Amides, anhydrides, esters, and acyl chlorides | Organic chemistry | Khan Academy

Summary

This video script delves into the chemistry of carboxylic acid derivatives, focusing on the transformations of acetic acid. It explains the systematic and common naming conventions for various derivatives, including amides, esters, anhydrides, and acyl halides. The script provides examples and illustrates the process of substituting the hydroxyl group with different functional groups, highlighting the structural and nomenclature changes that occur.

Takeaways

• 🧪 Carboxylic acids can be transformed into various derivatives by altering the functional groups attached to the carbon chain.
• 📚 Acetic acid, with the systematic name 'ethanoic acid', serves as a base example for discussing carboxylic acid derivatives.
• 🔍 The process of naming derivatives involves identifying the longest carbon chain and the type of functional group attached to the acyl group.
• 🍃 Amides are formed when the hydroxyl group of a carboxylic acid is replaced with an amine, and are named based on the carbon chain length and amine substituents.
• 🧬 Esters result from the replacement of the hydroxyl group with an alkoxide group, and are named as 'ate' derivatives of the parent carboxylic acid.
• 🔗 Anhydrides are formed by the linkage of two acyl groups through an oxygen atom, and are named by appending 'anhydride' to the carboxylic acid name.
• ⚔️ Acyl halides, specifically acyl chlorides, are created by substituting the hydroxyl group with a halogen, and are named as 'yl halide' of the acyl group.
• 🔑 The systematic naming of derivatives involves using the prefix based on the carbon chain length, such as 'ethan-' for two carbons, followed by the type of derivative.
• 🌐 When different substituents are present on the nitrogen in amides, the naming reflects the positions and types of these groups, like 'N-methyl' or 'N-propyl'.
• 📉 Anhydrides typically consist of the same type of carboxylic acid linked together, but can occasionally have different carbon chain lengths if from different acids.
• 🚀 The script promises a follow-up discussion on the relative stabilities of these derivatives and their implications on reaction directions in future videos.

Q & A

What is the common name and systematic name for the molecule discussed in the script?

The common name for the molecule is acetic acid, and its systematic name is ethanoic acid.

What happens when you replace the hydroxyl group of a carboxylic acid with an amine?

When the hydroxyl group of a carboxylic acid is replaced with an amine, the resulting compound is called an amide.

What is the systematic name for the amide formed from acetic acid and a simple amine?

The systematic name for the amide formed from acetic acid and a simple amine is ethanamide.

How do you name an amide when there are additional carbon chains or groups attached to the nitrogen?

You start naming with the group attached to the nitrogen, such as 'N-methyl', and then name the acyl group based on the carbon chain length, like 'propanamide'.

What is the common name for the ester formed when an acyl group is bonded to a methyl group?

The common name for the ester formed when an acyl group is bonded to a methyl group is acetate.

What is the systematic name for the ester derived from acetic acid?

The systematic name for the ester derived from acetic acid is ethanoate.

What is an anhydride and how is it formed?

An anhydride is a molecule formed when two acyl groups are joined by an oxygen atom, essentially two carboxylic acids joined together.

What is the name of the anhydride derived from acetic acid?

The anhydride derived from acetic acid is called acetic anhydride, with the systematic name being ethanoic anhydride.

How do you name an anhydride when the carbon chains on either end have different lengths?

In the unusual case where the carbon chains have different lengths, you list each of them, such as 'ethanoic propanoic anhydride'.

What is an acyl halide and what is its most common form?

An acyl halide is a compound where an acyl group is bonded to a halogen atom, with the acyl chloride being the most common form.

What is the systematic name for the acyl chloride derived from acetic acid?

The systematic name for the acyl chloride derived from acetic acid is ethanoyl chloride.

Outlines

00:00

🧪 Derivatives of Carboxylic Acids: An Introduction

This paragraph introduces the concept of carboxylic acid derivatives, focusing on acetic acid as a specific example. It explains the systematic naming of carboxylic acids, using 'ethan-' as a prefix for a two-carbon chain, resulting in 'ethanoic acid'. The paragraph outlines the process of creating derivatives by altering the hydroxyl group, such as replacing it with an amine to form amides. It provides a systematic name for this example, 'ethanamide', and discusses the naming conventions for amides with different amine groups. The paragraph also reviews the formation and naming of esters, highlighting the common and systematic names, and introduces the concept of anhydrides, which are formed by joining two acyl groups through an oxygen atom.

05:00

🔍 Exploring Anhydrides and Acyl Halides

The second paragraph delves into the structure and naming of anhydrides, which are derived from two carboxylic acids joined by an oxygen atom. It uses 'acetic anhydride' as an example, explaining that the naming convention involves replacing 'acid' with 'anhydride'. The paragraph also addresses the possibility of different carbon chain lengths in anhydrides, although it notes this is unusual. Finally, the paragraph introduces acyl halides, specifically acyl chlorides, as derivatives of carboxylic acids where the hydroxyl group is replaced by a halogen. 'Acetyl chloride' is used as an example, with its systematic name 'ethanoyl chloride' also provided. The paragraph concludes by setting the stage for a discussion on the relative stabilities of these derivatives in future videos.

