Ethers are one of the few functional groups that are more often named with common names vs. IUPAC names. Regardless, we’ll learn how to use both naming systems.
List both alkyl groups in alphabetical order and follow with the word ether.
Concept: How to name ethers using the common naming system.2m
Now let's talk about naming ethers. It turns out that ethers are very simple molecules. As you guys remember, the functional group is ROR. What that means is that since they're very simplistic molecules, these are actually going to be a few molecules that we name with both common names and IUPAC names.
Now if you guys remember IUPAC names are the ones that were developed after 1919 at the IUPAC convention. That means every name that we have for a molecule before that date is considered a common name. It turns out that because ethers are so simple, a lot of times we're going to use common names more often than the IUPAC names for them. So let's actually go ahead and start off learning the common way first and then I'll teach you guys the IUPAC way as well.
It turns out that the common name, the reason we use it so much is because it's very easy to use. All it is is that you name the two R groups in alphabetical order and you end with the word ether. I'm sure you guys have maybe already started lab and you maybe have worked with any ether in lab. They have diethyl ether, dimethyl ether. That just means that the two R groups are either methyls or ethyls.
In this case, this would be a methyl propyl ether because as you can see, I have an ROR functional group and I'm just naming the two alkyl groups according to their size. So I have a one carbon and a three carbon so that would be methyl propyl ether. See how easy that is.
So most of the time we're going to use the common naming system for very simple ethers.
Give the longest carbon chain the root name, then name the smaller chain as an alkoxy substituent.
Concept: How to name ethers using the IUPAC naming system.3m
But it does turn out that sometimes ethers get more complex. Sometimes they have bigger branches on one side and it might be advantageous to use IUPAC. Let's go ahead and see what this same ether would look like if we used the IUPAC convention.
For IUPAC what we would do is we would use the same rules that we use for naming alkanes, but we would name the OR group as a substituent instead. What I would say is which of my R groups is the biggest one. In this case, I have a one-carbon side and a three-carbon side, so obviously, I'm going to use my three-carbon side to be my root. In this case, my root is going to be propane. I know that I'm dealing with propane.
Now I just have to name the OR group that's attached to it. The way that we name OR groups is as alkoxy groups. Alk- just stands for the number of carbons in the chain. You can imagine that if it was a four-carbon chain it would be butoxy. Four-carbons.
In this case, this one's really easy. I just have a one-carbon chain attached directly to the O. This would be considered methoxy. But now it's not enough just to say that it's methoxy propane because we know that propane actually has two positions. It has one at the end, which would be the first position here, and it also has the middle position.
Now you're wondering what about the last one. What about carbon three? Remember that carbon three is the same as carbon one because I could always just – it's symmetrical. I could always just put it on three and that would just be my starting point. But I have to name the location, so obviously, what I would do is I would give my priority to the substituent. This would be 1-methoxy propane because it's starting at the first carbon.
Pretty easy, right? Overall, ethers are pretty easy to name. Let's go ahead and do a practice example. In this example I want you guys to figure out what the common name would be and the IUPAC name would be, both of them together, for this molecule. I want two individual names for this same ether. Go ahead and try it.
Example: Provide the correct common name of the following ether.2m
Example: Provide the correct IUPAC name of the following ether.2m