- In this video we will look at the classification
- and nomenclature of alcohols.
- So here we have generic alcohol up the top and have an alcule group on the left.
- and have an OH on the right which is called a hydroxyl group.
- Lets look at the classification of our alcohol so
- If I have a carbon bonded to an OH and that carbon
- is bonded to one other carbon in this alcule group here
- that said to be primary alcohol.
- This carbon over here is bonded to two carbons in those two alcule groups so
- it is therefore secondary alcohol.and
- then this carbon over here on the right is bonded to three other carbons
- so it is said to be tertiary alcohol.
- Lets take a look at the nomenclature of alcohols.lets start with a simple molecules here.
- So if i had a molecule look like that i wanted to name it using iupac nomenclature
- I want to number my carbon chain to give that a away a lowest number possible
- so therefore this carbon we get number 1
- this carbon we get number 2 and for this carbon number 3.
- now that weren't there we would have 3 carbon alkane which we call propane.
- but since we have our OH there this is actually an alcohol
- and alcohol is gonna have the OL endin so this is called propanol.
- so go ahead and write propanol here.
- so OH group is coming off of carbon 1 so we are gonna say this is 1 propanol like that .
- how we classify this alcohol.
- well the carbon right here is bonded to the OH that carbon is bonded to one other carbon
- so this would be a primary alcohol.
- so one propanol is a primary alcohol in terms of its classification.
- lets look at similar looking molecule
- still 3 carbon but this time we put the OH on the carbon in the middle there.
- so once again we are going to number it this is
- carbon 1,this carbon 2,and this is carbon 3
- 3 carbon alcohol those also called propanol.
- The difference is the hydroxy group is on different carbon.
- right its now on carbon 2.so we are gonna go and write 2 propanol here .which is the iupack name
- which is also called isopropanol,rubbing alcohol all the same stuff.
- but 2 propanol would be iupack nomenclature.
- how would you classify 2 propanol
- so once again we find the carbon attached to OH this one how many carbons
- attached to .attached to 1 and 2 other carbon.so therefore this is a secondary
- alcohol.so we have an example of primary alcohol and secondary alcohol here.
- lets do a little more complicated nomenclature question.
- so lets go ahead and draw out larger molecule with more substituents.so
- lets put an OH here and lets do something like that and lets go ahead and do that as well.
- so give the full iupack name for this molecule.
- so you want to find the largest carbon chain that includes the OH.
- and you want to give the OH the lowest number possible.so that gonna mean you are gonna start here
- and make this carbon number 1 .so thats carbon number 1
- this must be carbon number 2,3,4.5,6 and 7.
- So we have a 7 carbon alcohol so 7 carbon alcohol be heptanol so we can start naming this make sure to give us plenty of space here so heptanol
- and we know that the OH is coming off of carbon 2 so we can go ahead and write 2-heptanol
- like that.lets look at the other substituentes that we have.
- well what do we have right here coming off of our ring thats a 3 carbon alcule group
- so that would be propyl so we have 3 propyl.so go ahead and write 3-propyl here.
- like that and what else do we have carbon 5
- we have 2 substituents alright so we have chloro group right here
- ans we have methalic group right here.
- remember our alphabet so c comes before m
- so we can go ahead and put our methyl right here coming off of carbon 5
- so we write 5methyl like that and also coming of 5-chloro that should do it
- everything follows to alphabet rules.
- so we have 5-chloro 5 methyl 3 propyl 2 heptanol for this molecule.
- what about a problem that includes stereochemistery.
- so lets say they give us one where we have to worry about stereochemistery.
- so we go ahead and draw another chain out here.
- so lets make an OH group going away from us.
- and then lets go ahead and make this one coming out at us like that.
- so giving iupack name for this molecule we have to include stereochemistery.
- once again find longer carbon chain that includes OH group.and we want to give
- OH lowest number possible .so it takes precedence over things like alcule groups and
- halogens and double bonds. so we are gonna start from left
- so 1,2,3,4,5,6,7,8,9 like that so we have a 9 carbon
- alcohol so that will be nonanol and the alcohol is coming off of carbon 3
- and OH is coming off of carbon 3 so we have 3 nonanol .
