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Course: Organic chemistry > Unit 7
Lesson 4: Nomenclature and properties of ethersEther nomenclature
Rules for naming ethers. Created by Jay.
Want to join the conversation?
- in the very last molecule, shouldn't the ethoxy group given the highest priority instead of the double bond?(12 votes)
- You must start with the double bond in a cyclohexene ring. Then you must number ALONG the double bond towards the substituents so as to give the substituent the lowest number after the double bond from the ring.(21 votes)
- shouldn't (tert-butyl methyl ether ) be called (methyl tert-butyl ether) because it needs to be in alphabetical order?(4 votes)
- di, tri, and tert do not count. In this case we're looking at Butyl and Methyl. That's why tert-butyl goes first.(18 votes)
- Isn't carbon 4 in the cyclohexene also a chiral center?(6 votes)
- Did the original question mean the ethoxy substituent attached to the cyclohexene in the last example in this video, starting at9:35? I was wondering the same thing, because carbon 4 on the ring (the carbon with the ethoxy substituent) would be bonded to -H, -OCC, -CCC=CC, and -CC=CCC (following the bonds around the ring for the last two). Since the double bond placement is different on each side of carbon 4, then technically I think it would it be a chirality center - please correct me if I'm wrong! But I think it was overlooked in the video since the stereochemistry is not actually indicated on the molecule.(6 votes)
- at1:36why is one of the alkyl group called tert-butyl?
what does the tert mean?(5 votes)- The prefix tert means tertiary.
It means that there are three carbon atoms directly attached to the carbon that is attached to the main chain.
The word butyl tells us that that the group contains four carbon atoms.
So a tert-butyl group is (CH₃)₃C—.
Its IUPAC name is 1,1-dimethylethyl.(4 votes)
- What is IUPAC name for tert-butyl methyl ether?(4 votes)
- The IUPAC name for tert-butyl methyl ether is 2-methoxy-2-methylpropane.(4 votes)
- At10:54, that molecule can be named as "1-ethoxy cyclohex-3-ene?"(3 votes)
- You must start with the double bond in a cyclohexene ring. Then you must number ALONG the double bond towards the substituents so as to give the substituent the lowest number after the double bond from the ring.(5 votes)
- why is tert-butyl-methylether called MTBE in laoratories instead of TBME?(3 votes)
- The name arose in commercial laboratories, and they sometimes apply strange names to a chemical.(3 votes)
- At5:56(2-methoxy propane), could it not also be called methoxy isopropane?(2 votes)
- No. IUPAC naming is 2-methoxypropane whereas common naming is with iso in it but the methoxy is attatched to the second carbon so you need to specify that it is number 2. Isopropane states that it is methylpropane but not that there's an ether on it. So you specify it by adding that it is on carbon number 2 rather than one by saying 2-methoxypropane which is how IUPAC differs from common naming.(5 votes)
- 7:48
He named it as 2-bromo-1-ethoxybutane
Shouldn't it be 1-ethoxy-2-bromobutane?
I mean, shouldn't we consider the branches on two sides of "O" as two different and write down their substituents along with it?
ethoxy is one branch and 2-bromobutane is another branch.
2-bromobutane is the parent chain since it is the longest.
