Suggest a scheme by which N-methylmorpholine, salicylic acid, ...

Question

Suggest a scheme by which N-methylmorpholine, salicylic acid, and naphthalene can be separated.

Accepted Answer

All right. Hello everyone. So this question is asking us how could molecules A B and C be separated? Now, given the structures of A B and C, there are a few different things we can consider when trying to figure out how to separate them from each other. First, we can think about their relative polarity to start off. But we can also think about other factors such as their solubility in certain solvents like water as well as any acidity or base city to consider depending on what functional groups are present. For example, starting off with molecule A, we can see that molecule A has a carboxylic acid functional group. So because of this molecule A is relatively acidic and somewhat polar. However, it's worth mentioning that it does have a relatively high molecular weight. So because of this, even though it's somewhat polar, it's still going to be insoluble in water due to that high molecular weight. Now, on the other hand, molecule B has a nitrogen atom recall that a neutral amino group, a neutral nitrogen atom could behave as a base. So molecule B is somewhat basic now similar to molecule A molecule B is somewhat polar. However, because of its high molecular weight, it's still going to be insoluble in water that leaves us finally with molecule C which is simply a hydrocarbon. So no polar functional groups which means that it is nonpolar and definitely insoluble in water as well. So none of these molecules are soluble in water. However, we can use a solvent like diho ether before the separation process because diethyl ether is somewhat nonpolar on its own because of the ethyl group surrounding the oxygen atom and the oxygen atom can also interact with the polar groups in molecules A and B. So the first thing that can happen, that's step one here is that we can go ahead and add diao ether to the mixture. We can dissolve molecules A B and C in diho ether in which all of them are going to be soluble. And from there, we can take advantage of the polar functional groups present in molecules A and B to separate those further. For example, after the mixture is dissolved in diao ether, we can go ahead and add aqueous sodium hydroxide. Now, hydroxide being a base is specifically going to react with the carboxylic acid group of molecule A, this is ultimately going to produce a carboxylate salt because the carboxylic acid is going to be detonated. Now upon the addition of aqueous sodium hydroxide, in particular, that's going to create an aqueous layer and the carboxylate salt is going to be soluble in water. So that's going to separate itself from the diet ether. So from there, you can separate the aqueous layer containing molecule A or the carboxylate salt from molecule A from the dial. So at this point in the aqueous layer, we have the carboxylate salt created from molecule A and so in the ether layer, we have what's remaining. So molecules B and C. So this introduces the second step of the sequence because to the aqueous layer, we can go ahead and add aqueous acid, for example, HCL, upon the addition of aqueous HCL, then the carboxylate salt is pronated to ultimately produce molecule A in the neutral state. So now to go ahead and fully isolate molecule A, we can then go ahead and add diao ether once more. This creates another separation between the aqueous layer and the ether layer. So now at this point in the aqueous layer, we have other species, for example, counter ions created from the aqueous acid in solution. Whereas in the ether layer, we have the neutral molecule A. So after diho ether is fully evaporated molecule A has been completely isolated. So now at this point, molecule A has been removed from the mixture. So now we have to separate molecules B and C recall that molecule B was the molecule that contained a relatively basic amino group. So here we can go ahead and add aqueous HCL to the ether layer from the first step that contains compounds B and C. After this happens, then the nitrogen atom of molecule B is subsequently potentate to create an ammonium salt in which nitrogen has a positive charge. This makes it soluble in the ether layer or sorry, the aqueous layer. So at this point, you can go ahead and separate the aqueous layer from the ether layer. So the aqueous layer is going to contain the ammonium salt. Whereas the ether layer is simply going to contain molecule C now notice how the ether layer only contains one single molecule. So at this point, you can take the ether layer, evaporated and isolate molecule C. This brings us to the next step because the amino group of molecule B has at this point been pronated, we can go ahead and add aqueous sodium hydroxide to result in a neutral molecule B. So we can go ahead and detonate that ammonium salt and produce a neutral molecule beat. So from here, we can repeat a very similar series of steps from when we were trying to isolate molecule A because once we've gone ahead and restored the neutral molecule B, we can once again add ether to create two distinct layers. In the aqueous layer, we have other ions created from the acid base reactions. And in the ether layer, we have neutral molecule B which can be isolated after diho ether is fully evaporated. And there you have it at this point. Molecules A B and C have been separated from each other. So I'm going to go ahead and pause the recording so I can rewrite these notes and showcased the final answer. All right. So here I have the procedure described in this video fully written out to display the final answer. So the final answer reads as follows. Step one, dissolve the mixture in diethyl ether, add aqueous sodium hydroxide and separate the two layers for it. Step two A add aqueous HCL to the aqueous layer. Add diethyl ether, then separate the two layers formed evaporate. Die e ether pure molecule A is left step two B, add aqueous HCL to the di ethyl layer. Then separate the two layers formed. Step 38 evaporate the dye eho ether layer. Pure molecule C is left step three B, add aqueous sodium hydroxide to the aqueous layer. Add diho ether, then separate the two layers formed evaporate die eo ether. Pure molecule B is less is left. Excuse me and there you have it. So if you watch this video all the way through to the end, thank you so very much. And I hope we found this helpful.

Suggest a scheme by which N-methylmorpholine, salicylic acid, and naphthalene can be separated.

Key Concepts

Solubility Principles

Acid-Base Chemistry

Extraction Techniques

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