- and lets see other substituents at carbon 6 so at carbon 6 we have a 2
- carbon substituent so that would be an ethylic group so lets go ahead and put in our 6
- ethyl .so for we have 6-ethyl-3 nonanol and we have to worry about stereochemistery.
- put in wedges and dashes on the problem you need to think about
- stereochemistery.and you put those absolute configurations at the beginning
- of the iupack name.so lets figure out the stereochemistery of carbon 3
- so this is our chirality center right here
- this carbon and again you go to the atoms that are directly connected to chirality center
- so thats carbon carbon oxygen and then we also have right coming off our chirality center
- we have hydrogen which is coming out at us like that so that would be the lowest priority
- we get number 4 over here.so oxygen has the highest atomic number
- so thats gonna get number 1 so we have longer chain over here for this carbon
- thats gonna get number 2 then number 3 then the hydrogen will be number 4
- there is little trick that I covered in eariler videos.
- right so it looks if you ignore the hydrogen it looks like you are going around
- counter clock wise so it looks like its s but you have this lowest priority group is coming out
- at you so remember the trick was it would look like its s with those 3.just reverse it
- so it must be R .and must have an absolute configuration of R at carbon 3.so
- go ahead and put in here a 3R.then we will have to worry about absolute configuration at carbon 6
- so carbon 6 here so this is another chirality center.right 4 different substituents attached to it
- there is also a hydrogen attached to this carbon going away from us like that
- and lets think about a highest priority while this chain over here in the left
- this chain is gonna get highest priority
- thats most carbon is definitely gonna get highest prority
- there is more carbon over here in right so again you assign priority its gonna get highest 1
- and then this is gonna get 3rd.
- so this time we have going around 1,2,3.going around counter clock wise
- lowest priority group which is this hydrogen back here is going away from you
- so this actually is going to be S.its counter clock wise so its S.
- so 3R,6S and i want you kind of fast so go back and watch eariler videos
- on absolute configuration if that was little fast for you.
- so lets look at cyclic alcohol so ring systems.
- so lets take a look at alcohol with 6 carbons in a ring and
- OH coming off like that.so 6 carbons without the OH we call that cyclohexane.
- and since this is an alcohol we would just change that to cyclohexanol
- so thats very simple nomenclature cyclohexanol.you dont really need a number
- but if you could right one there its implied if we dont put it in.so thats cyclohexanol.
- what about something that has ring system with 2 hydroxyl groups.
- so lets go ahead and put in some stereochemistery 2.lets say we have an OH coming out at us
- and lets say we have OH going away from us like that alright so when you have a situation
- like this when you have 2 alcohols in the same molecule prefix would be diol.
- and the nomenclature is based off the cyclohexane molecule so you will write
- cyclohexane and then write off cyclohexane where you put the diol .diol meaning two alcohols.
- we have to specify where these two alcohols are on the ring.
- so we need to go ahead and number our ring lets say this is carbon 1 carbon 2 carbon 3 and then carbon 4
- so we have alcohols at the 1 and 4position so go ahead and write 1 and 4 here
- and those 2 alcohols are trans to each other.alright one is coming out at you and one is
- going away from you so you could go ahead and write trans-1,4-cyclohexanediol
- and thats a good iupack name.so there are other types of alcohol.
- we could have instead of cyclohexane ring we can have alcohol based on benzene ring.
- so put in our pi bonds and OH here this is special type of alcohol called phenol
- molecule called phenol and also you will see this hydroxybenzene portion of the molecule
- and lots of natural products.
- this is actually very imporant molecule to recognize the phenols.
- alright so lets go ahead and put something on that ring and we have our phenol is base here
- so lets go ahead and put a bromene (Br) right here so how would we name that molecule.
- the base part of the molecule is phenol molecule so go ahead put phenol like that
- go ahead and number it alright so OH this must be carbon 1
- and want to give substituents lowest number possible so we are gonna give this
- carbon number 2 bromene(Br) coming out from carbon number 2 so its very simple
- we have to write 2-bromophenol like that.
- so thats nomenclature for alcohol and special type of alcohol called phenol
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