Identifying functional groups
How to identify functional groups present in organic compounds.
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- Hi, just out of curiosity, do carboxylic acids form resonance between the two Oxygens bonded to the carbonyl? If so is that the reason carboxylic acids are considered so different to alcohols?(19 votes)
- Can you tell me how to name the last molecule in the video?(6 votes)
- The last compound in the video is 1-aminopropan-2-one.(4 votes)
- I found out that aspirin's systematic name is 2-acetyloxybenzoic acid. however, in identifying the functional groups in aspirin, Sal didn't mention an acetoxy group. Does aspirin contain an ester group, an acetoxy group, both, or another group which combines these two into one? Thanks in advance!(3 votes)
- The general name for the functional group is an ester group.
The systematic name of the CH₃COO- group is acetyloxy.(8 votes)
- So in all of the molecules, are the single bonds, or alkanes, not considered a functional group? Is it only the alkenes, alkynes, and the rest?(2 votes)
- I think its because we set the alkanes as the reference and most simple type of organic compound.(3 votes)
- When the presenter was showing the functional groups for the atenolol why did he call the NH an amine when it did not have two hyrdogens as it did in the examples he showed below?(2 votes)
- The nitrogen of an amine does not need to be bonded to 2 hydrogens.
- Hi, when we name the simple ones we will use number of carbon and their fuctional group but how could we name the complex ones with more than 2 organic compounds in them?(2 votes)
- Functional groups have different priorities when it comes to naming. They are assigned priorities based broadly on their reactivity. So for example a carboxylic acid will have a higher priority than an alkene or alkyne. The highest priority functional group will be the molecule's overall suffix and will determine the class of the molecule. The lower priority functional groups will be considered substituents and be represented as prefixes in the molecule's name. Functional groups will have different prefixes from their suffixes to distinguish them within the name. For example the amine functional group will use "-amine" as the suffix is it the highest priority group, but use the "amino-" prefix if it is the lower priority group as is a substituent.
Hope that helps.(1 vote)
- At5:12, isn't benzene an arene aromatic compound?(1 vote)
- Yes, you're right. Technically, he should have used the formula Ar-CHO.
But many chemists use the symbol R for any group, whether it is alkyl or aryl(3 votes)
- what wil be the systematic name for glucose that is C6H12O6(1 vote)
- (2R,3S,4R,5R)-2,3,4,5,6-Pentahydroxyhexanal(3 votes)
- What does the benz- in benzaldehyde stand for? What makes it different from acetophenone except for the fact that it's an aldehyde while the latter is a ketone? Why would that mean it's an acetophenone? Thanks in advance to anyone who can understand and answer my question(s). :-)(2 votes)
- Is an isoprene ever a functional unit? Would I be correct to describe geraniol as 2 isoprene units and an alcohol?(2 votes)
- Yes, structurally, the skeleton of geraniol consists of two isoprene units.
But an isoprene unit is not a functional group.
A functional group would be a double bond or an alcohol group.
The functional groups in geraniol are the two C=C double bonds and the alcohol group.(1 vote)
- [Voiceover] Let's practice identifying functional groups in different compounds. So this molecule on the left is found in perfumes, and let's look for some of the functional groups that we've talked about in the previous videos. Well here is a carbon-carbon double bond, and we know that a carbon-carbon double bond is an alkene. So here is an alkene functional group. Here's another alkene, right, here's another carbon-carbon double bond. What is this functional group? We have an OH and then we have the rest of the molecule, so we have ROH. ROH is an alcohol, so there's also an alcohol present in this compound. Next let's look at aspirin. So what functional groups can we find in aspirin? Well, here is an aromatic ring. So this is an arene, so there is an arene functional group present in aspirin. What about this one up here? We have an OH, and the oxygen is directly bonded to a carbonyl, so let's go ahead and write that out. We have an OH where the oxygen is directly bonded to a carbon double bonded to an oxygen, and then we have the rest of the molecule, so hopefully you recognize this as being a carboxylic acid. So let me go ahead and write that out here. So this is a carboxylic acid. All right, our next functional group. We have an oxygen, and that oxygen is directly bonded to a carbonyl. So here's a carbon double bonded to an oxygen, so let's write this out. We have an oxygen directly bonded to a carbonyl, and then for this oxygen, we have the rest of the molecule so that's all of this stuff over here, and then, on the other side of the carbonyl we have another R group. So I'll go ahead and write that in, so that is an ester. RO, C double bond O, R, is an ester. So there's an ester functional group present in the aspirin molecule. Let's look at some of the common mistakes that students make. One of them is, students will say a carboxylic acid is an alcohol. So let me write out here a carboxylic acid, so we can talk about that. So sometimes the students will look at that and say, oh, well I see an OH, and then I see the rest of the molecule, so isn't that an alcohol? But since this oxygen is right next to this carbonyl, this is a carboxylic acid. So this is an example of a carboxylic acid. If we moved the OH further away, from the carbonyl, let's go ahead and draw one out like that. So here is our carbonyl, and now the OH is moved further away, now we do have an