Acid-Base Extraction

by Jules Bruno
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in this video, we're gonna take a look at an acid base extraction. Now, we're gonna say, whenever you do an acid base extraction, typically it is better to add a week base before a strong base. That's because the most acidic component will react with that weaker base. If we were to use a strong base from very beginning, all the acidic compounds would all react with it. And in that way, we wouldn't be ableto thoroughly separate them from one another. So we're gonna say this allows us, allows you to Onley, isolate the strongest acid, and that one will become negatively charged and therefore become Equus on become soluble in the acquis layer. Now, here I'm giving us different compounds and with them, their PKs. Remember, the lower your p K is than the stronger the acid. This is gonna require you guys to know some basics about acids and bases, so make sure you've looked at my videos dealing with acid based identification. Now, if we take a look at these we have here, this first compound is called propane. It's PK is 60 so it's pretty high. Next we have methyl amine, which is 10.64 Next, we have what's called fennel. You write them all down. You don't need to know how to name them. I'm just giving you the names for them. And then we have acetic acid. Finally. So the lower your p k, the more acidic you are, we can see that acetic acid has the lowest peek a present. So it's gonna be the most soluble now here. At the moment, they're all found within the organic layer of your secretary Funnel, right, Your secretary funnel not the best draw. But hopefully you guys understand what I'm writing. So what we have here is our organic layer, which has all four components in it. And then below that is our acquis layer, which is more dense, heavier. That's why it's on the bottom, right? So in the organic layer, they're all neutrals, So they're all going to be found in the non polar organic layer. What you're trying to do is react the solution with an acid or base at each step. This will cost some of the compounds to gain charges. Once they gain a charge, they're gonna slipped down into the acquis layer because the Equus layers polar, and when you gain a charge, you become polar. And once they're in the acquis layer, we can drain out that acquia slayer and separate that component from the rest of them. Then all we do is we re ADM. Or Water, which will naturally seep down to the bottom and do the process over again. So here what we do first is we react these four guys in the in the organic layer with 40.25 Mueller sodium bicarbonate, which is just baking soda, which is weakly basic. So this would react with the strongest acid present, and the strongest acid present is the acetic acid. It would react with the base so it donate an H plus to the base and become my acetate ion. So here goes your acetate ion. It's now in the acquis slayer because it's came to charge, and then the remaining guys here. They're not as acidic, so they won't react with the sodium bicarbonate. So they're still in the organic layer. Yeah, now here in the Equus layer, that's and we want to make it a solid solid within that equals layer. At the moment, it can't be a solid because it's charged and making it polar, so it'll dissolve in a polar solvent. What we have to do here is to take away its negative charge and we do that by giving back it's H plus. So we use some acidified water. So this is acidified water that acidified water, which is donating h plus to this, making it neutral again. And now it would exist as a solid in the aqueous layer. Now we've got to continue. So we've gotten rid off the most acidic component out of the four. Now we have these three remaining, so now we're gonna use a stronger base. So use sodium hydroxide. That stronger base will react with the next most acidic compound, which is the fennel it takes away. It's H plus, So becomes C six h +50 negative. We don't take away one of these here because those air connected to carbon and carbon hydrogen bond is not very acidic, so they'll stay there. We're always seeking hydrogen from either end. This h technically is not connected to the carbon. The formula is deceiving that hydrogen is actually connected to the oxygen in fennel. So here we get our Fenno late. I on it has a charge. So now it is in the Equis Slayer. And because it's in the acquis layer, it's gonna be polar. But we need to make it neutral again. So again we use acidified water which is gonna donate an H plus to the fennel late on an ion and give us back fennel. It's neutral again, so it becomes a solid within the nucleus layer. So what do we have left? We have left our propane and arm, Ethel Amine. So if you recall my videos on identifying acids and bases, remember that compounds made up of only carbons and hydrogen are non polar. Therefore they're not acidic or basic, so this is always gonna be found within the organic layer. So there's nothing we can do about that. And then methyl amine in the name we hear the term a mean. Remember, if you're a neutral amine, meaning you have no positive or negative charge. You are a week base because you are a base. You will react not with the base, but with an acid. So we switched up a little bit here instead of using a base. Now we're using an acid that HCL will donate in h plus to the methyl amine. And here becomes C H three and H green positive. So becomes method ammonium I on. And because it has a charge, it's gonna be in the aqueous layer. Okay, but here now we take a look. They're gonna use acidified water. What we're gonna do instead, Actually, we're gonna use O h minus. Gonna use some base. The base will rip off. Ah, hydrogen. Here it's gonna accept an H plus so that this can become neutral again. And now it's gonna be a solid in the acquis player. So this is how we perform an acid base extraction. It allows us to separate different solids from solvents by introducing a new solvent again. It's hard to do this if you don't understand the principles of identifying acids and bases in which we talked about. So make sure you take a look at the chapter when we talk about acid and base is how do we identify them as being an acid or base, weak or strong? What is Ah, high K a mean what is a low p k mean the higher your K a. The stronger the acid, the lower your PK, the stronger the acid. This all these things built up in terms of being able to do this laboratory technique in which we use different pH is and different affinities towards acids and bases help separate solids from a liquid.