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Amides, Anhydrides, Esters and Acyl Chlorides : Carboxylic Acid Derivatives - Amides, Anhydrides, Esters and Acyl Chlorides
相關課程
- What I want to do in this video is talk about a bunch of
- molecules or classes of molecules that can be derived
- from carboxylic acid.
- And just to show a specific example I'll show things that
- can be derived from acetic acid.
- And just as a review, acetic acid looks like this.
- The common name, as I just said, is acetic acid, and if
- you want to use the systematic name, you look for the longest
- chain, which is right over there.
- There's two carbons.
- So we use the eth- prefix, so it's ethan-, and since this is
- a carboxylic acid, it is ethanoic acid.
- Now, the derivatives of acetic acid, and we can later
- generalize this to all carboxylic acids.
- We really just have to change what's going on in this carbon
- chain right here.
- It won't have to necessarily just be two carbons.
- It can just keep going.
- It could have benzene rings, whatever, and that would
- change the name.
- But really, I just want to give you the gist and the gist
- of the naming.
- So if we were to replace this hydroxyl group with an amine,
- and in future videos we'll see how that is done, so let me
- just draw the acyl group.
- So the acyl group is just that right over there.
- And we're just going to keep changing what's bonded to the
- acyl group right over here.
- So if this is bonded to an amine, so let me draw-- well,
- this would be the simplest amine right over here, which
- would be NH2.
- This thing right here it's called an amide, and if we
- were to give this its common name, it would be acetamide.
- This particular example would be acetamide.
- And if we wanted the systematic name for it, it
- would be ethanamide.
- You have two carbons right there so it is ethanamide.
- Now the natural question is, all amines won't just be
- primary, you might have other things other than hydrogens
- attached to it, other radical groups, other carbon chains,
- so how do you name those?
- And so if you had a molecule that looked like this, and
- actually, let me just change things up a little bit so that
- we diverge a little bit from the ethane route.
- So let's say you had three carbons bonded or part of the
- acyl group right there.
- And then, we are bonded to a nitrogen, which is bonded to a
- methyl group and then another hydrogen.
- In this case, you start naming with this methyl group right
- here and to show that that methyl group is attached to
- the nitrogen, you call this N-methyl.
- And then you look at the chain that forms the acyl group, the
- carbon chain.
- We have one, two, three carbons so it is propanamide.
- If you had another methyl here you would say N comma
- N-dimethyl.
- If you had a methyl here and a propyl group here, you
- would've called it N-methyl-N-propyl-propanamide.
- So hopefully that gives you a sense of amides.
- Now, and this is something we've seen before so it's a
- little bit of review, if you have something that looks like
- this, I'll have it attached to a methyl
- group right over here.
- We've seen this before.
- This is an ester.
- And if we have an-- let me actually make the part that
- makes it an ester in blue to diferentiate it.
- We keep substituting what is attached to the acyl group.
- Let me label it.
- This right here is called an acyl group.
- That right there is an acyl group.
- So right over here, for the ester, if we were to give it
- its common name, and we've seen this ester
- before, it is acetate.
- And if we wanted to give it its systematic , name you look
- at the longest chain, one, two carbons so it is ethan-- and
- you don't call it ethanoic acid anymore.
- You call it ethanoate, just like that.
- Now, the next one, and we haven't seen this one before,
- and it looks complex, but when you really break it down into
- its constituents, it's not so bad.
- So let's say we have a molecule that looks like this.
- So we have one acyl group bonded to an oxygen, which is
- bonded to another acyl group.
- So it's almost like you have two carboxylic acids that have
- been joined together.
- And you really do have two acyl groups joined by an
- oxygen here.
- This is called an anhydride.
- And they look very complex, but you just have to realize
- they're two carboxylic acids attached to each other and
- usually the same one.
- Most anhydrides you're going to see in organic chemistry
- are formed from the same carboxylic acid, so how ever
- many carbons you have on this end, you're normally going to
- have on this end.
- So the way the name these is you name it just the same way
- that you would have named the carboxylic acid, but instead
- of writing the word acid, you write the word anhydride.
- So this right here would be acetic anhydride.
- It's derived from acetic acid.
- This right here is acetic anhydride.
- Or the systematic name is, we have one, two carbons so it's
- ethanoic anhydride.
- And just to make things clear, if this molecule instead of
- that, if we had something that looked like this, where the
- carbons chains on either end had three carbons.
- One, two, three, one, two, three.
- We would call this propanoic anhydride.
- In the unusual circumstance, and it is unusual, where you
- would see different carbon chains here, you would list
- each of them.
- So if this had two here and three here, it would be
- ethanoic propanoic anhydride.
- But that is very, very unusual.
- Normally, these carbon chains on either end of-- or both
- acyl will groups will contain the same number of carbons.
- Now, the last carboxylic acid derivative that you should
- know about, and we've already seen it, are the acyl halides,
- and, in particular, the acyl chlorides.
- So let me draw it right over here.
- So you have your acyl group right there and then it is
- bonded to a chlorine and this right here is an acyl
- chloride, maybe the most intuitive name.
- This right here is an acyl group and then you have a
- chlorine, so it's an acyl chloride.
- And we've seen this exact acyl chloride.
- It's derived from acetic acid, so this is acetyl chloride.
- But if you wanted to give it its systematic name, and we
- haven't seen it's systematic name before, we have one, two
- carbons so it is ethanoyl.
- This tells us that we are dealing with an acyl group.
- Ethanoyl chloride is how we would name this.
- And if this had three carbons, it would
- be propanoyl chloride.
- So, hopefully, that gives you at least a good introduction
- to the differences in structures of all these groups
- and an introduction to naming them.
- In the next video, we'll talk a little bit about the
- relative stabilities and then it'll give you good intuition
- on which direction a reaction might go.
- Are you more likely to go from amide to an acyl chloride or
- from an acyl chloride to an amide or anything in between?
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