Determining the Number of Chiral Centers Question #organicchemistry

追加: 2026-05-22

[00:00:00]10 asks how many chyro centers are present on the following compound. So a chyro center we're looking for carbons that are connected to four different groups. Now this can sometimes be confusing when we draw molecules in line notation because we have implied hydrogens. But remember for every carbon on the molecule however many bonds we can see if that is less than four then we do have implied hydrogens. So let's draw in all of the implied hydrogens.

[00:00:28]Right now, this on the ring, we've got two hydrogen's there. We've got two hydrogen's here. We've got one hydrogen here. We've got one hydrogen here, two hydrogens's there, one here, and three there. And then we have one more implied hydrogen right here on this carbon. So, we're looking for carbon atoms that are bound to four different groups. Looking at, for example, this carbon right here, this carbon is bound to hydroxil and a hydrogen. and then the two directions in that ring that are different because the ring is not symmetrical. So that qualifies as a chyro center. Then we've got this carbon here with a methyl group and a hydrogen. And then again the two different directions of the ring which are different. So that is another chyal center. Then we have this carbon right here where we have the rest of the other portion of the molecule as well as a hydrogen and then the two directions of the ring which are not the same because it's not symmetrical. And then over here we have this carbon where we are attached to bromine, hydrogen, this methyl group, and then the rest of the molecule over here. So these are the four chyro centers. We do have C four chyro centers. All of the other carbons do not qualify. We've got three identical hydrogens. That doesn't work.

[00:01:46]This carbon, we only have three groups because two bonds are to oxygen. So that doesn't work. And then all of these guys have two identical hydrogen atoms. So those do not qualify. But these are chyal centers and we have to be able to recognize that they are chyal centers even if the substituents are not drawn with wedge or dash bonds. Sometimes we draw molecules in line notation and we flatten everything out. So we're not depicting the accurate stereochemistry.

[00:02:13]They should be on dash or wedge bonds.

[00:02:15]But sometimes we forgo that for one reason or another. But we do need to still be able to recognize where those chyro centers are. So that is these four depicted in red. That's going to be C4 chyro centers.