22. Organic Chemistry
A molecule that possesses chirality is said to be nonsuperimposable.
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So we're gonna say a molecule is Cairo when it possesses a carbon that has four unique groups attached to it. Now we're gonna say this molecule is said to be non super imposible. That means that you cannot slide it over one another and then be the same. What do I mean by that think of your hands, Your hands are Cairo. So let's say have this hand here and I have my other hand pen, here's my other hand. Now, when we say things are non super imposible, that means I cannot slide them over each other and they be the same. Okay, so right now my hands are non super imposible. I can't slide this hand over this hand and they overlap perfectly. If I did this, of course they'd overlap better. But that's still not the same thing when we say overlap, that means that the same faces are overlapping each other here. It's basically my palm turned this way towards me and my other palm turned this way towards you, they have to both be pointing the same direction overlap perfectly. So what's a good example of things that are not Cairo? If we had two sheets of computer paper, blank paper, they would be able to overlap each other perfectly. Right? You have a stack of computer paper, they can overlap on top of each other perfectly. So we would say that those sheets of paper are not Cairo because they can slide on top of each other. Now you're gonna go into more detail in terms of this. When you get to organic, you just need to understand the fundamentals. So it's basically a carbon that is connected to four different groups. So here's a great example of a Cairo carbon. This carbon here is Cairo because why it's connected to four different things. It's connected to A B, R, and O. H, and H. And A C. H. Three. You literally count each one of these as a group connected to it. Now this CH three cannot be carbon this carbon because it's not connected to four different things. We see that it has three hydrogen on it already. It can't have more, it can't have four different groups on them on it because three of the hydrogen are all the same. So here we're gonna say the mirror image of any carl's molecule is called any nan tumor, any nancy. So basically we can say that this is my car, A molecule A. And let's pretend that it was looking in the mirror. If we're looking in the mirror it would see back its reflection. It's a mirror image. So this compound B is, it's a nan tumor, its mirror image when it looks into the mirror. Now here this is drawn three D. Just realized here that this dashed here, just means that H points into the paper and that this metal points up out of the paper towards us. So it's just three dimensional stuff. Don't worry too much about that. You go into greater detail again, inorganic cam. When you talk about this. But again, this is a great review in terms of understanding the fundamental principles of organic one. That way, when you first see you're not like oh my God, I've never seen something like this before. Now we're going to say that unanimous. Two things that are unanimous mirror images of each other. They have the same connections. So they both have the same carbon. They are connected to those same four different groups. Both are connected to br both are connected to O. H. Both are connected to H. Both are connected to metals. So in an tumors have basically the same molecular formula. Same connections. There just a little bit different because they're mirror images. We're gonna say compounds that fit this criteria of having the same formula. Um Same connections but slightly different orientations. We refer to them as stereo ISIS members. Okay, so stereo A and stereo chemistry means that we're showing wedged and dashed bonds. Now here, if you're not, you're not only stereo but you're also optical sensors. We call you optical because remember optical deals with vision. The thing about Cairo centers, Cairo molecules is that they have a special property that allow them to basically influence the direction that light will um bend in terms of passing through water. We'll see that in the next section on how exactly can a car a molecule affect the direction that light travels. No knowing this. I want you guys to attempt to do this here. I give us a question where says, identify the compound that possesses an asymmetric center. An asymmetric center is just a fancy way of saying a Cairo center. Okay, only one of these answers is correct. And remember a Cairo center is when you have a carbon connected to four different things. If it's not connected to four different groups it cannot be Cairo and an example. D let me just show you example, do you real quick? So here it's drawn as a skeletal formula. Remember in a skeletal formula every end and every edge is a carbon. So this is a carbon, this is a carbon, this is a carbon, this is a carbon and this is a carbon. And remember carbon must make four bonds. So this carbon here is making two. So it's a CH two. This is a CH two, This is a CH two and this is a CH two. And then this is just simply A C. That's making four bonds already. So it has no hydrogen at all. So if you guys got a little bit lost there, make sure you go back and take a look at the videos we talked about when it comes to structural formulas. Being able to read skeletal formulas is gonna become essential when you guys get to organic. But for now, take a look at this question, see if you can find out which compound has a carbon connected to four different things. And when you come back, we'll take a look and see which one was the best answer. Good luck guys.
A chiral compound is a compound where at least one carbon is connected to 4 different groups.
