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Ethers and Epoxides Ethers are named by both common and systematic nomenclature of the IUPAC rules. The common names are used for ethers with simple alkyl. ethers are used in many organic reactions where alcohols would be impossible to The naming of epoxides can either be from the starting alkene used to. Simple ethers are given common names in which the alkyl groups bonded to the oxygen are named in alphabetical order followed by the word "ether". TOKYO SAMURAI FOREX

So I'm going to go ahead and put in the OH here like that, put my lone pairs of electrons. And then I have my bromine over here, and I'll go ahead and put in my lone pairs of electrons on bromine as well. And for right now, we can say anything could be attached to this, and we'll go into stereochemistry in the next video.

So what we need to do is add a base. So something like sodium hydroxide will work. So we're going to add in sodium hydroxide, Na plus OH minus. OK, so the hydroxide anion is going to function as a base. All right, so a lone pair of electrons on the oxygen are going to take this proton on our alcohol. And these electrons in here are going to kick off onto our oxygen.

So let's go ahead and draw the result of that acid base reaction. All right, so what do we make from that? Well, now we have our oxygen with three lone pairs of electrons around it like that, which gives the oxygen a negative 1 formal charge. And we still have our bromine here, like that.

And then we still have these other groups attached to our carbon. So in the next step, we need to think about, again, the polarization in the bond between carbon and our halogen, right? Our halogen is more electronegative, so the halogen is going to take a little bit of this electron density in the bond between carbon and bromine and therefore give the bromine a partial negative charge.

Right, this carbon's going to lose a little bit of electron density. So this carbon is actually partially positive. And so the alkoxide that we formed when the alcohol was deprotonated has a negative charge.

It's going to function as a nucleophile. The partially positive carbon wants electrons. It's going to function as an electrophile. And we're going to get a nucleophilic attack by our alkoxide anion on our partially positive carbon. So this is actually an intramolecular Williamson ether synthesis. So if you think about it, right, if these electrons in here are going to attack this carbon, that would kick these electrons off onto your bromine like that. And it's an intramolecular Williamson either synthesis, where your alkoxide is the nucleophile in an SN2-type mechanism.

So if we go ahead and draw the product, right now, this oxygen was bonded to the carbon on the right. Now, it's also a bonded to the carbon on the left, and the bromine left. That was our leaving group. And so we can see that we're going to end up forming an epoxide with this mechanism. So let's go ahead and do a quick problem here. We're reforming an epoxide from an alkene. And we'll start with cyclohexane.

So here is our cyclohexane molecule. And we'll make an epoxide two ways, right? So in the first way, we'll add a peroxy acid, and there are several that you can use. One of the most common ones would be peroxyacetic acid. So peroxyacetic acid looks very similar to acetic acid, except you have an extra oxygen in there, like that. So it's epoxidation of an alkene.

And when we draw our product, right, so let's go ahead and draw our product to form an epoxide. And I'm going to go ahead and draw the product with a wedge here. All right, so there's an oxygen coming out relative to that plane.

And if we go ahead and name our product, right, so the parent name would be cyclohexane, and our epoxide would form between carbons one and two, so we could go ahead and name this as 1,2-epoxycyclohexane, like that. Let's go ahead and to cyclohexane, let's do another reaction.

Modified heterogeneous silver catalysts are typically employed. Safety considerations weigh on these reactions because organic peroxides are prone to spontaneous decomposition or even combustion. Metal complexes are useful catalysts for epoxidations involving hydrogen peroxide and alkyl hydroperoxides. Peroxycarboxylic acids, which are more electrophilic, convert alkenes to epoxides without the intervention of metal catalysts. In specialized applications, other peroxide-containing reagents are employed, such as dimethyldioxirane.

In addition, if there are other stereocenters present in the starting material, they can influence the stereochemistry of the epoxidation. Metal-catalyzed epoxidations were first explored using tert-butyl hydroperoxide TBHP. Catalysts are required as well. Both t-butyl hydroperoxide and ethylbenzene hydroperoxide can be used as oxygen sources. Illustrative is the epoxidation of styrene with perbenzoic acid to styrene oxide : [11] The reaction proceeds via what is commonly known as the "Butterfly Mechanism".

The reaction is considered to be concerted the numbers in the mechanism below are for simplification. Hydroperoxides are also employed in catalytic enantioselective epoxidations, such as the Sharpless epoxidation and the Jacobsen epoxidation. Together with the Shi epoxidation , these reactions are useful for the enantioselective synthesis of chiral epoxides. Oxaziridine reagents may also be used to generate epoxides from alkenes. Homogeneously catalysed asymmetric epoxidations[ edit ] Arene oxides are intermediates in the oxidation of arenes by cytochrome P For prochiral arenes naphthalene , toluene , benzoates , benzopyrene , the epoxides are often obtained in high enantioselectivity.

Chiral epoxides can often be derived enantioselectively from prochiral alkenes. Many metal complexes give active catalysts, but the most important involve titanium , vanadium , and molybdenum.

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To properly name an ether according to IUPAC rules, identify the shortest alkyl chain attached to the oxygen atom and consider that portion the alkoxy group. Then follow the usual rules for naming molecules, where the alkoxy group is a substituent of the alkane. Another acceptable naming procedure is to write the two alkyl group names followed by the word ether similarly to how we named alcohols, such as ethyl alcohol.

