Chirality

[StarlingForce1]

Isn't there some trick for chirality problems that you don't need to reorient the molecule? Like if you just skip over the lowest priority substituent when following the circle (CCW or CW) don't you just assign the opposite value to what that method would yield? Like if you skip over a hydrogen when following the order of substituents on the carbon and you get an R configuration, you just assign it S instead?

Also, if I have two carbons attached to the chiral center, and one of those carbons is a carbonyl, but the other carbon has a hydroxyl group, I assign the carbonyl the higher priority because it is as if it is attached to two oxygens, right?

If someone could please provide some clarification it would be very much appreciated!

---

Members don't see this ad.

 

[sc4s2cg]

1. There are multiple tricks you can use, including some with your hand. The one that I think you are talking about is where you switch the lowest priority group with the group that is in the back. Then you do your thing, find that the molecule is R and assign it S instead:

So in this molecule, you would switch F with Cl (F is lower mw). Then assign priorities, determine the config, and assign the opposite.

2. Yes, you are right. A double bond or triple bond to a molecule means there are two or three connections, so 3 carbons or 2 carbons for example.