Benzene is by far the most common aromatic molecule that we're going to be using this semester. So we're going to have to get really good at the naming of it. And it turns out that since this is a really old molecule, it's going to have some distinct and weird namings that most molecules wouldn't have. Let's just jump right into it. Benzene was one of the first organic molecules to be identified way back in the early 1800s. What we find is that when we're naming these guys common names predominate, meaning that there's IUPAC and there's common and a lot of common names are based on just weird Greek roots, Latin roots, people's girlfriends naming them after their wives and stuff, it's weird. Most of these names are going to make sense thankfully but there are going to be some weird names that you don't have a really great way to understand where those names come from. First of all, we have to know what the benzene derivatives are. Now just so you guys know, your professor may not think that all of these derivatives are important, so you're just going to have to calibrate this knowledge to whatever you learn in class. I'll go ahead and tell you all the names and then I'll tell you which ones are the most important for you to know. Definitely, an alcohol attached to benzene gets the name phenol. Huge. Very important. A methyl attached to a benzene gets the name toluene. An amino group attached to a benzene ring gets the name aniline. A carboxylic acid attached to benzene ring gets the name benzoic acid. This is actually called a methoxy group. Back when we talked about ethers, we learned that ethers can be named with an alkoxy substituent. This would be like an ether, right? R-O-R, methoxy. If you see methoxy, that's called anisole. Like I said, some of these are getting weird. If you see 2 methyl groups, that's not toluene anymore. It would be wrong to call this methyl toluene. Instead, we would call this xylene. See, I told you they're weird. What else? Well, if you have an aldehyde on your benzene, that's going to be called benzaldehyde. That one makes sense. It's kind of like carboxylic acid is benzoic acid. A benzene aldehyde is benzaldehyde. That one was pretty easy. Now, what if you have the most basic ketone, a methyl ketone? We just talked about benzaldehyde being the most simple aldehyde or not the most simple but an aldehyde. Methyl ketone on a benzene ring is actually a weird name. It's acetophenone. Acetophenone. Then finally, if you have 2 alcohols that are specifically in a 1,2 position next to each other, we're going to talk more about what those positions actually, what we call the benzene. But if you have those alcohols right next to each other, that's called a catechol. Now that we've gone through all these crazy names, I'll go ahead and say that they're all pretty important except for maybe the ones that I wouldn't necessarily memorize unless your professor really mentions them in class is anisole. I'm just going to take this one kind of off the list. Don't worry about it too much. Also catechol, I would probably take that off the list. Catechols become really important later in your medical studies when we talk about catecholamines which are neurotransmitters and all you know, their molecules that work in your body. But for right now, just know that this is called a catechol. It's not something I'd need you to memorize at this moment. All these other ones, you're going to see at some point this semester for sure. I would definitely memorize them. Now let's talk about locations. It turns out that the way that you number your substituents actually depends on the number of substituents you have. Mono substituted benzene, no location necessary. If you have a methyl benzene, you should just call it toluene. You should not call that 1 toluene. You don't need to do that. Or let's say that you have a chlorine on the benzene. You should not call that 1 chlorobenzene. You should just name it chlorobenzene. I'm just going to write an example here of Cl and that would be chlorobenzene. Okay? Now guys, I wasn't planning on discussing this right here but this is a better time than any to say, why the heck did I just put a circle inside of that molecule? I have not done that yet this semester but just remember that benzene rings don't always have to be written with 3 double bonds. You could just write a circle and that means that those double bonds are in resonance with each other which we learned is actually the definition. Part of the definition of aromaticity had to do with fully conjugated. If you get an aromatic molecule in the future, you can just write a circle in it if you want to be lazy like me. Notice there's no location there. What if you have disubstituted benzene like I just noticed, I just mentioned 1,2 hydroxyl groups. In that case, we don't use numbers. If you only have 2, we're going to use letter locations. 