Alkynide Synthesis

All right. So this is a pretty easy example where I'm already starting off with a triple bond. So half the work has already been done for me. All I really need to do is dip rotated because notice I have a terminal Al Kaine already. Okay, so I don't have to worry about making a triple bond, which is a more advanced part of synthesis. Already have the troll bond. All I need to do is wrecked it with a strong base to get that h off of it. And that's what I'm gonna do in my first step. So my first step is NH two negative. I'm gonna grab that h and I'm gonna wind up getting an Alcon. I'd Okay, so the Alka Night synthesis is the first part. I'm gonna go ahead, draw that Alcon eye down here, and what it's gonna look like is just the same thing with a negative. Okay, Now I react that Alcon I'd with a leaving group, and in this case, it's a primary leaving group. Okay, what do I get when I get a reaction between a strong nuclear file and a primary leaving group? Well, this is the kind of question that we would use my flow chart for, because any time you have ah, leaving group and a strong nuclear file, that's a perfect flow. Chart questions. So you guys might already know the mechanism, But I'm just gonna go through this again in case maybe you forgot, by the way, this flow chart that I keep talking about It's something that I introduced in the substitution and elimination chapters. Okay, so if you're wondering about this flow chart, just go ahead And, like, look at those videos because we're using that flow chart for a lot of different things. Okay, so basically on by, by the way, I will include a copy of the floater in this lesson so that in case you didn't see those, you can still get the copy of the floater in this lesson. Okay, but instructions on how to use the flow chart are gonna be in those other lessons. Okay, so basically, um, what we've got is a negatively charged nuclear file, so I would be on the left side of the flow chart than to what we have is is it a bulky base? No. So then I would keep going to three. What kind of leaving group? So I have primary, so that equals s and two. So this is gonna be an s and two mechanism. Okay, So I would go ahead and draw my I'll kill. Hey, lied. And I would do a backside attack. And what that's gonna give me at the end of the second step is now a triple bond with an ethyl group on it. Okay, So, as you can see, I just made my molecule bigger. Now, this last step is a re agent that you are supposed to be able to recognize. And this comes from the hydrogenation section. This would be Lynn, Lars Lynn, Lars Catalyst. And you guys remember what Lynn Lars catalysts did to triple bonds. It turns them into cysts. Double bonds. Okay, so I don't need to know the mechanism for this. All I need to know is that this is going to become this double bond and then Ethel, So notice that now both of my large groups are on the same side of that double bond making it sis. So congrats, guys. You just did your first multi step synthesis. There's gonna be a lot more to come in terms of you have to do your own practice. But I'm just trying to show you a really common synthetic pathway. Now, this next one is also very common. Go ahead and try your hardest, and I'll go ahead and give you the answer. Okay, Go for it.

