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Organic Chemistry

Learn the toughest concepts covered in Organic Chemistry with step-by-step video tutorials and practice problems by world-class tutors.

12. Alcohols, Ethers, Epoxides and Thiols

Alcohol Nomenclature

We’ve learned how to name simple alcohols before, but now we are moving to polyols.

 

Note: I am moving away from the term glycol, and using polyols instead, since the term glycol is not specific enough. 

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concept

How to name polyols.

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ah, functional group that we definitely need to know how to name is alcohols and they're really not so hard. So let's just jump straight into it. So ah, word that we use to describe a molecule that has more than 108 or more than one hydroxyl on the carbon chain is a glycol, and glycol is a very un specific word because it just refers to any molecule that has more than one hydroxyl on it. So instead of using the term glycol, a lot of times we're going to use a more specific term. In fact, we're gonna use prefixes to indicate exactly how many Ohh is are on that change. So, as you can imagine, we're just going to use the same prefixes that we use for all AIPAC nomenclature. If you have an alcohol with two hydraulic souls, that's gonna be called a dialogue. Okay, if you haven't alcohol with three hydroxy, as you can imagine, that's gonna be called a trial. And that would keep going to etcetera, etcetera. Okay, Now keep in mind that something that's unique about alcohol groups is that you always give the most priority or the highest priority in terms of the way that you number the chain or the way that you number the ring to the O H group. Okay, so there's actually this phrase that we use in or go one that just says alcohol beats all okay. And that just means it's gonna be all the other functional groups that you're really exposed to in or go One. If you have a double bond, triple bond, alcohol highlight, anything else present, you're going to give your priority in terms of prioritizing, numbering to the alcohol. Okay, so let's just go ahead and jump into these examples. I want us to try to solve it on your own, and then I'll go ahead and jump in and give you guys the answer.

In Summary:

Polyols with two hydroxyls are called diols, and polyols with three hydroxyls are called triols.

  • Always give most priority to the –OH group.
2
example

Provide the correct common and IUPAC name.

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All right, so let's go ahead and start off with the root name. The root for this compound would be cyclo hexane. Right? So let's go ahead and write that down. Great. So I got cyclo heck saying, but obviously have some substitutes coming off this. In fact, these air functional groups, I have to alcohol's so I can imagine that my modifier is gonna be dialing. Okay, so I'm just gonna put here Mod is dialing. So I could put these two words together, and I know that this is going to be a cyclo, hex and dial. Okay, so I just put the modifier at the very end of the route. Now we need locations, right? Because I don't know exactly where these alcohols are. What we would do is we would just give top priority toe one of the alcohol's. It doesn't matter which one you choose, since they're both the same thing. But we do know that if one it had been an alcohol and the other one was, for example, a halogen, I would give my highest priority to the alcohol, Right, Because alcohol beats all. Let's just pick. This is my one. That means that my other alcohol is going to be at the three. So this is going to be a one comma, three cyclo hooks and dial. So are we done? We're so close. But there's one more thing you have to add, and that's gonna be the relationship of the O. H is to each other in terms of where they are in space or their stereo chemistry. So remember that if you have two groups on the same side of the ring or different sides of the ring, they get different names, right? So if they're on different sides of the ring that would be considered trans. This would be The trans stereo is, um, er of 13 cycle hooks and dial. Alright, so not so bad. Let's go ahead and try to name this other example. Go ahead and try to do it on your own, and then we'll give you guys the answer

Note: The molecule should be named trans-1,3-cyclohexanediol. 

 

There are other possible name variations that are also acceptable. Here are just a few:(R,R)-cyclohexane-1,3-diol, (1R, 3R)-1,3-cyclohexanediol

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example

Provide the correct common and IUPAC name.

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All right, So this one is a piece of cake. We know that the root is propane because I have a three carbon chain and I have to Alcohol is in the same position. So this is gonna be my one because alcohol gets the highest priority. This is gonna be a one comma, one propane dial. Okay? And just so you know, that's the full name. Many times these air gonna be more generally referred to as what we call Jem dials. Okay, the reason we call it a gem dial is because I have to. Alcohol's coming off of the same position. And when you have two things coming out for the same position we call the Germinal. So the gem in this case stands for gem inal dial. And that's actually gonna be really important thing. When we get into or go to, we'll talk about gem Dial's all the time. All right? So hopefully that helped. Let's move on to the next topic
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