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Current time:0:00Total duration:5:44

Video transcript

so here's a picture of the cubane molecule which is an alkane that's shaped like a cube and for that reason it's one of my favorite molecules I just think it's really cool looking and you can see that at each of the corners of the cube there is a carbon so they're eight carbons total and then there's also a hydrogen coming off of each of those carbons for a molecular formula of C 8 h 8 at first chemists a lot of chemists didn't think this molecule could be made because of the high amount of angle strain that's present in this molecule but it was made starting in the 1960s and it's being looked at for a lot of potential uses in medicine and explosives these days and because you can nitrate it and make things like octa nitro cuban and hep to nitro cuban which are potential explosives for the future and we're going to look and see if we can name cubane using IU PAC nomenclature in this video so let's let's first think about the rules we learned in the video on bicyclic nomenclature and if you're trying to figure out how many rings are in a system you have to make cuts and figure out how many cuts does it take to get to an open chain alkane so if we start with this yellow version of cubane over here on the left I'm going to start cutting bonds and let's see how many cuts it takes to get to an open chain alkane for example I could start by cutting right here so we'll say that's our first cut and then our second cut we could make a cut right back here like that so we could make that my second cut here on on my on my cubane and then for my third cut I'm going to go for this one right up here so we'll take care of that one so that's three cuts so far and then if I just go ahead and take out this one this bond right here and then this bond right here so that's cuts four and five I now get an open chain alkane so it took five cuts for us to do that so there are five rings in cubane so it's Penta cyclo so that's just not immediately obvious to me anyway as as to why there are five rings in cubane so let's go ahead and write Penta cyclo to start the I you pack name here so Penta cyclo meaning five rings and then we start our brackets just like we did in the video on bicyclic nomenclature and to finish name in cubing we're going to pretend like it is a bicyclic compound and the first thing we do is identify our bridgehead carbons right so the comp the carbons that are common to both of the two rings here so hopefully it's obvious those are two rings and those are the bridgehead carbons that connect those two rings when you number a bicyclic a bicyclic compound you start at one of the bridgehead carbons and then you go the longest path first so I'm going to start at this carbon and I'm gonna go the longest path which would be up here so this would be number two this is B number three carbon number four carbon number five and carbon number six which takes me to the other bridgehead carbon and then you name your your next longest path so I'm just going to continue around and make this carbon seven and then make this one back here carbon eight so those are my eight carbons of cubane and so once again I can continue to pretend like it's a bicyclic molecule and the next thing I would do is I would I would name the number of carbons in my longest path so the number of carbons in my longest path would be this one so that would be one two three four carbons remember you exclude the bridgehead carbons when you're doing this so we're going to start with a four right here like that next you do the number of carbons in your second longest path so we can now we can see my second longest path would be this one right here and there are two carbons in my second longest path so I go ahead and put a two over here like that and then finally it's the number of carbons between the bridgehead carbons which in this example of course there are no carbons between my two bridgehead carbons so I would put a zero here like that but of course cubane is not a a bicyclic compound so we have to keep going we have to we have to figure out how I can continue naming this molecule and the way to do it is to next think about how many carbons are there between carbons two and five so if I draw if I draw a dashed line in here right so I can pretend like I'm connecting those two right there and of course there are no carbons between two and five so I can keep going I can make this a zero and then put a 2 comma 5 saying there are no carbons between carbons 2 & 5 and I can continue on I can do that between the 3 and the 8th right so if I were to connect the 3 and the 8th back here like that there are no carbons between 3 & 8 so I can write 0 and then 3 comma 8 and of course I can do the same thing over here on the right so between 4 and 7 there are no carbons right so between 4 and 7 there are no carbons so I can write I can write 0 4 & 7 like that so let me just clear up that 7 there and we're done with our brackets so the last thing you need to do when you're naming your name up when you're naming a polycyclic alkane like this is to figure out how many total carbons are in the molecule well of course there are eight so this is octane so I can go ahead and write octane down here like that and I have my I u-pack name for cubane it is Penta cyclo four two zero zero two five zero three eight zero four seven octane and there are several other molecules that are similar to two cubing which are also very interesting so molecules like dodecahedron would be one to check out as well if you like the structure of cubing