For each of the compounds described by the following names,1. dra...

Question

For each of the compounds described by the following names,

1. draw a three-dimensional representation.

2. star (*) each chiral center.

3. draw any planes of symmetry.

4. draw any enantiomer.

5. draw any diastereomers.

6. label each structure you have drawn as chiral or achiral.

c. (2R,3S)-2,3-dibromohexane

d. (1R,2R)-1,2-dibromocyclohexane

Accepted Answer

Hi everyone and welcome back to organic chemistry today, we will be considering these two molecules. First drawing their three D. Structure from the given name, then drawing there in Antium and finally drawing any customers? Let's begin with our first example to our three S 23 D. Chloral hexane. First we need to draw the parent chain of the molecule which in this case is hexane. Second, we need to add any substitue ints. In this case we have two chlorine atoms, one of the two and one of the three position third. We can go ahead and fill our molecule in with hydrogen, completing the octet on each of our carbon atoms. And finally we need to consider any Cairo centers. Does this molecule have any Cairo centers? Yes, it does. Each of these carbons bonded to a chlorine atom is a caramel center. So we need to make sure to draw this molecule in the to our configuration and the three S configuration. Let me go ahead and draw this as it should be now and then we can discuss the three D arrangement around each tyrell center There as I've drawn it, this molecule is now in the two R 3 S configuration. Recall that. To visualize the rns configurations. The lowest priority substitue into needs to be facing away from you or into the board. So I encourage you to try to visualize our hydrogen atom are our lowest priority substantially facing away from you and into the board and confirm that carbon to is in the R configuration and carbon three is in the S configuration for now. you can just take my word for it. But the second example will be easier to visualize. Now, do we have any plans of symmetry in this molecule? It looks like we're close but because of the mismatch between the length of these carbon chains. No, we do not. Now we can go ahead and flip this molecule across a mirror plane to draw. It's an anti armor there. We've drawn the molecules in Antium Now if the an anti armor is the perfect mirror image of this molecule, meaning that each of the two Cairo centers is perfectly mirrored. The day history involves mirroring just one Cairo center. So let's go ahead and draw the to die astronomers now. So as I said, for the first day history, um er we will flip the first Cairo carbon and keep the second Cairo carbon the same, keeping the second Cairo carbon, Carbon three the same, flipping the first. And for our second dia Stermer will keep the first Cairo carbon the same and flip the second Cairo carbon there we have produced are to die astronomers finally, are these compounds Cairo or a Cairo. Well, we already identified that each of these molecules has to Cairo centers. We also saw that are starting molecule does not have any planes of symmetry and therefore none of the rest of our molecules should have any plans of symmetry either. So having Cairo centers and no planes of symmetry means that all four of these molecules are Cairo. Now, let's consider our second example. Our second example is this molecule one R two, R one to die chlor. Oh, cyclo hexane. We'll proceed with this problem the same way that we did the first, first we can draw the parent chain of the molecule cyclo hexane. In this case then we can add any substitue ints we're told that we have two chlorine atoms at the one and two position should be a comma there third. We can fill in, hydrogen is completing the octet on each of our carbon atoms. And finally we need to consider any Cairo carbons. Are any of the carbon atoms on this molecule Cairo. Yes. Both of these molecules are both of these atoms are Cairo. Now we can draw this molecule with the correct 3D arrangement around each of our Cairo Carbons. Now, I told you this example, it would be a little easier to visualize the configuration around each of our Cairo carbons. And that is true. That's because in this molecule for carbon one right here are hydrogen is already pointing away from us into the board. So to visualize the our configuration, we can start from our highest priority substitue into go around to our next highest priority substitue into this carbon and go around again to our final, lowest, highest lowest priority substitue into this carbon. That is an our configuration. Now I encourage you to, in your mind rotate this molecule 180 degrees so that the hydrogen on carbon two is facing away from us into the board and confirm that carbon two is indeed in an R configuration, which it is. Now let me go ahead and clean this up a little bit so we can draw our own anti american to draw an anti armor again, we will just reflect this molecule across the mirror plane. There. We have reflected our molecule across a mirror plane, producing the an anti armor. Now for the diocese again, same as we did above to produce the diastolic murmur, we will flip just one of the Cairo carbons. Substitue ints keeping the other the same. Let's go ahead and do that. Now, if we first flipped the substitue ints on carbon one, we'll wind up with a molecule that looks like this. And if we flip the substitue ints just on carbon to keeping carbon one. The same we'll wind up with this molecule there. We produced our two customers. Now, do we have any planes of symmetry in these molecules? In our original molecule? No, we do not. But in our to die astronomers. Yes, we do. We have a plane of symmetry running right through the diastolic murmurs, possessing a plane of symmetry indicates to us that our di astronomers are a Cairo lacking a plane of symmetry and possessing to Cairo centers are original molecule and are an anti armor. Our Cairo there, We've drawn our two molecules there, an anti MERS and there die astronomers. Thanks for watching.

Key Concepts

Chirality

Stereoisomers

Planes of Symmetry

Watch next