Keywords

💡Carboxylic Acid

Carboxylic acids are organic compounds containing a carboxyl functional group (-COOH). In the script, the focus is on acetic acid, which is the simplest carboxylic acid and serves as the basis for discussing various derivatives. The term is fundamental to the video's theme as it introduces the starting point for the formation of different molecular classes.

💡Acetic Acid

Acetic acid is a specific type of carboxylic acid with the chemical formula CH3COOH. It is the primary example used in the script to illustrate the concept of carboxylic acid derivatives. The script explains its common and systematic names, emphasizing its role in the formation of other molecules.

💡Ethanoic Acid

Ethanoic acid is the systematic name for acetic acid, derived from the longest carbon chain in the molecule, which has two carbons. This term is used in the script to demonstrate the systematic naming convention for carboxylic acids, which is essential for understanding the nomenclature of their derivatives.

💡Derivatives

In the context of the video, derivatives refer to the different classes of molecules that can be chemically derived from carboxylic acids, specifically acetic acid. The script explores various derivatives, such as amides and esters, showcasing the diversity of chemical structures that can be formed from a single starting compound.

💡Amide

An amide is a compound formed by the replacement of the hydroxyl group (-OH) of a carboxylic acid with an amine group (-NH2). The script introduces the concept of amides by showing how they are derived from acetic acid and provides an example with the systematic name 'ethanamide'.

💡Ester

Esters are compounds formed by the reaction of a carboxylic acid with an alcohol, where the hydroxyl group of the acid is replaced by an alkoxy group. In the script, the ester derived from acetic acid is called 'acetate,' and its systematic name is 'ethanoate,' illustrating the formation of esters and their naming.

💡Acyl Group

The acyl group is the functional group in carboxylic acid derivatives, consisting of a carbonyl group (C=O) bonded to an alkyl or aryl group. The script uses the acyl group to explain the structural basis for amides, esters, anhydrides, and acyl halides, emphasizing its importance in organic chemistry.

💡Anhydride

An anhydride is a compound formed by the removal of a water molecule (dehydration) from two molecules of a carboxylic acid, resulting in an oxygen bridge between two acyl groups. The script describes 'acetic anhydride' as an example, showing how anhydrides are named and derived from carboxylic acids.

💡Acyl Halide

Acyl halides are compounds in which the hydroxyl group of a carboxylic acid is replaced by a halogen, such as chlorine or bromine. The script specifically mentions 'acyl chlorides' and uses 'acetyl chloride' as an example to explain the formation and naming of acyl halides.

💡Ethanoyl Chloride

Ethanoyl chloride is the systematic name for the acyl chloride derived from acetic acid. The script explains how to derive the systematic name by using the number of carbons in the acyl group and the suffix 'oyl' for the carbon chain, followed by 'chloride' to indicate the halogen.

💡Nomenclature

Nomenclature in the script refers to the systematic naming of chemical compounds, which is crucial for understanding and communicating about their structures. The video uses various examples from the derivatives of acetic acid to illustrate the rules of chemical nomenclature, such as the use of prefixes and functional groups in naming.

Highlights

The video discusses the derivation of various molecules from carboxylic acids, specifically using acetic acid as an example.

Acetic acid is systematically named as ethanoic acid, with the longest carbon chain determining the prefix.

Derivatives of carboxylic acids involve changes to the carbon chain, which can include benzene rings or other structures.

Amides are formed by replacing the hydroxyl group of a carboxylic acid with an amine, exemplified by acetamide.

The systematic naming of amides involves the prefix of the carbon chain and the suffix 'amide'.

Different amine groups attached to the nitrogen in amides can be named by their position, such as N-methyl.

Esters result from the substitution of the hydroxyl group with an alkoxy group, like in acetate.

Ester systematic naming uses the prefix of the carbon chain and the suffix 'oate'.

Anhydrides are formed by joining two acyl groups through an oxygen atom, resembling linked carboxylic acids.

Anhydrides are named similarly to the original carboxylic acid but with the suffix 'anhydride'.

Acetic anhydride is a common example of an anhydride, derived from acetic acid.

In the case of different carbon chains in anhydrides, each chain is listed in the name.

Acyl halides, particularly acyl chlorides, are formed by the substitution of the hydroxyl group with a halogen.

Acetyl chloride is an example of an acyl chloride, named for the acyl group followed by 'chloride'.

Systematic naming of acyl halides uses the prefix of the carbon chain and the suffix 'yl halide'.

The video promises to discuss the relative stabilities of these derivatives and their implications in future reactions in the next installment.

Transcripts

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?