Leah here from www.Leah4Sci.com and in this video I will show you how to name alcohols.
An alcohol is a molecule that has an OH as its functional group.
This is typically shown as R-OH where R means the rest of the molecule and OH is your alcohol
functional group.
Since alcohol is a high priority functional group, you will add the letters "ol" as a
suffix to your molecule.
Starting with this example, we highlight the parent chain and number so that the OH gets
the lowest possible number.
In this case we have five carbons giving me a first name of "pent".
We have only single bonds giving me a last name of "ane".
Since the alcohol occurs on carbon 2, we add the prefix "2-ol".
When putting the name together, you can bring the 2 to the front of the name and that means
"ol" will directly follow "ane" and so you drop the E.
This gives me a final name of 2-pentanol where it's A-N, instead of A-N-E, O-L.
When you have a substituent on your alcohol, you still follow the same rules where your
substituent becomes the prefix and the alcohol is your suffix.
You may recognize this molecule as having the common name tert-butyl alcohol but let's
see how to name it using the IUPAC rules.
We will start by identifying and highlighting our longest carbon chain.
In this case, there are three carbons and numbering so that alcohol gets the lowest
number.
We have the option of numbering both from the right and the left, each giving oxygen
a number 2.
So I will start numbering from the left.
Having three carbons in my parent chain gives me a first name of "prop".
Having only single bonds gives me a last name of "ane".
Since the alcohol is on carbon 2, I have a suffix of "2-ol" and since the methyl is also
on carbon 2, I get a prefix of "2-methyl".
Putting the name together, remember that the prefix goes first, then the first name, then
the last name and the suffix.
Remember to drop the E from "ane" for a final name of 2-methyl-2-propanol.
The rules for naming a cyclic alcohol are just like straight chain alcohols.
We start by identifying the parent chain, in this case a total of five carbons for a
first name of "pent".
Given that the molecule is a ring, I add the prefix "cyclo".
Only single bonds gives me a last name of "ane".
Since alcohol is the only group on the molecule, I give it a number 1 and then choose to go
clockwise or counterclockwise for a total of five.
The alcohol would give me a suffix of "1-ol".
However, since it's the only group on the molecule, the number 1 is understood and does
not have to be included.
This gives me a final name of cyclopentanol.
A diol is a compound that has 2 OH groups on the same molecule and we will use this
as an example.
My parent chain has a total of six carbons in a ring.
That gives me a first name of "hex" and a prefix of "cyclo".
Only single bonds gives me a last name of "ane".
Since this is a symmetrical molecule, I can choose to number from either direction as
long as one OH group gets number one and the second one gets number two.
I will write 1, 2 to show which carbons the OH groups show up on and then I will put "di"
in front of the "ol" to show that I have two alcohols.
Putting the name together, I get 1, 2-cyclohexanediol.
Notice that I did not drop my E in this case given that I have the consonant D in between
two vowels.
Let's try an example with the pi bond.
Identifying my parent chain, I see that I have a total of five carbons.
If I number from the right, I give my pi bond the number 2.
If I number from the left, I give the alcohol a 2.
Since the alcohol is higher priority than the pi bond, I number from the right for a
total of five carbons giving me a first name of "pent".
Having a pi bond on carbon 3 gives me a last name of "3-ene".
Having an OH on carbon 2 gives me a suffix of "2-ol".
Putting the name together, I get 3-pentene-2-ol.
Notice again that I did not drop the E and that's because I have the number 2 separating
the two vowels.
Let's try something tricky for the final problem.
In this case I have two rings fused together.
So I have to go back to the rules of naming bicyclic compounds.
I start numbering from the bridge head closest to the OH group since that's my highest priority
giving it a number 1 and then follow my way around the ring that has the OH.
Continuing around the ring that has the bromine and then jumping to the bridge carbon that
has nothing on it.
Having seven carbons in my parent chain gives me a first name of "hept".
Having only single bonds gives me a last name of "ane".
Since I have two fused rings, I have to precede with the word "bicyclo," and then I have to
include how many carbons are unique to each ring in the brackets.
I have two carbons unique to the ring portion with the OH giving me 2.
I have two unique carbons to the portion with Br giving me dot 2 and one carbon on the bridge
giving me dot one.
Bromine is my prefix which gives me "5-bromo" and OH is my suffix giving me "2-ol".
Putting the name together, we start with the prefix, then we have the name and finally
we have the suffix.
Putting the entire name together, I get 5-bromobicyclo [2.2.1] heptane-2-ol.
When you have a name this complicated, it helps to use your puzzle pieces as a checklist
to ensure you didn't miss anything.
I have my prefix "5-bromo".
I have the start to my bicyclic compound.
I have my first name and last name and finally I have my suffix