Esters can be tricky to name. Why? Because we won't see the word "ester" at all in the name. So how will we name them?
Well, we can name them using both the Common and IUPAC naming system and by breaking apart the functional group in 2. Let's take a look.
Concept: Ester Nomenclature3m
On this page, we’re going to learn how to name esters. Esters are actually one of the hardest functional groups to name that’s because ester is one of the only functional group that the name of the functional group is not found anywhere in the nomenclature. Meaning that if you have an ester, you're not going to actually see the name ester anywhere. So what is the name? It turns out that an ester is names of two components. Imagine that you’ve got an ester. Remember that the general structure is COOR. What they consider is that everything on this side is an alkyl group. You name this as an alkyl group. Then the way that they name the other side is they think this looks a lot like, this side here, looks a lot like a carboxylic acid but without the H. What do you call it when a carboxylic acid is missing its H? You call it a carboxylate. It’s an alkyl carboxylate. That sucks. We name it as an alkyl carboxylate. You have to determine what that name is going to be. I’ll do a work example here and then I'll let you guys go to do it yourself.
Here. We've got an ester, obviously. We have an alkyl group and a carboxylate. The way we would name is the alkyl group is ethyl, two-carbon chain. The carboxylate could be named in one of two ways. It could be named as the common name which should be the two-carbon chain which should be acetic acid, which should be acetate because acetate is the negative anion or, that’s in the common name. Or it could be named as ethanoate because it’s ethanoic acid, so that would be IUPAC. Both of these would be correct. You’ll hear ethyl acetate. You'll hear ethanoate. Obviously, acetate is way more common. You hear that everywhere. Ethyl acetate would be the name of that structure there. Let's go ahead and move on to this practice problem. Let’s see if you can get it right.
Example: Name the structure2m
So guys, I would have accepted two answers for this question. So, if you did common that's fine, if you did IUPAC that's also fine. So, my alkyl group in this case is cyclopentyl, okay? A cyclopentyl group and then my carboxylate in common would be valerate, right? valerate in IUPAC it would be pentanoate, okay? So, both of these are correct. So, I'm going to put here, cyclopentyl Valerate or cyclopentyl pentanoate, okay? Again guys see how tricky, this is that if you didn't take the time to learn it you might not recognize that this is an ester on an exam because it doesn't have the word esther in it, right? It's like who thought of that, someone really messed up. So, see if you guys can go ahead and draw the one below.
Example: Draw the molecule2m
Alright guys. So, what I would do is I would start off with the general structure of an ester, first of all, how I even know what functional group this is? obviously it's on the ester page. So, you're thinking ester but what if you saw this on an exam and just in the middle of a bunch of stuff? Well, what you could think is that I've got an alkyl group and formate is a carboxylate. So, when you see alkyl and carboxylate together that screams ester, okay? Once you've made that connection draw your general structure of an ester. So, I'm going to draw OR and R, okay? Now, all I need to do is really just plug and chug, I just take the R groups from my name and I replace them, so the isopropyl part, does that part go on R1 or R2? what do you guys think? R2, okay? So, that means that, that's my alkyl group, I'm going to write it like this, okay? So, I have isopropyl formate, what type of carboxylic acid is a formate, formic acid is a one carbon carboxylic acid, meaning that this is actually an H, okay? Because it's just the one carbon comes from the carbonyl, so this is your structure, isopropyl formate. Awesome guys. So, let's move on.
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a. benzyl ethanoate
b. phenyl ethanoate
c. ethyl benzoate
d. proply benzoate
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a. phenyl 2-methylpentanoate
b. 2-methylpentyl benzanoate
c. phenyl 2-methylpentanone
d. benzyl 2-methylpentanoate
e. 2-hexyl benzanoate
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