But why did he just mix both the alkoxy and alkane part??(3 votes)- He named it 2-bromo-1-ethoxybutane and not 1-ethoxy-2-bromobutane because of the alphabetical rule B comes before E so bromo group was named before oxy group(2 votes)
- At5:28, I see it as a methyl coming off of another methyl instead of propane. Is that correct?(2 votes)
- bit too late to answer lol but nope...it is a propane as per the longest chain of carbons rule, not a methane with 2 methyl groups attached to it as you see it(1 vote)
Video transcript
If we take a look at
this ether, notice we have an R group on
either side of our oxygen. Like that. And if we wanted to
name ethers, there are a couple
different ways to do. We'll start off
with the common way of naming ethers, which follows
the pattern of first naming one of the alkyl groups
attached to your oxygen and then naming the
other aklyl group. And then, followed
by the word "ether." Like that. So alkyl, alkyl, ether. Let's look at an example
of common nomenclature. And we'll start with
this molecule here. So if I wanted to
name this ether, I would first focus in on
what sort of alkyl groups do we have attached
to our oxygen. We're here in the left. That's a methyl group. And over here on the right,
that's an ethyl group. So we need to think
about the alphabet rule. And we know that
E comes before M, so we're going to write
ethyl before methyl. So it will be called
"ethyl methyl ether." Like that. So let's do another one. All right. Our goal is to name this ether. And we first, of course, take
a look at the alkyl groups that we have attached
to our oxygens. So on the left here,
we recognize this as being a tert-butyl group. And on the right, we
have a methyl group. So in thinking about
using the alphabet rule, B comes before M. So
the tert-butyl group is going to come before the
methyl group in the name. So it should be called
"tert-butyl methyl ether." Like that. So the "tert" part isn't
a part of the alphabet. Right? You're comparing the
"butyl" versus the "methyl." Like that. Now tert-butyl methyl ether
might be the correct name-- although, that's
probably not what you will hear this molecule
called in the laboratory. Usually, you'll hear this called
"methyl tert-butyl ether," or "MTBE." MTBE is a very common,
organic solvent. It works very well for
a number of things. And again, MTBE is
what you will hear. But technically, that's
not the correct name. Let's look at an ether that has
alkyl groups that are the same. So if we have this
as our ether, we have two ethyl
groups for this one. So we're going to call
this "diethyl ether." We're going to use the
prefix of "di" here. Now, diethyl ether, of
course, is the famous one. This is the one
that everyone thinks of when they think about ethers. Let's look at another
way to name ethers, and this is the official
IUPAC way of naming them. Now, the common way
of naming ethers is so common that it's
accepted by IUPAC nomenclature. But there is an
IUPAC way of doing it for more complicated
molecules, and that is to name your ether
as a substituent, which we call an "alkoxy." We're going to name
ethers as a substituent and then have a parent alkane. So we're going to call
these "alkoxy alkanes." Like that. All right. So what you would do is, if
you had just this generic ether here like this-- ROR prime--
you would find the larger alkyl group, and that would
be your parent name. So let's say the R prime group
was my longer carbon chain. That would be my alkane name. Like that. And then, you would name
this portion of the molecule as an "alkoxy substituent"
on your alkane. So let's look at an example
of IUPAC nomenclature. So let's go ahead, and
we'll name that first ether that we did a few minutes ago. So the very first one we did. When we're doing
common nomenclature, we call this "ethyl
methyl ether." So let's go ahead and name it
using IUPAC nomenclature here. So what we would do is
find the larger group, and that's going to
be my parent name. So my larger group would be
this over here on the right. And if we were to number
that, you could say that's the number 1 and number 2. If you wanted to. You don't really have
to for this example. But just to get you thinking
about longest carbon chain, that would be
ethane right there. So go ahead and write "ethane"
as our parent alkane name. And then, what do
we have coming off of the ethane portion
of the molecule here? So what is R substituent? Well, this is the ether portion. We're going to name
it as an "alkoxy." And since we have one
carbon to deal with, we know that our root is "meth." And as an "alkoxy,"
it'd be "methoxy." So the complete IUPAC
name for this molecule would be "methoxyethane." Like that. And we don't have to
worry about numbers since we have only two carbons
on our parent chain here. So "methoxyethane" would be the
IUPAC name for this molecule. The common name would
be "ethyl methyl ether." Both are acceptable names. Let's do another one where we
have a very similar-looking molecule, except,
in this case, we're going to add on
another carbon there. So if I'm thinking about
my parents alkane over here on the right, there