1,2 instead of being called 1,2, we actually call that ortho. Instead of 1,3, we're going to use the word meta. And instead of 1,4, we're going to use the word para. These even get shorter acronyms. Instead of ortho, we would say O. META would be M. Para would be P. Now these words, they don't all make tons of sense but para definitely means across from, so that helps. META means middle. It's something in the middle. Ortho doesn't technically mean next to. It didn't mean that before. But these days, we'll say that's what the definition is. Next to. Ortho would be next to each other. Para would be across from each other and meta would be in the middle. Those would be the numbers that would correlate to them. This is the way that you name a disubstituted benzene. But what happens guys if your benzene has 3 substituen
18. Aromaticity
Naming Benzene Rings
18. Aromaticity
Naming Benzene Rings - Online Tutor, Practice Problems & Exam Prep
1
concept
Benzene Nomenclature
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Video transcript
2
Problem
ProblemName the following benzene derivative
A
m-toluene
B
o-xylene
C
m-xylene
D
p-xylene
3
Problem
ProblemName the following benzene derivative
A
p-iodoaniline
B
m-iodoaniline
C
p-aminoidobenzene
D
o-aminoiodobenzene
4
Problem
ProblemName the following benzene derivative
A
o-cyclohexylethylacetophenone
B
1-cyclohexyl-2-ethyl-4-acetophenone
C
1-cyclohexyl-6-ethyl-4-acetophenone
D
4-cyclohexyl-3-ethyl-1-acetophenone
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PRACTICE PROBLEMS AND ACTIVITIES (39)
- Name the following compounds: (a) (b) (c)
- Draw the structure of each compound. (a) o-nitroanisole (b) 2,4-dimethoxyphenol (c) p-aminobenzoic acid
- Name the following compounds: (d) (e) (f)
- Name the following compounds: (a) (b) (c)
- Draw and name all the chlorinated benzenes having from one to six chlorine atoms.
- Name the following: d.
- Name the following: c.
- Draw the structure for each of the following: i. m-chlorobenzoic acid
- Draw the structure for each of the following: h. 2,4-dichloromethylbenzene
- Draw the structure for each of the following: g. o-nitroanisole
- Draw the structure for each of the following: f. m-chlorostyrene
- Draw the structure for each of the following: e. 4-bromo-1-chloro-2-methylbenzene
- Draw the structure for each of the following: b. p-nitrobenzenesulfonic acid
- Draw the structure for each of the following: a. m-ethylphenol
- Draw a structure for each of the following: d. m-chlorobenzonitrile
- Draw a structure for each of the following: c. o-nitroaniline
- Correct the following incorrect names: a.
- Correct the following incorrect names: b.
- Classify each compound as an alkyl halide, a vinyl halide, or an aryl halide.d. bromocyclohexanee. 1-bromocycl...
- Classify each compound as an alkyl halide, a vinyl halide, or an aryl halide. a. CH3CHCFCH3 b. (CH3)3CBr c. C...
- Identify the following halogen-containing compounds as a haloalkane, haloalkene, or haloarene. (c)
- Identify the following halogen-containing compounds as a haloalkane, haloalkene, or haloarene. (d)
- Draw a condensed structure and a skeletal structure for each of the following: h. 5,5-dibromo-2-methyloctane
- Give the systematic (IUPAC) names of the following alkenes. f. g.
- For each compound, (1) classify the nitrogen-containing functional groups. (2) provide an acceptable name. (...
- Give a systematic name and a common name (if it has one) for each of the following amines and indicate whether...
- Give an acceptable name for each amine. c.
- Name the following: a. b.
- Draw the structure of each compound.(i) tropylium chloride(j) sodium cyclopentadienide
- Draw the structure of each compound.(m) p-toluenesulfonic acid(n) o-xylene
- Correct the following incorrect names:e. <IMAGE>f. <IMAGE>
- Correct the following incorrect names:c. <IMAGE>d. <IMAGE>
- Draw a structure for each of the following:c. <IMAGE>
- Draw the structure for each of the following:c. 3-benzylpentane d. bromomethylbenzene
- Draw the structure for each of the following:a. 2-phenylhexane b. benzyl alcohol
- Draw the structure for each of the following:d. benzaldehydee. anisolef. styrene
- Draw the structure for each of the following:g. tolueneh. tert-butylbenzenei. benzyl chloride
- Name the following:e. <IMAGE>f. <IMAGE>
- Name the following:g. <IMAGE>h. <IMAGE>i. <IMAGE>