MC6: Which of the following Fischer projections represent a...

MC6: Which of the following Fischer projections represent a pair of enantiomers? CH3 Br-H H-Cl CH2CH3 I CH3 H-Cl Br-H CH2CH3 II CH2CH3 Cl-H Br-H CH3 III CH3 Br-H Cl-H CH2CH3 IV a. I and II b. III and IV c. I and IV d. II and III e. None

Labs

Want to see this concept in action?

NEW

Explore this concept interactively to see how it behaves as you change inputs.

View Labs

Transcript

00:01 In this problem, you're getting four fisher projections, and you're asked which of these are anantumurs.

00:07 So, first of all, remember, anantumers are going to have opposite stereocentors, so if one has r, the other is s.

00:14 Here we have two stereocentors, so we're looking at, if we had rs for one, we have sr for the other.

00:23 So we're just going to keep reversing it, and they should be opposites.

00:27 So if we look here, notice that in our top two, bromine and chlorine are on different sides, whereas down here, they're on the same side.

00:38 So right away, we can determine that one and two are going to be different than three and four.

00:51 So we can just compare now one and two to each other and three and four to each other.

00:58 And if we start with one and two, bromine has top priority.

01:04 This carbon has a chlorine, so it would be second priority.

01:08 This will be third.

01:11 Here, we go in counterclockwise direction, so you think s.

01:16 But hydrogen is in front of the plane.

01:19 So this gives us r.

01:22 If we check over here, because this is going to be the same carbon as this, we're going to have our priorities again.

01:37 But here, notice that the carbon attached to our ethyl group has bermine instead of chlorine...

Question

MC6: Which of the following Fischer projections represent a pair of enantiomers? CH3 Br-H H-Cl CH2CH3 I CH3 H-Cl Br-H CH2CH3 II CH2CH3 Cl-H Br-H CH3 III CH3 Br-H Cl-H CH2CH3 IV a. I and II b. III and IV c. I and IV d. II and III e. None

Please give Ace some feedback