would be three carbons for my parent alkanes. So if I wanted to number that,
it'd be one, two, and three. A 3-carbon alkene is,
of course, propane. So I go ahead and write
"propane" right here. And I look at my ether
substituent, once again. And I look, and I see
how many carbons I have. And there's one on
this substituent. So once again, it
would be methoxy. So I'll go ahead and
write "methoxy" in hear. So "methoxy propane." This time I need to
put a number on there. And that group is coming
off of carbon, too. So the complete IUPAC name
would be "2-methoxy propane," Like that. Let's do a much
more complicated one that has a little bit of
stereochemistry in it. So if this was the
molecule that I was trying to name-- and let's
go ahead and put a bromine here like that. All right. So for this one,
once again, I have to think about the larger
group as my parents name. So if I look at those
two alkyl groups, the alkyl group
on the left looks like the longest one to me. And I want to number
to give my substituents the lowest number possible. So if I look over
here on the left, I can see that there are
four carbons in my larger substituent. So four carbons is going
to be my parent name here. So I'm going to
call this "butane." Let's go ahead and start naming
it with "butane" right here. So this would be
"butane" so far. Now, when I number
that butane, I want to give the lowest number
as possible to my substituents. So I could start
from the left, or I could start from the right. And starting from the
right makes more sense because I have a substituent
coming off of carbon one. I have a substituent
coming off of carbon two. And then, three and four. Like that. If I'm thinking about
those two substituents, let's think about how
I would name them. Over here on the right,
for my alkoxy substituent, this time, there are two
carbons in my alkoxy substituent right here. So two carbons would be s,
so that would be "ethoxy." And ethoxy is coming
off of carbon one. So I can go ahead and
write that in here. So "1-ethoxy butane"
is what I have so far. And I also have a bromine
coming off of carbon two. So it'd be "2-bromo." So I can go ahead and put
in "2-bromo-1-ethoxy." And that follows the alphabet. Right? Because B comes before E. So
"2-bromo-1-ethoxy butane." And then, we have to worry
about the absolute configuration at this carbon right here. So carbon two is a
chirality center. So we need to think about
how to assign priority to those 4 groups. So if I think about the
atoms directly attached to my chirality
center-- first, let's go ahead and identify
my chirality center. That would be this
one right here. Four different
groups attached to it because there's also a hydrogen
going away from me in space. And I think about
atomic numbers. Right? So I have carbon versus carbon
versus bromine right here. So bromine, of course, has
the highest atomic number. It gets highest priority. Like that. Now, my hydrogen, of course, is
going to get lowest priority. So that's priority number 4. And now, I have 2
groups to worry about. I have two carbons
to worry about. Let's go ahead and mark
those carbons again. So which one of these carbons
is going to get higher priority? Well, it's all about
what they're attached to. Right? So the carbon on
the left is attached to another carbon
and two hydrogens. The carbon on the
right is attached to an oxygen and two hydrogens. So in terms atomic
number, carbon versus oxygen, the
oxygen will win. And this substituent
on the right would get the highest priority. So this would get
a two over here. All the stuff on the
right would get a two. And over here on the left,
this would be a three. So we have one, two, three
going around this way-- going around counterclockwise,
which is the s absolute configuration. So this is "(s)-2-bromo-1-ethoxy
butane" for the final name. Let's do one more example
of naming an ether here. So let's go ahead and look
at one that has a ring. And we'll put a double
bonds in our ring. Like that. And then, we'll have our
ether over here on the right. OK. So if I wanted to
name this molecule, I would think about
my two alkyl groups and think about which
one is the larger one. And of course, all
this stuff on the left is going to be my parent name. And then, this is going to
be my alkoxy substituent. Like that. So on the left, I know
what that molecule is. I know that's called
"cyclohexene" from an earlier video. Right? So this is "cyclohexene"
as my parent name. I now need to number my ring
to give my alkoxy substituent the lowest number possible. All right. So if I wanted to number my ring
to give my alkoxy substituent the lowest number possible,
I should start here and make that one,
two, three and four. Like that. So we think about-- what
is that alkoxy substituent? It is an ethoxy
substituent because I have two carbons right there. So I have an ethoxy
off of carbon four. So this would be "4-ethoxy." And if you wanted to, you
could put the 1 in here-- "1-cyclohexene." You could leave it
out if you wanted to. So it doesn't really matter. But "4-ethoxy-1-cyclohexane"
gives you all the information that you need if you wanted
to draw this molecule. So that does it for
nomenclature of ethers.