Assign R or S configuration to each chirality center in the following molecules: (a) (b) (c)

Name: Problem 44, Chapter 5: Organic Chemistry
Uploaded: 2023-07-01T19:53:56-08:00
Duration: 14 min 27 s
Channel: Mathew Botros
Description: Assign R or S configuration to each chirality center in the following molecules: (a) (b) (c)

step 1 Okay, hello everyone. We're going to be doing an organic chemistry problem from the textbook of

Assign R or S configuration to each chirality center in the...

Key Concepts

Chirality Center

A chirality center, often a carbon atom bonded to four different substituents, creates a non-superimposable mirror image of the molecule. This property is fundamental in stereochemistry, as the specific spatial arrangement of the substituents determines the molecule’s optical activity and biological interactions.

Cahn-Ingold-Prelog Priority Rules

These are a set of guidelines used to rank the substituents attached to a chirality center based on atomic number, atomic mass (when necessary), and connectivity. The rules enable the unambiguous assignment of priorities, which is essential for determining the absolute configuration (R or S) of the stereocenter.

Absolute Configuration (R/S) Assignment

This concept involves assigning a configuration to a chirality center by orienting the molecule so that the substituent with the lowest priority is directed away from the observer. The order of the remaining substituents is then analyzed, where a clockwise sequence indicates an R (rectus) configuration and a counterclockwise sequence indicates an S (sinister) configuration. This method ensures a consistent description of the molecule's three-dimensional structure.

Transcript

00:02 Okay, hello everyone.

00:04 We're going to be doing an organic chemistry problem from the textbook of the ninth edition written by john mcmurray and we're going to be doing another assigning r or s configuration to each chirality centers.

00:25 So let's draw out the first molecule and then we'll move on.

00:30 So it basically just looks something akin to this, has a wedge.

00:42 I'm going to color it in and make sure you do that on the exam or homework.

00:59 So we basically have a, let me fix that.

01:06 We basically have something akin to a methyl group.

01:16 Let me erase that little.

01:23 So one, two, three, four.

01:26 This is a butane, butane, sorry.

01:30 It's alpane, not alkene.

01:34 Let us have this.

01:44 Yeah.

01:44 Now the two compounds, two groups are oh.

01:50 Let me erase that as well as erase that here.

01:58 There is a h here.

02:02 This side is an oh.

02:04 It's not perfect.

02:08 Just make sure everything, this line right here has to be very straight.

02:11 We have a wedge, we have a dash.

02:14 This is in the back.

02:14 This is in the front.

02:16 So basically what we want to do is label the priorities and the hydrogen always has to be in the back.

02:25 So this is going to be four.

02:30 This is going to be one.

02:37 Now you have to figure out you have two and three.

02:40 Basically i would make this two, this area here, two, this area here, three.

02:54 So technically it technically could actually, yeah, i let you make sure you always don't make this mistake.

03:29 Let me draw the, i believe this should be two.

03:38 This should be three.

03:51 And you're going to see why, because if i rotate it in a clockwise position, this oh is in the back and the hydrogen is in the front.

04:07 But if i were to put this in the back and this in the front, this, it would go in the other direction.

04:18 So the configuration for this one, it looks r, it's actually s.

04:35 So if you have it, if you label it the other way, the one, two, three, you could still make it s, but you got to be careful with that because by that logic, then your answer would have been, it will look s, but it's actually r.

04:53 So you got to be very, you got to be very careful with that.

05:02 You got to be very careful when you're doing these kinds of problems.

05:06 The next one has a benzene ring, but we're going to try to look at, we're going to try to look at the chirality center with a chlorine this time.

05:27 We, for this first one right here, i believe that one, you could also just make this a three and then this a two so that it actually goes more with the r.

05:49 You could do this as also as a three, but it would still turn out the same exact answer.

05:59 So if you want to like another reason, it's because it depends on where you put the priorities, which one would matter more.

06:06 So i think this would be a way better answer than what was previously.

06:09 But moving on to the next one.

06:13 So we have benzene ring, and now i do apologize for making this video longer based on the drawing, but you got to make it accurate.

07:04 Then we have a butane group up here.

07:09 We have a wedge.

07:17 Let me just color that in.

07:25 Let me just really make it look more like a wedge.

07:39 Let me fix it.

08:00 This is a cl, chlorine, and the other side is a dash, dashes.

08:21 And that one is h...