Sigma and Pi Bonds

So basically, we have three types of bonds. You have single, double and triple, and what we need to know is just a few facts about each. The first thing is composition, composition deals with Are they made out of single bonds? Pi bonds? A combination? We need to know this. So I already told you guys, what single bonds were you guys remember? It's just made out of one Sigma. Okay, so whenever I say Sigma, it means single single single means sigma. They're the same thing when it comes to just if it's just one sigma, that's a single now, double and triple get a little bit more complicated because remember that I said that it's actually more than one orbital combining. So for a double bond, it's actually gonna be one Sigma's always, because there's still one region of overlap in the middle from the S Orbital's okay, but there are also these P Orbital's and the P orbital's have two regions of relapse, so that means that a double bond is made out of a pie and a sigma or signal and a pie. All right, so overall, that kind of makes sense because the double bond has to orbital's that are overlapping. Alright. And then finally, a triple bond. You could guess. Now this is gonna have three orbit Orbital's overlapping with. That's gonna be a still that one sigma from the middle from the S is. But for a triple bond, now you have two sets of p orbital's on both sides that are overlapping, one up and down and one side to side. So what that means is that a triple bond is made out of one sigma and two pi. All right, cool. So that's the first thing. Now I want to talk about free rotation. Why? Because this has a lot to do with composition. So remember that I said that a bond is just a region of shared space with electrons. So if I just have one interaction in the middle where they're overlapping, is it possible to rotate one of the atoms like I'm doing right now and keep the bond intact? And the answer is yes. If I rotate this Adam, I can still keep this bond together. Okay, so it turns out that for a single bond, since they only have one region of overlap, we're just going to write a big yes, right here. Yes, I have free rotation there. Okay, because I can rotate one of the items as much as I want. It's always gonna have that bond present. Now it's like a double bonds double bonds. They do have that region of overlap in the middle, that one area. But they also have region at the top in the region of the bottom from the pi bonds. So it's gonna look something like this where you have basically electrons overlapping at the top, electrons overlapping at the bottom. If I try toe rotate one of the Adams is that going toe break or change my bond at all And actually, yeah, will. What's gonna happen is that this top orbital, this top region is gonna break and this bottom region is gonna break. That's really unfavorable and really unlikely toe happen. The reason is because remember that I said that when you form bonds, that saves a ton of energy. So what that means is that I'm gonna have to spend a lot of energy in order to rotate and break this bond, and that's energy that these atoms don't have most of the time. All right, So what that means is that thes double bonds are not gonna be able to break. And actually, that's what I want you guys to write for. Double and triple their both not gonna be able to rotate because the fact that if you rotate them, you're gonna have to break them. And it's very difficult to break the bonds just to rotate. Okay, so good. Now, you guys understand the only ones that rotate are the single bonds. Now, let's talk about length. Hopefully, you guys should remember what I talked about with Sigma versus pie. Which one was the longer one? Do you guys remember? Sigma is the longest. So single bond would be my longest. And actually turns out that because the triple bond is matter of one sigma into pie, this one's gonna be the shortest. Okay? And then you could guess that the dole von is going to be like the middle child. All right, so just create middle. Gonna be in the middle. Not quite as long, but not quite a short right now. Let's go on to strength. So I already talked to you guys about this earlier, which of these is gonna be the weakest overall in terms of single, double or triple. And the answer is that the single bond is the weakest. Okay, the reason for that is that there's only one region of overlap that is saving energy. Okay, now, the triple bond is actually gonna be the strongest. Okay, The reason for that is that it has three orbital's that are overlapping, and each one is giving a little bit. It's saving a little bit more energy, and that means that once again, my double bond is gonna be in the middle. So now I want to ask you guys a question, though. Which of the orbital's is the strongest? Is the Sigma Orbital the strongest? Or is the pie orbital the strongest? The answer is that the Sigma I'm sorry, the single bond, not Orbital. The single bond is the strongest because the single bond saves the most energy of the three bonds for the triple. Then the next pie bond would save a little bit less energy, and then the last pie bond would not save that much energy at all, but it would still be a little bit more. Okay, so You know what I can tell it? There's a little bit confusing, so I'm just gonna give you numbers like before. So imagine that your single bond is saving, like, 436 and then your double bond is saving 599. And then imagine that your triple bond is saving like, 6. 50. Alright, so by the way, I'm just making that number up, but it's pretty accurate. So what that means is that the single bond is saving a ton of energy. But as I go up and get make these bonds a little stronger, each pie bond is gonna get weaker and weaker and weaker. Okay, so by the end, I'm only saving like, 50 kg per mole by adding another python. Alright. Does that make sense? I hope that that distinction is clear to you guys. Professors love to trick you on that

Alright, guys. So the answer to this is I like to just go ahead and just write pie pain, signal and pie and counties up. So the easier one toe calculate is actually the pie. Because remember that there are no pi bonds in single bonds. It's only in double and triple. So that means I would have one pie here and I would have to pie there. She has No Why? Because a triple bond has to pirate two pi bonds, and it's all one has one pi bon cool, because that means that I have three pi bonds total. Then how about single for our sigma signals? A little bit more complicated, because remember that every single bond has a single bond, so that would actually be one. I'm just gonna write signals everywhere. aN:aN:000NaN So I have eight signal bonds and three pi bonds. Now, you guys might have been wondering why did I draw signal bonds here and here because of the fact that every single bond, no matter what it is, has it least one sigma. Okay,

guys. So I hope that wasn't too bad. Let's go ahead and write this again Sigma and pi and see what we get. So what did you guys get in terms of pie? That's easier one. And the answer is that you should have gotten four. Okay? Because I have pie pie pie. And then I have one pie there. Does that make sense? Each double bond has a pie. How maney sigma's did you get? It's a lot. The right answer was 17. Okay? And if you go ahead and count each one, what you find is that you'd have, like, I'm just gonna just check them off. aN:aN:000NaN 10 11 12 13 14 15 16 17. All right, so I know that's a huge mess. I was just showing you each one that I count, right? Each one is a new single. Bon thes are very common types of questions that professors like to ask. So it's important that you guys know how to do this. All right?

Rank the following bonds from shortest to longest

• A. 1 < 2 < 3
• B. 2 < 1< 3
• C. 3 < 2 < 1
• D. 2 < 3 < 1