alcohol, now we have an OH and then the rest of the molecule. So this would be, we can go ahead and use a different color here. So now we are talking about an alcohol, so this is an alcohol. And what would this one be? We have a carbonyl and then we have an R group on one side, an R group on the other side. That is a ketone, let me draw this out. So when you have a carbonyl and an R group on one side, an R group on the other side, they could be the same R group, they could be a different R group. Sometimes you'll see R prime drawn for that. So this is a ketone. So now we have a ketone and an alcohol, so two functional groups present in the same compound. So hopefully you can see the difference between this compound and this compound. This one is a carboxylic acid, and this one is a ketone and an alcohol. Another common mistake that I've seen a lot is on this functional group right here, on aspirin, students will look at this oxygen here, and say, okay, I have an oxygen, and then I have an R group on one side, and I have an R group on the other side. So an R group on one side of the oxygen, an R group on the other side of the oxygen, isn't that an ether? Well, this is, ROR would represent an ether, however, we have this carbonyl here. So this carbonyl right next to this oxygen is what makes this an ester. How could we turn that into an ether? Let me go ahead and redraw this molecule here. So I'll first put in our ring, so I drew the double bonds a little bit differently from how I drew it up here but it doesn't really matter, and then I'll put in our carboxylic acid up here, and now, when I draw in this oxygen, I'm gonna take out the carbonyl. So now the carbonyl is gone, and now we do have an ether. So this actually is an ether now, we have an oxygen, we have an R group on one side, and we have the rest of the molecule over here on the other side, so now this is an ether. So hopefully you see the difference there. Look for the carbonyl right next to the oxygen, that makes it an ester. All right, so more common mistakes that students make is they mix up these two functional groups, so let's look at the functional groups in these two molecules here. And we start with benzaldehyde, and the name is a dead giveaway as to the functional group, we're talking about an aldehyde here. So first, we have our aromatic ring, our arene, and then we have an aldehyde. We have a carbonyl and we have a hydrogen that's directly bonded to the carbonyl carbon. So we have an R group, and then we have a carbonyl, and then we have a hydrogen directly bonded to our carbonyl carbon, that is an aldehyde. If we took off that hydrogen, and we put a CH3 instead, that would be the compound on the right so now we have a CH3 directly bonded to this carbonyl carbon. So now we have an R group on one side, a carbonyl, and then another R group, so we have R, C double bond O, R, and that is a ketone. And you can tell by the ending of our name here that we have a ketone present in this compound. So again, this difference is subtle, but it's important, and a lot of students mess this up. An aldehyde has a hydrogen directly bonded to this carbonyl carbon, but if there's no hydrogen, we're talking about a ketone here, so R, C double bond O, R, is a ketone. Finally, let's look at one giant compound with lots of different functional groups, and let's see if we can identify all the functional groups present in this molecule. This molecule, it is called atenolol. This is a beta blocker. So this is a heart medication. Let's look for some functional groups we've seen before. Here is that aromatic ring, so we know that an arene is present in atenolol, so let me go ahead and write this in here. Next, we have an oxygen, and there's an R group on one side of the oxygen, and an R group on the other side of the oxygen, so ROR, we know that's an ether. So there's an ether present in this compound. Next, we have an OH, and then the rest of the molecule. So ROH would be an alcohol. So there's an alcohol present. All right, next we have a nitrogen with a lone pair of electrons. There's an R group on one side, there's an R group on the other side. So this is an amine. So we have an amine, and finally, over here on the left, so this is one that is messed up a lot. We do have a nitrogen with a lone pair of electrons on it, so it's tempting to say we have an amine here. But this nitrogen is right next to a carbonyl, so it's not an amine. It's an amide, or amid. So this is an amide, so a lot of people pronounce this "amid", all right, so it's not an amine. So let's talk more about the difference between an amide and an amine. So let me go ahead and draw out another compound here, so we can see we have our NH2, and then we have our carbonyl. So for this one, we have our nitrogen, directly bonded to the carbonyl carbon. And that's what makes this an amide. We can move these electrons into here, and push these electrons off onto the oxygen. So resonance is possible with this compound. So this is an amide, or an "amid" If we move the nitrogen further away from the carbonyl, let's go ahead and do that over here. So we have our carbonyl, and now our nitrogen is further away. Now we don't have anymore resonance right? You can't draw a resonance structure showing the delocalization of the lone pair of electrons on the nitrogen. So now, now we do have an amine, so this over here, this would be an amine. Let me change colors, let me do blue. This is an amine. And then, what would this functional group be? We have a carbonyl and then we have an R group on one side, R group on the other side, that is a ketone. So this is a ketone and an amine. And then over here, we have an amide, or an "amid", so make sure to know the difference between these. I've see a lot of very smart students mess up the difference between these two functional groups.