SN1 SN2 E1 E2 Chart (Big Daddy Flowchart) - Video Tutorials & Practice Problems
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Here is the best flowchart you’ll ever learn in your life. Seriously.
Professors rarely tell you which mechanisms to use. Instead, they’ll give you a set of reagents and ask you to figure it out yourself. This flowchart basically explains that entire process. Let’s go!
Determining Mechanisms
When do you use this flowchart? Whenever you have a nucleophile and a GOOD leaving group.
1
concept
Overview of the flowchart.
Video duration:
2m
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Video transcript
So, guys, we have a big problem. I've taught you guys all about s and one s and two e one e two and I've taught you about all the different conditions that are favored for each one. And in some cases, it's kind of obvious what mechanism we would use. But there are a lot of cases where it's going to be kind of blurry, and you're gonna be wondering, Is it gonna be s and two? Is it gonna eat, too? And I remember having this problem as a private tutor back many years ago when I just just used to do private tutoring and trying to put myself in my thinking into my students head and trying to tell them guys, it's just this just obvious. Obviously, the nuclear file, whatever. And what I realized is that it wasn't getting through. I needed some method or some way to just give my brain to someone else so that they would be able to see what kind of mechanism were using. Because many times sometimes we're gonna have to ask ourselves up to four different questions to determine what mechanism to use. So that is when I decided to make a solution. And lo and behold, I'm gonna introduce us to one of the best parts of this whole chapter, which is this awesome Johnny patented flow chart called The Big Daddy Flow chart. And it's just going to change your life. So are you guys excited? Ready to get going? Like I said, this is such a great flow chart. I've even had students that have already taken their M cat in med school. Tell me, Johnny, like the Big Daddy flow chart, still saves my life. So I'm like, Wow, it must be pretty good. So now I've just hyped it up a crazy amount. Hopefully, you guys like it. Let's go ahead and get started. So as you guys can see, it's very complicated. It's very big, but it's actually pretty easy to use The way that we're gonna use this is like a Siris of questions that you ask yourself. Okay, so we're just gonna ask ourselves self, is this whatever. And then you say yes or no? And then you keep going down the flow chart until you get to the mechanism that you need. All right. So what's the most important question It's actually the same question that we were asking when I was teaching about the mechanisms at the beginning, which is, what kind of nuclear file do I have? Is it strong, or is it weak on the way, way? Determine, That is by looking at negatively charged or neutral. So it's actually, it's the same question that we always started off with. So if it's negatively charged, what that means is that we're going to go down the left part of the pathway. Okay, if it's neutral, then we're going to go down the right part of part of the pathway. How it if it's positive, that's a trick question. Positive charges are not nuclear follows those air Electra files, right? So it could never be positive. But it could either be negative or it could be neutral, alright.
In general, the left side of the flowchart predicts SN2 /E2 mechanisms, and the right side predicts SN1/E1 mechanisms, but there are exceptions.
2
concept
How to predict SN2 and E2 mechanisms.
Video duration:
9m
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Video transcript
So let's go ahead and go down the negative part first, because that's actually the more complicated one. Let's just get it over with. All right. So the second question that I asked myself once I've determined that it's negative. Oh, by the way, I'm sorry. There's something that I forgot to tell you guys. There's gonna be some negative nuclear follows that don't look negative at the beginning. Okay? And that's because they're attached to a spectator. Ion. Do you remember what spectator ions are? They're just ions that associate in solution and don't participate in the reaction. So spectator ions. There's actually four of them there in the first column of the periodic table. And there's four that you should be aware of. It's we have lithium. Okay, Lithium associates in tow. Ally Positive. We have sodium, we have potassium. And then finally, we have cesium, which doesn't always show up, but sometimes it does. Okay, thes air. The four cat ions that are going to associate from our nuclear falls and make them negatively charged. So, for example, if I gave you, I'm just gonna tell you there's a really Communistic that's made if I gave you the the nuclear fall Any Ohh. Guess what's gonna happen. Ah, lot of students are going to say that's neutral, but obviously that's not neutral, right? You have to disassociate the any first. And what you're gonna get afterwards is O H minus that is negatively charged to go down the left hand side. Do you guys see? See how to use that? So watch out for the Spectators, okay? They're there to make your