Hey guys! Let’s learn how to name ketones. Ketones are going to modify the root name of a carbon chain. You’re going to take out the e ending of the carbon courage chain and then you’re replace it with the suffix -one. I know that looks like one. Please do not say one. It’s pronounced -one like ketone.
In this video, we're not going to discuss the prioritization of all functional groups in terms of numbering locations but just suffice it to say that ketones are going to have higher priority than pretty much all the groups you learned in Orgo 1, including alcohols. If you saw an alcohol and a ketone next to each other, and you had to figure out which one gets the higher priority with naming and numbering, you would pick the ketone.
There’s IUPAC name and there’s common names. When you're assigning common names to ketones, then you’re going to name both of the R-groups alphabetically here and you’re going to end with the word ketone.
Let me just show you a really quick example of the difference between common and IUPAC. Let’s say you have a four-carbon chain with a carbonyl in the middle. In IUPAC, the name of this would be, it starts off as a butane, now it's going to be a butanone and you have to name the location because I need to know exactly where that ketone is. It could be anywhere. I’m going to name this as a 2-butanone. That would be IUPAC.
In terms of common naming, it would be a little different. For the common name, you would just name the substituents in alphabetical order and end with the word ketone. Then it would be on ethyl methyl ketone, almost like it’s an ether. Remember that ethers you can do that as well. You can name both of the substituents and end with ether. This would be an ethyl methyl ketone.
This common naming system is actually pretty common with a lot of ketones that you’ll find in the lab because in the lab, we work with a lot of smaller ketones. But once you get to larger and more complex ketones that have bigger branching group, the common naming system just becomes impossible to use because now you’re going to have to name these huge bulky substituents in common names and it just gets terrible. You should use IUPAC. Definitely use IUPAC for more complex ketones. It’s okay to use common names for the easier to name ones, the smaller ketones.
We’re going to do two examples. I know you guys got this. Let’s start off with the first one. Obviously I don't need the common name for this. I just want the IUPAC name, so go for it.
Alright, so what was the longest carbon chain? Well it turns out that was a little bit tricky to answer here because we had two of equal length. We had the blue carbon chain that I believe is six carbons long and we had the yellow carbon chain which is also six carbons long.
Which one did you pick? Does it matter? Hell yeah it matters. Guys, this goes back to our alkane nomenclature rules from organic chemistry one and you just need to know that you're going to go, when you have a tie, you're going to go with the one that gives the most substituents meaning that if you look at yellow, yellow would only give me one branch, one substituent. Blue would give me two branches right, two things coming off. The theory behind this is that the more branches you have the easier they're going to be to name because they're smaller so it's easier to name something small or a lot of small things than it is to name one big terrible thing.
So we have the longest carbon chain, it's going to be this guy right here which means that I have a 2, oh not bute sorry, hexanone. 2-hexanone because I'm going to give my priority to the ketone and now I just need to name my substituents so I have a 3-propyl and I have a 4-methyl. So all in alphabetical order, it's going to be 4-methyl-3-propyl-2-hexanone. Easy. So let's move on to the next example.
Alright guys, so this one wasn't so bad either. We've got a root carbon ring of a cycloheptane and we just have to figure out where the substituents go and stuff like that so obviously my first carbon is going to be the ketone. Ketones have priority over pretty much most groups but especially alkyl halides and alkanes which don't have any priority at all. So now you just have to determine which direction do we number in? Do we number in the red clockwise direction or the blue counter clockwise direction? The answer is red because we're just trying to make the substituents have the lowest numbers possible, none of them have priority, so this turns into a 2-iodo and this is a 3, 4, 5-methyl.
So now obviously our cycloheptane becomes cycloheptanone. So we can go ahead and put this all together and it would be, I comes before M so 2-iodo-5-methyl-1-cycloheptanone. Alright guys, and just you know an extra side note here if you wanted to not include that one and just leave it as no location that would also be valid and the reason is because we only have one modifying functional group notice that you only have one modifier. Since you only have one modifier it's okay to leave it off as nothing there, no location, because you assume that it's at the first. Now you absolutely have to put locations if you have two or more modifiers. So if this became like a cycloheptenone now you need the locations. I just like to add locations just be to be explicit and both of them would be correct so if you put a one, it's correct, if you didn't put a one, it's also fine. It would just be the methyl and the cycloheptanone together with no hyphens and no commas. Awesome guys, so pretty easy stuff. Let's move on to the next topic.