Identify the compound that possesses an asymmetric center
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Alright, guys. So here it says, identify the compound that possesses an asymmetric or Cairo center. So let's go one by one. And see, we're looking for carbon with four different groups. Here's a carbon, but it's not connected to four different groups. It's connected to three hydrogen that are all the same. Definitely couldn't be Cairo next one. Here. This this is a carbon, but look, it has to hydrogen is on it. All the groups connected to carbon, all four of them, have to be different from one another. It's C H two. So two of the group's that's connected to our hydrogen can't be Cairo. Here's another carbon. That carbon is connected to two methyl groups. Those are the same two groups can't be Cairo, and those metals themselves can't be Carl because they're connected to three. Hydrogen is each Here. This is. These two are triple bonded carbons, triple bonded and double bonded carbons are not connected to four groups, so they can't ever be Cairo. There is rare exception where a double bonded carbon could be Cairo, but you won't have to worry about that just yet. You worry about that more organic. So for now just say that if it's a double bonded or triple bonded carbon, it's not connected to four groups. So it couldn't be Carl here. Let's take a look at this one. This carbon here, it's connected to three hydrogen again. Can't be Carl, but look at this carbon here it is connected to an H A, C, l and F, and then we count This all is one thing as a ch three, so that carbon there is connected to four different things. So this carbon is Cairo. So that's a Cairo center. So this is a Cairo molecule. Finally, for this last one here, this is automatically out because it has three hydrogen is that are all the same. These are all automatically out because they have carbons with two. Hydrogen is each same two groups and then this carbon here cannot be Carl, either because it's connected to a ch three a c l cool. That's two different groups. And then it's gonna be connected to two ch two that look exactly the same. But we got to keep going until we find a difference. So, beyond these two ch twos, we have another pair of C h two s and we get to the end of our ring and we never find a difference between both sides. So this carbon here is not Cairo. Even if you didn't know that, you should have seen that, see, definitely had a Cairo center. This carbon here is definitely connected to four different things. It is our Onley Carl molecule. In the next section, we'll see how Carol molecules can affect the rotation or the direction that light travels.
From the previous question draw the mirror image of the chiral molecule
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Hey, guys, let's take a look at the following questions Dealing with practicing Chire ality centers. So here we say from the previous question, draw the mirror image of the car A molecule. So when we first talked about Chire ality, we found out that the Cairo molecule was this molecule. It was a carbon connected to h toe a f toe, a seal appear into a method group of ch three. So remember to be able to draw some things a nan Timur pretend you see a mirror here and this thing is looking into the mirror. If it looks into the mirror, it sees back its reflection. So basically you have to write this molecule and reverse Here, this is looking into the mirror. The H is gonna see its reflection. Then the carbons going to see its reflection with these two hydrogen is on it and then this carbon here with the seal up here and the F down here and the h here, so that would be its mirror image or its finance humor. So again, remember your Anant summer is its mirror image. Now I want you guys to what try to attempt to do this one here and I'll give you guys help in terms of the inversion method, the mirror method, that's just it, looking into a mirror and drawing what it sees now, the version method I haven't taught you yet. Now here the inversion method. All you got to say is you have these bonds wedged bonds and dashed bonds. We call these stereo Kemmer chemistry on bonds. They basically talk about Which direction are those groups pointing? If you're dashed, you're pointing into the page. If you're wedge, you're pointing up out of the page now to draw the you Nancy more of this compound by the inversion method. All that means is you keep the molecule still as it is, and you just invert the bonds, meaning you switch them. If it's dashed, it becomes wedged. If it's wedged, it becomes dashed. This bond here is dashed, so when the inversion method I have to drop wedged, this bond here is wedged, so I have to drive dashed. This pond here is dashed, so I have to drop wedged, and that's all the inversion method is This is just another way for us to draw the Ananta more of a compound. Both methods work. You can either do the mirror method where you pretend it looks into the mirror and draw its mirror image. Or if they show you stereo chemistry, you invert the bonds. If it's wedged, it becomes dashed. If it's dashed, it becomes wedged. Now here, I'll give you guys a little bit. Time to draw the mirror image off this compound, using the mirror method. Come back and see how I get my answer and see if it compares to yours.
An enantiomer is the mirror image of a chiral compound. To draw the enantiomer of a compound just image the compound looking in a mirror.
Draw the mirror images for the following molecule
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alright guys. So if this thing is looking into the mirror so there's a mirror here that it's looking to and it's looking into it. What does it see? It sees its reflection. So this O H. Is looking into the mirror so it sees its reflection back. Basically, the O. H. Pointing right back at it and then this metal sees its reflection. It sees a method pointing back at it. And in here the seal in the back is just like that. So this would say is A and we'd say that these two things are the Ananta more of a there, the mirror images of it we need to do about the mirror method or the inversion method for this one here. When you get thio, biochemistry for those of you are bio majors or decide to doom or chemistry related classes. When you get to biochemistry and learn more about these types of structures, this is a sugar. Okay, so this is just a biological sugar and here you guys can do the mirror method, pretend you see it in the mirror. Now the inversion method when it comes to sugar, things drawn like this, the inversion method. All you have to do is invert these bonds here in the middle. Just gotta flip him the tops and bottoms stay exactly where they are. So here this group is going to stay as it is. And so is this. And all we're gonna do is invert or flip the middle bonds. So this year is gonna get flipped. So oh, each on this side h on this side, on which on this side h on this side and then each on this side of which on this side so that would represent in a tumor where we flip the middle bonds, they're The reason we flip those middle bonds is because those are the Carol centers. These carbons here are connected to four different groups each. Here, it's a little bit more advanced, um, than what's covered in your book. So that's why we're not going into great details in terms of talking about those carl centers, Remember, For a structure that looks like this, it's basically dealing with carbohydrate a sugar, biological, sugar. You just invert the middle bonds and leave the top and bottom alone. Now that we've done that, I'll give you guys a moment or so to draw the mirror image of it using the mirror method. So pretend this molecules looking into the mirror and tell me what is exactly does a c back come back here? We'll take a look at my answer and compared to yours
Draw the mirror images for the following molecule.
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Additional resources for Chirality
PRACTICE PROBLEMS AND ACTIVITIES (2)