life just a little bit more complicated. Now, let's go to the second question. The second question I ask myself is Okay, I know that I have a nuclear file that's negatively charged and what's strong, but is it a bulky base? Okay, um, and for this question, we're just gonna memorize three bulky bases. All right, these are just three bulky basis that I've seen professors used. There really isn't a very long list of them. Okay, Eso really? If you just memorize this list of three, you're set and all it is his terp. You talk side, which is this one l d a. And l I t m p thes air. The three bulky basis that you could find And what you might even notice that your professor might not use all three. Okay. Ah, lot of times, professors will have, like, a pet base that they really like and a little stick with it the whole semester. So, for example, some base some professors love L d A. They just l d a everywhere. Some professors love turkey toxin sure protects it everywhere. It just depends on which professor you get. So I would just say Just know them just in case. Also, in case you ever wanna look up this stuff online or do some more reading in your book, you want to know what the other ones are. Even though your professor might not use it very often. Cool. So those are the three that we say They're bulky, and if they're bulky, what did we say about nuclear files? If I have a very bulky nuclear fault, is that going to be a good base for a bad base? That's gonna be a really good base. Remember that. I said that bulk increases basis city, so that means that automatically right away, we know what the mechanism is. We know that it's gonna be a really strong base So it's gonna be e to Isn't that easy? We're just gonna say, Oh, this is e to right away. Now notice that it has a word Hoffman next to it. Don't worry about that yet. We haven't gotten there yet. This flow chart not only works for this topic, but it works later on as well. So we're going to get there in a little bit. So that would be if we said yes, that it is bulky. Okay, now. But what if it's no? What if, like, for example, o h negative? Is that one of the three bulky bases? No, it's not. So that means I keep going to now, the next question, the next question is questioned. Three. So you can see you've already asked ourselves two questions. We're onto the third one. The third one is what type of leaving group dough I have. Okay, so remember that leaving group could be a lot of a few different things. Usually that's gonna be an alcohol. Hey, lied. But that could also be a sulfa. Nay, Esther. Right. Okay. And then we also said water, but yeah, water, too. Sure. So we could also be water but water doesn't happen quite as much. So I'm just gonna put here. Okay, so there are three main leaving groups. So on now, the way that way have to think about these leaving groups is we want to separate them into two categories. There's the leaving groups that have a good backside. That means there really accessible. It's easy to do a backside attack, and then we have the nuclear files that have a bad back side. So if you have to think about the types of nuclear falls that have a really good backside, what would you think? What would you say? Very available, very down for backside attack. That would be methylene primary, right? Because they're like, have no Starik bulk back there. So it turns out that methylene primary are always gonna pretty much give us the same mechanism because they have a good I'm just gonna right here. Good backside. Okay, so we get a s n two reaction, everything that went along with us and to you think of it that's gonna be for methadone, for primary. Easy. Right. But now we think about the secondary and tertiary is the secondary and the tertiary which are right here. And here are the ones with bad backsides. Okay, they aren't as good. In fact, tertiary is impossible. Secondary can happen, but it's kind of bad at some cases. So for secondary and tertiary, we're gonna have to ask ourselves another questions. This brings us to the fourth question. Let's start off with secondary first. Okay, So now for secondary, What I wanna ask myself is, okay, this nuclear file, that's it's negatively charged. It's not bulky. What I wanna know is, is it gonna be a better nuclear file? Is it gonna be better donating electrons, or is it gonna be a better base? Meaning that it's better pulling off protons. Okay, For this part, all I want you to do is memorize the good basis. Why? Because it turns out that there's probably 20 different nuclear follows that your professor could use. Okay, lots of different ones. He could basically put anything with a negative charge on it and say, that's a nuclear file, okay? And for you, as a student, that could get very confusing, trying to memorize every single nuclear file and what it does. Okay? So instead of memorizing every single nuclear file. Let's just memorize the ones that are good basis, because that's so much shorter list. And then what that means is that anything that's not on my base list I'm gonna automatically soon is better at a nuclear being a nuclear file. So what are these bases that are strong bases? The bases are one oxides. That means any any molecules that I have O r. Negative. Okay, so that's the first