Design an acid–base extraction scheme to separate a mixture of...

Question

Design an acid–base extraction scheme to separate a mixture of the basic amine N,N-dimethylaniline and naphthalene.

Accepted Answer

Hello everyone. And welcome back. Our next problem says, suggest an acid base extraction scheme for the separation of a mixture of the following molecules. In diethyl ether note that N ethyl ale is an amine and is basic while 23 dimethyl nay is an aromatic compound. So as the problem mentioned, the two compounds that we want to separate are n ethyl annale where we have this aromatic ring in which it has subs a substituent, an amine substituent that has a bond from the ring to a nitrogen with one lone pair and a hydrogen. And then an ethyl group attached to that on the other side. And then we have 23 dimethyl Nalle which is this polycyclic aromatic compound, two benzene rings with two methyl groups attached to one of them. So we have both of these compounds dissolved together in diethyl ether. This is not a completely nonpolar sol solvent, but it's we should say sort of mostly nonpolar and it's a pro so we can separate these things by making one of them into a charged molecule. So changing one of compound into a charged molecule if we can also introduce a solvent that's polar and protic, that charged molecule will then dissolve in the water and you can separate this ether layer and this water layer and therefore separate your non charged and charged particles. So I'll say add, we're going to say water is polar and pro to separate compounds. So that would kind of be our first step. Once we have separated those two compounds, we can then simply isolate our non charge particle by evaporating the ether, we can then regenerate the other one back into an un uncharged compound. Add more ether, dissolve it in the ether, separate that from the charged ions evaporate the ether. And we've got our other one, our other compounds isolated as well to make that more clear. Let's kind of do a little step by step reaction here. When we look at our two compounds. N ethyl ale is a basic and so therefore, is a much better candidate to become a charged molecule than our dimethyl nay or aromatic ring. So we're just going to abbreviate this for an ethyl annale. We're going to call it R NH two kind of the most important part here, the lone pair on our end and we're just going to call our naple molecule R. So we're going to start out and draw a little sort of a little box here that's going to represent our solution. And we're starting out with in ET 20 or Diy ether. We have our R NH two and our r to make this a charged particle or charged compound, excuse me, it's a base so I can pretty easily protein it making it going, taking it from an amine to an ammonium salt. So I'll do that by adding an acid. So I'm going to add hydrochloric acid. And then I also need to add water to give it that so that solvent to dissolve into note that in this step, I want to make sure that I don't generate a stronger acid or base than I than the reactant I started with. So now I will have two layers to my solution as the ether and water will separate out in my diethyl ether layer. I'll have my nale compound. I'll draw a line to divide those this box and then my water layer, I'll now have my ammonium salt, which is going to be our NH three plus, there's a positive charge on that now and my counter ion will be cl minus. So now this can be separated into two layers. I separate the layers, all right, separate layers. And I'm going to evaporate my ether. And now I just have my dimethyl nale by itself. So I still have a layer of my ammonium salt dissolved in water. So now to extract it, I'm going to go ahead and add a base to deproteinate it, return it to its neutral state originally of being an amy and add more ether to separate it out and be able to evaporate the ether and isolate Miami. So I'll add a base. So I'll say sodium hydroxide and I'll add some more diethyl ether. And now I'll end up again with a solution with two layers in my ether. I'm going to have my RNH two, which is now neutral and we'll dissolve in ether. And then in my water layer, I have my sodium ions and my chloride ions. So now I've separated the amine from those sodium and chloride ions. So all I have to do in this final step is evaporate the heater from its layer. And I have isolated my N ethyl ale. So that's my acid base extraction scheme. I start with turning one of my compositor charge particle I have a base. So I've protein it to turn it into an ammonium salt because it's an amine by adding hydrochloric acid and water generating those two layers allows me to evaporate the ether from the ether layer and separate out my R compound, my nay my two or three and dimethyl nay. And then I have this water layer with my ammonium salt. I add a base to get back my amine, add water at ether, excuse me. So that Miami now dissolves in the ether layer, my ions left behind the water layer, I can evaporate ether again and isolate Miami. See you in the next video

Design an acid–base extraction scheme to separate a mixture of the basic amine N,N-dimethylaniline and naphthalene.

Key Concepts

Acid-Base Extraction

N,N-Dimethylaniline

Naphthalene

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