So this question starts actually, one step further back on the synthetic process, Where in the previous example, you had a triple bond. But in this example, you aren't even starting with the triple bond. So we're gonna have to make the triple one first and then reacted with everything else. Okay, so let's go ahead and look at this. So I have a double bond with I to do You know what happens when I react Any type of diatonic halogen with a double bond? It's a reaction that we learned from the addition section of organic chemistry. This would actually be a reaction called a halogen nation. Okay, now, if you don't remember what that is, that's okay, but you do need to know it. What it is is basically that you would get to visceral hydrogen e mean to divisional ha logins together. So, um, if you guys remember, the mechanism was just kind of like this, I'd have a double bond. I and I and I would do these three arrows where one arrow ghosts, the i one arrow kicks out the other eye and one goes back. So what I would wind up getting is a bridge like that, and then the other I would come in. I negative would come in and attack. Okay, so at the end of this whole process, what I wind up getting is iodine and iodine. All right, so it's the first. That's the end of the first step. This is the halogen nation step. Okay, so now I have a vis inal die. Hey, Light, that's what this is. And do you guys know? Anyway, to go from visceral day? He lied toe a triple bond, cause that's what I'm trying to do. I'm trying to make triple bonds and, yes, remember that we can take this. It'll die. Highlights or genital diet highlights, and you can react them with excess base to give us triple Barnes. Not only that, we can react them with three equivalents of base to give us Alcon eyes. So how does that work? Well, I would take this and I would react it with two equivalents of base, which, in this case, is gonna be h minus. And what that's gonna do is it's gonna do a double elimination, so I'm gonna wind up getting a triple bond like this. Okay, then I would take one more equivalent of H minus. And that would take off the acidic h there and make in Al Qaeda. Okay. Are you guys following so far? Now, you might be wondering, Johnny, where you getting all these equivalents from? Because it says, like, two and one. I don't see that anywhere in my re agents. Well, guess what excess means That it just means use as much as you want to get to the very end until you can't go anymore. So for example, this falcon I'd can't be reacted with NH anymore, so that would be done. Okay, So excess, really, it's just another way of saying three times in this case, okay? It's not got my Alcon. I'd I'm gonna react that with fennel. PH means fennel, ch two I and that's gonna be what kind of reaction this would use the flow chart. Okay. And according to the flow chart, this would once again be s and two because of a primary alcohol. Hey, lied. And a strong leaving group. So I'm gonna go ahead and do this and that. I'm sorry. I said strong leaving. I met strong nuclear file, okay. And what I'm gonna get. I'm just going to school. I can't really school anymore. But what? I'm gonna wind up getting withdrawal really small. Oh, it's gonna go on my head. So I'm just gonna draw on the other side. It's gonna be a triple bond with now a ch two and a benzene. Okay, so that's the end of the third step. Now, my fourth step, what kind of re agents are these? H two and a nickel catalyst. It looks somewhat similar to the Lin Lars Catalyst, but this is a different type of hydrogenation. This is catalytic hydrogenation, okay? And with catalytic hydrogenation on, it's gonna zap the entire thing. So instead of getting a triple bond, I'm just gonna get a single bond. So I say, this is how maney carbons 12345 My final product should just be a five carbon chain and of benzene ring. And that's it. No, sis, no Trans nothing. Because all it is is an alcohol group at this point. Okay, so this is again Ah, very common synthetic pathway. And one that you should expect to see on your test. You should expect to one use sodium Alcon eyes, toe attack. Other are groups through s and two that's granted. You need to do that. But secondly, you need to know how to make Alcon eyes by by using a halogen nation reaction on double bonds just like this. If you want, watch this video five times because I'm guaranteeing you this is gonna be 5, 10 points in your exam. You're gonna need to know how to turn a double bond into a triple bond. Okay? And you're going to do it through these regions, a holiday nation and then a bunch of reactions of base. And that's gonna make a true upon if it's a terminal triple bond. It would actually make an Alka night because it can pull off the age. Okay, cool. So let's go ahead and move on.

So let's get started. In fact, there's so much to this problem that maybe it's best that I coach you a little bit and then you even try one more time just to see if you can get it. So here, notice what I'm starting off with is a double bond. Okay, starting with a double bond. And what I'm getting is a brand new carbon group. So I start off with four carbons and end up with five. Okay. Just so you know, the Onley way that you know how to add carbon carbon bonds right now is through sodium Alcon eyes. Okay, So do you organize? Remember the triple bond with a negative can attack and Al Kyohei lied. Okay, That's the only way that you know how to add our groups. So what that means is that you must be thinking you have to be thinking here. How can I make this double bond into a sodium alcon ID so that I can add that extra metal group? Because if not, you're totally stuck. Okay, So what I want you to dio is actually pause the video and see if if you were on the right track then just confirmed. But if not, see how you can turn that double bond into a triple bond and then reacted with something that's gonna make it look like this, Okay.

