance is -- now you don't have to actually draw that all the time. So I just would say, we only want to draw this all these alternative bonds all the time. We don't only want to do that, and we don't want to draw the points on either. All we want to do is draw a circle in the middle and that indicates benzene, that's great, that's easy. So there is your C6H6. Now you can actually put branches on a benzene ring. There is a zillion of them that you can actually do. But once you know how to kind of just put them on a properly naming, it all works out just great, like for instance, if I put a CH3 group here or anywhere there, that's going to be methanol benzene, that's methobenzene, right. How about if I put a bridge there? Well, that's going to be two methos, dimetho on a benzene, dimethobenzene. By the way that's also called o-dimethobenzene; O stands for ortho, that's the one-two position. There are three of them that you have to know for organic chemistry for benzene rings that are called di-substituters, two substitutions on. This is the O position, like, well ortho like as in orthodox just like -- orthodox, just make your teeth closer together, close together, but you want two position, right. I tried. So what else would there be? Well, you can have the one-two position, and then you can put a group in it, I'll put a different here. I'll put this only. So now that's an ethyl, right. So that would be a - and it doesn't matter which one you start at first, the one in the three, the ethyl could be at the one, or the methyl could be at the one, it doesn't matter. So this could be a 1-methyl 2-ethyl benzene, or you could say m-methylethyl benzene. The M stands for meta. Meta is the one-three position, like meta like metaphor, because metaphor, the one and the three equals four, that's very clever. Now then of course, you can have a di-substituted benzene ring where you would have - look at that - chlorine, and a chlorine have the one-four position. The one-four position is designated as para. So this would be called a parachloros or let's say, it would be a p dichlorobenzene, or para dichlorobenzene, that's interesting. There is another one coming up later, that is very interesting, and I'll show that you with the chlorines and the benzene. There are lots of substitutions that you could have on there, and you could do some crazy ones like this. If somebody says name that, you go -- but then just remember, list the halogens alphabetically, that's their complexity order because there is not really any one is more complex than the other, and you would need something like that since one-two-three-four, I would say that you would have a one-four-dichloro - but you're going to have be