Cyclic ethers have non-systematic names, so we will not focus on this aspect of the nomenclature, but the IUPAC names for several cyclic ethers are given below. Oxolane also goes by the name tetrahydrofuran. For epoxides, the functional group name is epoxy when used in the same manner as, for example, ethyl or methyl that is, following the rules of substitutive nomenclature.

When used in the manner of, for instance, ethyl alcohol functional class nomenclature , the term oxide is used. In the substitutive approach, the epoxy- prefix is preceded by the numbers of the two carbons to which the oxygen is bound. Also note that because of the structure of epoxies, these molecules can exhibit stereoisomerism.

For instance, 3,4-epoxyhexane can actually be either cis-3,4-epoxyhexane or trans-3,4epoxyhexane, as shown below. In addition to cyclic structures such as epoxides , ethers can involve multiple oxygen atoms in a carbon chain. For instance, so-called crown ethers are cyclic ethers with multiple oxygen atoms in the ring.

An example is shown below, along with its simplified name we will not discuss nomenclature for crown ethers. Interested in learning more? Why not take an online Organic Chemistry course? Solution: This molecule is an ether with two four-carbon chains butyl groups attached to the central oxygen atom.

Thus, it can be legitimately called either dibutyl ether or butoxybutane. Solution: This compound is 2,3-epoxymethylheptane. Note that the main carbon chain is numbered as shown below. Synthesizing Ethers and Epoxides As mentioned previously, we have already studied the acid-catalyzed synthesis of ethers from alcohols. Another method is the Williamson ether synthesis, which involves a reaction between a metal alkoxide and an alkyl halide.

For instance, consider sodium ethoxide and bromopropane. The overall reaction is shown below. The mechanism for this reaction involves dissociation of the metal from the alkoxide and then nucleophilic attack SN2 on the alkyl halide. The alkoxide ion acts as a Lewis base with respect to the alkyl halide.

Again, note that this reaction is a nucleophilic substitution involving two molecules SN2. For epoxides, one approach to synthesis essentially follows this mechanism but involves a single molecule in which a hydroxyl group and a halide attached to adjacent carbon atoms these functional groups are said to be vicinal, and this particular type of molecule is called a vicinal halohydrin.

In the presence of a base such as hydroxide ions , the halohydrin donates the proton an acid-base reaction bound to the oxygen atom. Consider the case below of 3-iodobutanol. The remaining molecule can then dissociate an iodide ion as follows, creating the epoxide. The product in this case is 2,3-epoxybutane.

Let's say that between this carbon and this carbon, instead of having a double bond, this carbon actually bonds to an oxygen, which then bonds to this carbon over here. Obviously, every carbon has four bonds, the ones that we're not drawing, those are hydrogens.

How do we name this? Well, same exact process. We actually start numbering the chain closer to where the oxygen is bonded. So we start numbering at this end over here. So this is pentane. The oxygen is bonded to the 1 and the 2 carbons. So we call this 1,2-epoxypentane.

Now, in the last video, I told you that, in general, ethers are fairly nonreactive. They actually make for good solvents. But, what I've just drawn here is a special case of ethers called epoxides. When you just have this three atom chain right here, where it's two carbons and an oxygen. This is a special case of an ether called an epoxide. This is called an epoxide. And this, unlike most ethers, is very reactive.

Another way you could think about it, it's very unstable. This is very reactive. Sometimes people consider these separate from ethers. The reason why they're very reactive, is this three member ring right here. There's a lot of strain on these bonds. These electrons, these bonds don't like to be that close to each other. If you actually tried to make it with an actual model set with molecules, you would have trouble making it bend enough to actually make this bond.

So this is highly, highly, highly unstable. There's actually an alternate way to name epoxides. The alternate way, so this is a completely legitimate way. You could name it just like an ether with a ring. This is 1,2-epoxypentane. But the alternate way is to pretend like you had a double bond here.

That instead of this oxygen here, you had a double bond. If you had a double bond here, this thing would be called, depending how you want to name it, it could be called 1-pentene. That's if there was not this oxygen here, but if there was a double bond here.

This is the 1 carbon. So, 1, 2, 3, 4, 5. This is what 1-petene looks like. We've learned that many, many, many videos ago. Sometimes it's called pentene, depending on which convention. This is the more common one. We have this oxygen here, instead of this double bond.

Instead of calling it just 1-pentene, we call it 1-pentene oxide. Just like that. So both of these are the names for the same exact molecule. This makes it clear that it's an epoxide. That's kind of the special ether that is more reactive.

This is just the general way that we name any type of cyclic ether. So let's just do one more just to make the point clear. Let's have a cycle branching off of a cycle. Let's have an epoxide off of another ring. Just to make the point clear. These aren't too hard to name. But the first time you seen them, a little daunting.

Let's say we have a cyclohexane ring right here. So this is cyclohexane. But let's say we have a little epoxy branching off of it, just like this. We have that going on.

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Nomenclature of Alcohols, Ethers, and Epoxides

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Naming Ethers using IUPAC Nomenclature and Common Names in Organic Chemistry

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