1,4-Dioxane is made commercially by the acid-catalyzed condens...

Question

1,4-Dioxane is made commercially by the acid-catalyzed condensation of an alcohol.

(a) Show what alcohol will undergo condensation, with loss of water, to give 1,4-dioxane.

(b) Propose a mechanism for this reaction.

Accepted Answer

Hey everyone and welcome back in today's video, we are going to solve the following problem. Acid catalyzed condensation of an alcohol gives 2356 tetra missile 14 dioxane. Number one. What alcohol undergoes acid catalyzed condensation to give 2356 Cetra missile one for dioxin And to suggest a plausible mechanism for the synthesis of 2356. That's from Ethel one for Dioxin. Starting with the first problem, we will recall the general reaction scheme for condensation of alcohols whenever we want to make ethers. So suppose we have two alcohols. One of them is R O H unless suppose that another alcohol is exactly the same. So we can say either to governments of these or simply that alcohol reacting with itself under acidic conditions in the presence of asset where essential farming and ether, these two are groups will be bonded to a central oxygen atom. And then we would be releasing a molecule of water because I feel like it's the geometry we are using one of the oxygen atoms. So we end up with additional to Hae Jin's and oxygen atoms. So our by product would be water this is a general condensation reaction and it allows us to understand what kind of alcohol can undergo condensation with itself to produce a symmetrical ether. Right. As long as these are groups are exactly the same, we have a symmetrical ether. Now, let's think about the structure of 2356 detrimental dioxane. Now, essentially as the name suggests, Dioxin would have six positions. It's a 2356 tetra method and then one comma four, we have every position being assigned to some substitution. So we will have a ring because the oxen is a ring with two oxygen atoms and these oxygen atoms are at positions one and four. So we can draw a six member ring. Keeping in mind that positions one and four are oxygen atoms. So this is what we have. So if we start by drawing the first oxygen atom, then this is our position number one, position, number two, position, number three, position, number four. And this is where we have our second oxygen atom. And now we need position number five, position number six. And we are done. So we got one comma four dioxin and positions 235 and six, they have metal groups. So 2356, right. So we are going to add four metal groups. So this is the structure that we're interested in. And in number one, we just want to understand what alcohol undergoes acid catalyzed condensation. The easiest ways to do that is to break the molecule apart with respect to oxygen. But because there are two oxygen's, we will actually have a dial rather than an alcohol. So if you look at the line of symmetry, specifically, you are interested only in the horizontal line, not the vertical one, the vertical one will not allow you to break that carbon oxygen bond, right? And you're interested in breaking that carbon oxygen want to get your ether. So first of all, if you break it apart, and you remember the general equation, you want to make sure that you're adding a wage to the remaining part and hygiene to this part to keep in mind that there's that water molecule and same thing goes here because you have another auction at. Um So in this case, we will have two equivalent dials. If we break it, We can say that this structure can be achieved from the condensation of two dials. If we draw the bottom one, which will be exactly the same as the top, when we can simply state that it would be ohh H O. And then we have these two metal groups, right? So this will be our alcohol. If we take two units of the style, we could treat it with an asset and form the required one common for dioxin. So we can say this is our required dial for number one. Okay. Well done. Now we understand what the alcohol is. We can use the general reaction scheme to predict a plausible mechanism for the condensation. So let's begin, if we suggest a plausible mechanism, we can just draw the original dial. So let's do that. Let's expand one of the alcohol groups that would be oxygen bonded to hydrogen. And we have two lone pairs. Let's indicate the presence of at least one lone pair in the first step of the mechanism because we have acidic conditions. The lone pair on auction gets protein ated. It basically attacks the acidic proton from the asset and we produce our protein ated intermediate. So we can say that this step is called a protein nation stop. And we are now ready to draw that protein ated intermediate. Oxygen. Now has a formal positive charge because it's protein ated, right? And now that we have formed a protein ated intermediate, it's important to understand that because oxygen has a formal positive charge is now a good leaving group. We could produce neutral water as a result of O H two plus leaving. So that would be a neutral water molecule, right? And what we're going to do now, we are going to think about the nuclear attack stuff, which makes sense because it's a good leaving group. And we are trying to form a ring, another molecule of the dial could essentially attack that electrostatic position followed by the loss of the leaving group. So let's see that let's draw another molecule of our dial, the lone pair on oxygen would perform that nuclear attack at this electra filic position followed by the loss of the leaving group. Right? And we are going to form our first fragment where the two structures are already bonded together somehow. And let's see how that looks like we may simply call this as the nuclear attack stop. And now let's carefully draw the outcome. So if we start with the carbon chain, that would be Our four Carbon Atoms. The second one has an alcohol group, the third one has only that metal group remaining besides the metal group, we are now ready to draw. Actually, let's change the perspective of the metal group. Let's actually draw it upwards. So that