Question Video: Naming an Ester from Its Condensed Formula Chemistry

What name, according to IUPAC nomenclature, does the ester CH₃CH₂COOCH₂CH₃ have?

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Video Transcript

What name, according to IUPAC nomenclature, does the ester CH3CH2COOCH2CH3 have? (A) Propyl ethanoate, (B) ethyl ethanoate, (C) ethoxy propanoxy, (D) propyl propanoate, or (E) ethyl propanoate.

Nomenclature is the choosing of names for things, especially within science. Nomen- is Latin for name, and -clature comes from the Latin word meaning calling. IUPAC is the International Union of Pure and Applied Chemistry. IUPAC have determined a number of rules for naming compounds. The IUPAC name for esters has two parts. But before we name an ester, we need to know what it looks like. This is the displayed formula for a general ester, where this R group, which represents the rest of the molecule, can be an alkyl group, an aryl group, or a hydrogen atom. And this R group can be an alkyl group or an aryl group.

This is the displayed formula of an ester, but the question gives us a condensed structural formula. So let’s rewrite this displayed formula as a condensed structural formula. We write it from left to right. So first of all, we have the first R group, then the carbonyl carbon, then the oxygen atom in the CO double bond, then lastly, the other oxygen atom and other R group.

Now that we know what an ester looks like, let’s look at how to name it. First of all, we need to split the ester at its CO single bond and then find its parent molecules, which are carboxylic acid and an alcohol. These are the molecules that can be used to make the ester. To find which carboxylic acid was used to make the ester, we add an OH group or hydroxy group to the carbonyl carbon. And to find which alcohol was used to make the ester, we add a hydrogen atom to the oxygen atom in the other part from the ester molecule.

Now that we have our two parent molecules, we need to name them. Finding the names of the ester’s parent molecules will help us find the name of the ester. To find the first part of the ester’s name, we take the first part of the alcohol’s name and add the suffix -yl. To find the second part of the ester’s name, we take the first part of the carboxylic acid’s name and add the suffix -oate. Now that we know how to name an ester, let’s look at the ester given in the question. To make this easier, first of all, let’s draw the structural formula. As before, we go from left to right. We start off with a CH3 group, then a CH2, then the carbonyl group, the singly bonded oxygen atom, and, finally, the other CH2 and CH3 group.

Our first step involves splitting the ester at its CO single bond. We then need to find the ester’s parent molecules, which are a carboxylic acid and an alcohol. These are the molecules that can be used to make the ester. To find the carboxylic acid used to make the ester, we add an OH group or hydroxy group to the carbonyl carbon. And to find the alcohol used to make the ester, we add a hydrogen atom to the oxygen atom in the other part from the ester molecule. Our next step involves naming this carboxylic acid and alcohol. The carboxylic acid contains three carbon atoms, giving the prefix prop-. They are singly bonded, giving -an-, and of course it contains the carboxylic acid functional group. So we add -oic acid to the end of the name. Therefore, our carboxylic acid is propanoic acid.

The alcohol contains two carbon atoms, giving us the prefix eth-. They are singly bonded, giving us -an-. And of course, it contains the alcohol functional group, giving us the suffix -ol. Therefore, the name of the alcohol is ethanol. Now that we have the names of the parent molecules to the ester, let’s start naming the ester itself. For the first part of the ester’s name, we need to take the first part of the alcohol’s name, which is eth-, and add the suffix -yl. This gives us the name ethyl. To find the second part of the ester’s name, we need to take the first part of the carboxylic acid’s name, which is propan-, and add the suffix -oate. This gives us the name ethyl propanoate.

So the answer to the question “What name, according to IUPAC nomenclature, does the ester CH3CH2COOCH2CH3 have?” is (E) ethyl propanoate.

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