Give IUPAC names for the five isomers with the formula C₆H₁₄.

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Welcome back everybody. Our next problem says, provide the Iupac names for all three isomers of C five H 12. We have our choices of a pentane two methyl butane or 22 dimethyl propane bane, one methyl butane, 11 dimethyl propane, C pentane three ethyl propane, 23 dimethyl propane or D pine, two ethyl propane, 22 dimethyl propane. So let's think about what possible structures we have, we have a multiple choice question here. So we have a few hints that eliminate things. For instance, we can see that there are no rings or double bonds in this structure. We would see in the names. Uh If we didn't have multiple choice, we could use the simple calculation, we only have a hydrocarbon here. So we know that that uh simple alkanes have a formula of C subscript NH subscript N plus two. So if they're completely saturated and indeed, we have C five H 12, so therefore, we have no rings or double bonds. But again, we would have that clue from our multiple choice questions in this case. So let's start with the longest chain possible, which would be a chain of five carbons So we just draw that 12345, sorry there tablet turning my zigzag into a straight line. So we have a simple five carbon chain, there's obviously no branches and this would be pentane, which again, we see that's our first choice in all four answer choices. So that's pretty obvious. Now, let's go down by one and make a four carbon chain. So we have a little shorter here. One important thing to note is that this is a symmetrical molecule. So adding something on to either side will result in an identical molecule. So let's keep that in mind. When we look at this, we only have one carbon left over. So we only have a possibility of a methyl branch. If we add our methyl onto either end, we're just extending the chain and making it pentane again. So we need to add it to one of the internal carbons. But again, since it's symmetrical, adding it to carbon two will get the same molecules, adding it to carbon three. So we'll just pop it on here to carbon two. And again, there's only one possible isomer because of the symmetrical nature of this molecule. So we've got one branch on carbon two. So this is two methyl and we've got four carbons. So it's butane. So with that, we can just double check our answer. Choices. Choice A has two methyl butane. So that is correct. But choice B has one methyl butane which doesn't make sense. That would just be pentane. So cross that one out choice C doesn't have any butane option. So that wouldn't be correct. Choice. D has no butane option either. So also incorrect. So we don't even need to go further. If we're on a test, we've already eliminated all but choice. A but in the interest of being through, let's keep going here. We can then make a three carbon chain. So let's do that. 123, we now have two carbons left over. So we might think perhaps we could add an ethel chain. However, we can't add it to either end. And what happens if we add it to carbon two? Well, we've now made a new chain which has four carbons. So we've just duplicated the molecule we made previously to methyl butane. So that isn't going to be a possibility, but we still have two carbons left over. So we could put them both on carbon two. So let's add two methyl groups to carbon two. And that's the only other is only isomer we can make with a three carbon chain. So that will be 22 dye methyl and the three carbons makes it propane. And we see that choice A indeed has 22 dimethyl propane. So the possible isomers for C five H 12 is choice a pentane two methyl butane and 22 dimethyl propane. See you in the next video.

Give IUPAC names for the five isomers with the formula C₆H₁₄.

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Key Concepts

IUPAC Nomenclature

Isomerism

Alkanes