would be easier for us to visualize because we're actually creating a bond here. Now, so that bond has oxygen as well as hydrogen. And now that oxygen is bonded to carbon. And now we are ready to draw that four member chain right? There will be a muscle group on the right. And then here we have our O H okay. So this is our fragment. We also have to keep in mind that there's a formal positive charge and auction because once again, we see three bonds here and we are ready to proceed because we got another protein ated intermediate. It makes sense that we are going to d protein ate it to make sure that we're getting rid of that acidic hydrogen. So we can call our next step another deep rotation step. And during the deep rooted nation step, we can use water as our base or as our proton except er because if you notice we formed water previously and that water with its lone pair on oxygen will capture that proton and it will transfer these bonding electrons on the oxygen in the form of a lone pair. And that's how we get our intermediate here. So let's retry it carefully. So we are going to add that metal group, the alcohol group right now at this position, we already have our oxygen, this position, right? And now we can say that here we have our old age. They're not yet bonnet, right? So let's enjoy it. Let's throw this bond slightly shorter. So you don't get confused, right? There's not no bond yet. So there will be oh age. And now here we have a methyl group and another methyl group. Okay. So we got our structure and now we're going to think about what's happening next. So we bonded part of it. Notice that we already forming our part of that ether. This is Annie throw group. We need to form another one. And basically what happens in the next step, which is the repetition of the previous steps, we are going to protein eight, another group of alcohol and perform the nuclear attack. And that's how we will get our final answer. So let's look basically looking at this alcohol group or that one, it doesn't really matter which one you choose, you will get the same final outcome. But you can say if you choose this one, you will just protein it at first. So the lone pair on the oxygen will essentially get protein ated by that acidic proton. And you will get your protein ated intermediate once again. So you can say that in the stop, you are performing the protein nation stop. During the protein nation step, we are just going to show exactly the same structure, right? But we are just going to add a formal positive charge with an oxygen because there's one additional hydrant added. So let's draw that, That will be our H20 now because we have an additional hydrogen atom bought it to oxygen. And there is a formal positive charge oxygen, this metal group. And over here as we said before, we can actually change the orientation of it and say that we have Noh here. Okay, well done. So we got our protein eight intermediate. And remember that when we got our protein ated intermediate, we said that there was a nuclear attack stop. But instead of using another molecule of the dial, we are going to perform an interim molecular nuclear attack, meaning the lone pair on this oxygen in particular, well attack the Electra Philex Center over here because it has a good leaving group which is positively charged water. In this case, we can break that carbon auction bond and release neutral water that's favorable for us. And we are forming our ring, right. So in this step, we are dealing with the nuclear attack stuff, we can indicate that let's draw it below nuclear feel like attack, stop. And we already know what we are expecting to see, right? We can control our ring and the only difference will be that the auction Adam and disposition will have a proton. So we control our sex member drain with tea oxygen atoms. However, this oxygen has hygiene and therefore a formal positive charge. And there our four methyl groups, right? So we got our protein ated intermediate. And the last step is the deep protein nation stuff. We don't want to have that acidic proton. And we're using another molecule of what are just as we did before. So that molecule of what it comes in, captures the proton and the bonding electrons are transferred the oxygen in the form of a lone pair. And here we call this the deep protein nation stop, which finishes the mechanism and allows us to get our final product, right. So we got our mechanism. That's the product that we wanted to get. We can review everything that we needed to know here. So for the first part of the problem, we understood that the structure that we want to send the size is one comma four dioxin tetra methyl substituted. And we had to recall the condensation mechanism. So we broke it apart, drawing a horizontal line across to auction atoms because we went to release water from each part, one water molecule from here another from here. And we said we need to use a dial. In this case, there will be two equivalent dials. And as you can see when this dial undergoes acid catalyzed condensation, there are multiple steps which involves the repetition of several steps. Basically, protein nation, nuclear filic attack D protein nation. And once again, protein nation, nuclear attack and deep rooted nation. So six steps, but actually, three of them just repeat themselves in sequence until we arrive at that final structure. So we, we can essentially say that the whole mechanism illustrated here corresponds to our final answer. And indeed, we get our final product. Now, the correct answer to the small culture is question is c however, if you have any questions, don't have states, leave your comment down below in the comments section. And thank you for watching.

1,4-Dioxane is made commercially by the acid-catalyzed condensation of an alcohol.
(a) Show what alcohol will undergo condensation, with loss of water, to give 1,4-dioxane.
(b) Propose a mechanism for this reaction.

Key Concepts

Condensation Reaction

Acid-Catalyzed Reaction

Mechanism of Dioxane Formation

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