one. The second one is called an Alka nine and Alcon. It is just a triple bond with a negative charge at one side. Okay, that negative church has to be directly on the sea. That's also a very, very strong basis, Not very stable. Okay, then we have two bases that are very similar, which is N H two negative and h negative. These air both going to be small, very strong basis because they're not very stable in solution at all. And then finally, we have one more thing that's not really a base, but it favors basic reactions. And that's heat. Okay, It turns out that heat, um, is going to favor elimination for a variety of reasons. Okay, So these five things are things that I want you guys to memorize as favoring an E two mechanism on a secondary alcohol. Haley. Okay, if you have one of those five things or even more than one of those five things, then for sure it's gonna be e to Now, what's this word next to it? Zaitsev again? Don't worry about that. We're not gonna get that. Get to that until the next topic. Okay? Or until a few topics from now. Okay. But right now, you should just know that it's e to. All right, So now what if I gave you a nuclear fall that you really don't know what it is. For example, if I gave you something, Looks like this. And double bond n double bond n positive. Negative. All right, so what if I give you a nuclear file? It looks like that. Okay. I'm sorry. This is supposed be a negative, too. So then after you just, you know, this is actually called and three negative. Okay? If you added up all the formal charges, it would be negative at the end. And I gave you n three negative on a secondary alcohol. Hey, lied. Okay, so my question to you is what would the nuclear file be and what would the mechanism be? And I would just ask myself, Okay. Is n three negative on my base list? Is it an oxide? No. Is it an AL? Can I know? No, no, no. There's no heat. So that means it must be in my nuclear fall category that it's not a good base, and that's gonna be s into and that's going to apply for a lot of different nuclear files. So also, like, for example, s h negative. Okay. S h negative. Not on this list. Right? So that means it must be a better nuclear following. Its gonna do sn to do you guys get the point? Okay. So, basically, I'm just gonna go with whatever those bases are. That's e to If it's not on that list, it's gonna prefer s and two. All right. Are you guys cool with that? Awesome. So now let's go to tertiary. So for tertiary Oops. Sorry. So for tertiary, we get a similar problem where we need to figure out if it's a nuclear fall or a vase. So now for the base list, it's actually gonna be the same as the other list. So the same five compounds, Except that now I'm gonna add O h negative to the mix. Okay. Okay. So o h negative was actually not on my list before because my list before as strong bases it only had oxides. O H negative is not an oxide could. It doesn't have a our group attached to the, uh oh, that's a hydroxyl It's not. It's hydroxide. It's not on. It's not an oxide. So But now I'm going to treat the hydroxide as one of the strong basis. So it's actually gonna be those five things I told you, plus O h negative are gonna favor e to okay.
Here is a list of some more bulky bases that some professors like to use. Be aware that this is not a comprehensive list!
You may also see NaNH2 and NaH (small, non-nucleophilic bases) react via an E2 for primary leaving groups, so keep that in mind!
3
concept
How to predict SN1 and E1 mechanisms.
Video duration:
6m
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Video transcript
Oh, Then what I wanna do finally, is I'm not going to do this last pathway. I'm going to say that one for the end. We're done with the negative one. For now. Okay, Now I want to go to the neutral pathway and then finish up with this last little stick. Okay, so let's go to the neutral pathway. Now, I know that was a mouthful, but now I have to do the neutral pathway. What if we have something like instead of O H negative? How did we just have water? Okay, Waters neutral. Right. So now my second question is, actually, this pathway is a lot easier. All I'm gonna ask myself is Okay. What type of leaving group do I have? Because if this is a neutral, then that's gonna prefer what kind of mechanisms that's gonna prefer that it's gonna be mechanisms that aren't by molecular that don't have the nuclear fall attacking at the beginning. So this is gonna favor S n one e one mechanisms. Right? Because it's going to be waiting around for a carbon Catalan to be generated. Remember that first step? So then I just have to ask myself two things I just have to ask or one thing. Actually, for the second question, I'm gonna say, what type of leaving group do I have? Do I have a leaving group that could make a good car, broke a tie in in the first step? Or do I have a leaving group that wouldn't make a great car broke again in the first step? Okay, so it turns out that if you're leaving, group doesn't make a good car broken in the first step. That would be what type of alcohol? Hey, light Well, remember that primaries and methods are really bad at making Carvel. Katyn. So I'm going to stay here Bad Carville, Catalan. Okay. The two mechanisms that are good at making Carvel Catalans