Let's talk about naming anhydrides. So an anhydride is a priority group on our chart here. It is the second
highest priority group. It will subjugate any group below it in the table with its subordinate group prefix
and we're not going to use a subordinate group prefix for anhydrides in the presence of carboxylic acids
as we'll see in just a moment, why. We're going to follow our general strategy of circling the parent chain,
writing the name of the subordinate groups that intersect that parent chain, we'll number that chain
and assemble the name and check for stereochemistry as we do that
One quick note -- alkenes and alkynes will be included in suffix form and do not have subordinate group names
when they are included in the parent chain
So we'll have examples of those in other videos discussing these priority functional groups
So let's look at anhydrides specifically here
and when that anhydride is the highest priority group and nothing else is present. So what we're going to do is
name each side as a carboxylic acid and then put the total name together
So 1-2-3. 1-2-3. We've got propanoic on either side
So if these are carboxylic acids, they would be named as propanoic acid, but since they are an anhydride -- and a symmetrical anhydride, at that --
we will call this propanoic anhydride
Now for our second, we have a non symmetrical or unsymmetrical anhydride, and again, 3 carbons. 1,2, and 3 starting with the carbonyl
1,2, and 3. On one side, we still have propanoic
would be acid if it weren't an anhydride, but here we have a 2-chloro
propanoic side
and we put the name together in alphabetical order for an unsymmetrical anhydride
The "C" comes before "P", so we have a 2-chloropropanoic (second word) propanoic (third word) anhydride
So overall here,
we see a 2-chloropropanoic propanoic anhydride
Anytime you have an unsymmetrical anhydride you just name each side as its own carboxylic acid here, and then
put the names together in separate words, alphabetical order followed by a separate word, anhydride, at the end.
When there are multiple anhydrides present it's a little bit complicated, but what we want to do is name it like a dioic acid
and then the individuals on the end. So here we have ethanoic
and on the other end we have an ethanoic end.
And in the middle we have our dioic acid derivative. 1,2, and 3. So that would be a propanedioic acid if it were its carboxylic acid
form. Instead here, for the full name, we would have, in alphabetical order, a diethanoic propanedioic anhydride
And the reason we don't include anhydride group name here in the presence of its only higher priority group
in our course that we're going to see -- is a carboxylic acid -- is because the tendency that we could see the carbonyl form here and the nucleophilic
lone pair potentially attack one of these carbonyls, to form a tetrahedral intermediate, and end up kicking off this other group. So in other words,
anhydrides are reactive with carboxylic acids, and so we won't see that in nomenclature