Alright. So either you've just given up or you got it right. So let me just coach you through this. So basically, this is starting off as a double bond. I needed to be a triple bonds that I could do the sodium alkali thing. So my first regent has to be some kind of hallucination. So in this case, I'll just use B R two. And what BR two is gonna do is it's going to give me It's gonna give me visceral daylight's. Okay, So I have to be rs what's special about that? Well, now that I have those to be ours now, I could do a double elimination. In fact, not only can I do a double elimination, I could actually just remove the hydrogen of the alkaline in all one step so I can just use any strong small base like any any NH two times three or in excess. Same thing. Okay? And what that's going to do is to equivalents are going to wind up making my trouble bond through double elimination. Okay, then my last equivalent is gonna wind up deep protein ating to make an Alka night. Alright, So notice now I've got my Alka night. I've got four carbons, but I need five. What could I react this with to make it a five carbon chain? Well, what I could react it with is a one carbon alcohol, Haley. Because basically the number of carbons you're gonna have at the end is the number of carbons that your nuclear file has Plus your electric file or basically your nuclear file. Plus, you're leaving group, So I want Thio. Add a one carbon al Kyohei light. I could have used anyone carbon alcohol that I want. I could have used chlorine or bromine. I'm just using iodine for no reason. So let's go ahead now. Do our backside attack. What that's going to give me? Let's just scroll down a little bit. By the way, I should have put that up here. What I was using three is ch three. I okay, if you used another halogen more power to you, I'm You did awesome. Okay, so now I've got my triple bond. Now that drill bond is attached to another carbon. So now I've got those five carbons. I'm actually ridiculously close to the end target. All I need to do is one more thing to make it look like that. I need to get rid of that triple bond. You have no way to do that. Okay? A way to do that is to use catalytic hydrogenation so I could use h two over palladium, catalyst or platinum or nickel. Either one. So I'm just gonna put here h two over my catalyst, and that's going to finally give me my target, which is that cool, right? So this seems random, but it's not random because it's a pattern. This is a pattern that I've seen repeated over and over and over again in exams, in homework, all kinds of stuff. Your professor wants you to know this. So just keep in mind that whenever you're starting with a double bond, you're always gonna be working towards the triple Bond and then towards doing ah, substitution reaction. All right, so let's do it. Go ahead and do another one based on the same principle. Go ahead and really try to solve it yourself. Okay, Now, actually, let me do the coaching really quick. Notice that for this next one. What do what am I starting with? I'm starting with a trans double bond. Okay. And at the end, when am I getting at the end? I'm getting assists. Double bond. Okay. Did I ever teach you guys a reaction that goes that switches these types of double bonds that goes from trans to CIS or sister to Trans? Did ever teach you a reaction that, like, twists the double one? Never. This is not a one step reaction. This is gonna be many steps in order to make this happen. In fact, just a hint. You're gonna have to change that from being a double bond to being something else, and then do that later. Okay? So hopefully you're already thinking I've been kind of hinting that this whole section is about a certain type of molecule. Try to turn it into something that you can later turn into assist double bond, using maybe a certain region. Okay, that's all the hints I'm going to give you. Try it yourself. And if you get stuck, whatever, then on posit and then I'll show you guys how to do the whole thing. All right, So go for it.

I hope you guys gave this a fair shot because this is also very common synthetic pathway. You should know by the end of this lesson how to turn trans into cysts and cysts into Trans. That's a huge part of this chapter, so let's go ahead and get started. Since there's no way to directly turn this into one or the other, I'm going to need to go to the triple bond. First, I'm gonna need to take it up to a triple bond, and then I can hydrogenated to whatever type of double bond I want. So if I'm making this a triple bond, then I'm going to start off with a diatonic college. And again, let's try CL to this time what that's going to do. Is it going to give me visceral die? Hey, lids. Okay, then my second step is gonna be to make this into a triple bond, and I can do that using one of my strong small bases in excess. Now, notice that this is not a terminal triple bond with this is gonna make is actually an internal triple bond where the Triple One is inside of two different carbon groups. so could I ever get an Alka night out of this? Remember, an Alka night has that negative charge? No, because this doesn't even have a hydrogen to remove. There's no hydrogen here. There's no hydrogen here. So when I make when I take my base to excess, I'm just gonna end at the triple Bond. I'm not gonna go all the way to the balcony. So now I have that triple bond. What could I do to make that into a cyst? Double bond. It's not that hard. All I have to do is use Lynn Lars catalysts, okay? And there were a whole lot of other ways to write it. I'm gonna let you guys look that up, depending on what your professor wants. But I'm just gonna write Lindlaw because that's another acceptable way to write it. Okay. And it would be Lynn Lars in h two. There would be aged to somewhere. Okay, H two inland, Lars. And what that's going to give you is that's going to turn that into a Sistol bond. And now you've just made the conversion from trans assists. And now you guys should for practice. Really? Before you get to your exam. You should know how to go the other way as well. To go from CIS to trans. It's not that hard. Okay, so I hope that made sense to you guys. This is just a small taste. At the end of the day, you're gonna have to practice. You have to do homework. But I'm just trying to show you give you hints of stuff that I've seen come up over and over again and stuff you absolutely can't get to your test without knowing how to do. All right. So let me know if that helped. And let me know if you have questions. Let's move on.