because there's a lot of our group, so it's going to stabilize it. Remember that I said our group stabilize Carvel. Catalans would be secondary and tertiary, so these would be good Carvell cabinets, okay. And the mechanisms really just going to determine on which side you land. If you're on the bad side, that means that you have water, water or whatever. Neutral neutral fault can't do shit. Really. It's just stuck. There it's not very strong. And then it's waiting for the first step. The rate determining Steptoe happen to make the Carvel Catalan right. But then metals and primaries make terrible carbo Acadian. So guess what happens. Nothing happens. So what happens is that the end result is just no reaction because you have a bad nuclear file and you have a bad leaving groups. So it's just the combination is just bad. So overall, you get nothing happening. But what if you have a good leaving group? How it if you have one that's going to be able to actually make ah, good a good a good molecule that could make a Carvel Catalan like secondary tertiary. Then that's where you're gonna favor s and one in E one. Because now you have that good Carvel cat. Um, that you could make the new neutral nuclear fall can attack it and the reason you get s and one and the one is because guess what they compete with each other. So whenever you get A s and one mechanism, you're also gonna get e one competing at the same time. Because the environment that favors S and one is also favored for anyone. Are you guys getting that? So we could never really separate the two. Now there is one thing that we could do. Thio make it favor one over the other. And that is heat. Okay, so I'm just gonna put your heat can favor e one. Okay, so that's true. Like, for example, if I ran it with these conditions were had a neutral nuclear file. Ah, tertiary alcohol. Hey, lied. And then I've jack up the heat like 50 degrees Celsius. Then that can favor e one over s and one. But you're still going to get a mixture of products. It's just you're gonna get a little bit more e one. Okay, cool. So now I want to talk about this last direction, which was How about if I am? I'm sorry about that again. How If I'm in the tertiary position and I want Thio and I don't have a good base, basically, I have a base that isn't good at pulling off protons. What that means is that this one this nuclear fall wants to do an s and two okay, because it's not good at pulling off protons. So let's say something like I negative. Okay, I negative is a molecule that is not very basic. Oh, it's a pretty good nuclear file, but it's terrible base. It was very bad at pulling off protons. Okay, so it's not on my list, right? It's not on my list of five. It's not always minus. So that means that it wants to do in s and two. But it can't because the backside is totally clogged up. So instead, it's gonna have toe wait around for a carbon Catalan to be generated just like a week nuclear file would have had to do in s and one anyone. So you wind up getting S n one e one from this situation. Okay, so I'm explaining the logics that you guys will understand where this flow chart is coming from. But guess what? The coolest thing about this flow chart is that you don't actually need to understand it. And I know that's kind of like blasphemy for me to say that you don't need to understand it, But in the end of the day, you guys just want to do really well in your test, right? That's that's why we have clutch and I want to be clutch for you guys. I just want you guys to memorize this flow chart. If you can understand it, awesome, even better. But in the event that maybe your test is in two days, whatever. I don't need you to know every single detail. Why this? Why that I just need to memorize What are the good bases? What is the What is the different pathways for primary, secondary Tertiary, If you know that, how do I tell us of the neutral or negative? If you know those things, guess what? You could go into your test not knowing much about why this flow tried, exists and still get every single mechanism, right, Okay. And that's because, remember is the flow chart and you know how to use it. So what that means is that for the rest of all the practice problems you do for this course, the ones that I give you the ones that you have to do online, the ones you have to do in your book Whatever you dio, make sure you have this flow chart next to you when you start using it to determine what mechanism you're using because guess what? On your test, your professor isn't gonna be so nice and tell you draw all the products for the E two reaction. No. Guess what? They're gonna let you figure that out on your own because you're supposed to know what mechanism it is, how well you're supposed to be a genius. But in the case that you are in a genius, that you could just use this flow chart, and it's gonna work out pretty well for you. All right, so I hope that that made sense. I do expect you guys toe all. Try to memorize this at some point. But the best way is just through practice. Use it like an open book tests and do all your practice problems with this flow chart in front of you. And eventually you'll have it memorized. Alright, guys. So that's the end of that topic. Let's go ahead and move on.