Advanced 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. 

Concept: How to name polyols.

2m
Video Transcript

A 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.
A word that we use to describe a molecule that has more than one OH or more than one hydroxyl on the carbon chain is a glycol. Glycol is a very unspecific word because it just refers to any molecule that has more than one hydroxyl on it. Instead of using the term glycol, a lot of times we're going to use a more specific term. In fact, we're going to use prefixes to indicate exactly how many OHs are on that chain.
As you can image, we're just going to use the same prefixes that we use for all IUPAC nomenclature. If you have an alcohol with two hydroxyls, that's going to be called a diol. If you have an alcohol with three hydroxyls, you can imagine that's going to be called a triol. That would keep going to tetra, etcetera.
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 OH group. There's actually this phrase that we use in orgo one that just says alcohol beats all. That just means it's going to beat all the other functional groups that you're really exposed to in orgo one. If you have a double bond, triple bond, alkyl halide, anything else present, you're going to give your priority, in terms of prioritizing numbering, to the alcohol.
Let's just go ahead and jump into these examples. I want you guys to try and solve it on your own. Then I'll go ahead and jump in and give you guys the answer. 

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

  • Always give most priority to the –OH group.

Example: Provide the correct common and IUPAC name of the following alcohol.

2m

Example: Provide the correct common and IUPAC name of the following alcohol.

1m