Indicate whether each of the following structures is (R

Question

Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane:

e. Structural representation of 2-chlorobutane showing its chirality with labeled groups for R and S configuration analysis.

f. Structural representation of 2-chlorobutane showing hydrogen and chlorine atoms for R and S configuration analysis.

Accepted Answer

Hey everyone and welcome back, identify R three bromo hexane and S3 bromo hexane from the structures shown below. And the two structures that we are given, they are three bromo hexane stereo isomers in particular, they are two in anti and they are given in their new projections. So let's start with a, we have to consider the engle pre rules and we notice that the front carbon is chiral. It has four different substitutions. We're going to assign our priorities to each of our four substitutions and we are going to give Bromine priority number one because the other substitutions are hydrogen, carbon and carbon in the back. So Bromine has the greatest atomic number and it gets priority number one. Hydrogen gets priority # four because it has the lowest atomic number now because hydrogen is not in the back is priority number four. According to the angle log rules must be in the back, we cannot assign our rotation directly. And it basically means that we are going to redraw our structure in a bond life structure to correctly assign our configuration in an accurate manner. So we're going to read through our six member chain because we have three promo hack, that'd be 123456. And at position three, we are going to add, bro. Now, we have to understand that the perspective that we are seeing is Looking at our compound along our C3 C four bond. So we can draw an I going along our C3 C bond. Bromine is on a solid line. Our group is pointing a way in the structure that we have drawn. So we are going to add it on a dash and we are going to state E C for an L group. The reason why it's pointing away is simply because with respect to our eye, we're seeing it on the right side. So when we change the perspective and if we rotate our compound, the ethyl group will be pointing away from us while hydrogen is on the left of our, of our eye. So it will be pointing up on a watch while the group will be on a dash. And now when we consider our atoms for the back carbon carbon number four, it has two hydrogen atoms pointing up and then, and ethyl group pointing down. So we are also going to redraw it Such that two hygiene atoms are pointing on a wedge and on a dash, it doesn't really matter which one is which because they're equivalent. And then we have an L group on a solid line ride because it is basically parallel to bromine. So we are going to draw and a group. OK. And now that we see it, we can basically assign our priorities. Once again, we said for carbon number three, which is our chiral position, we have Bromine, then we have high priority number four, romi priority number one. And then we have a comparison between an ethyl substituent And a proposition because we have CH two CH 2 CH three. So a longer chain, which is a stray chain gets a higher priority versus a shorter chain, meaning a propal sub gets priority two and L subs gets priority three. Now we are going to assign our rotation. And if we trace our path from 1 to 2-3, that's what corresponds to a counterclockwise rotation. But hydrogen priority four is pointing up or basically pointing towards the viewer. So we need to reverse our assignment, meaning even though it's going counterclockwise, which would correspond to an s rotation in actuality, that's R due to the fact that we need to reverse it whenever priority number four is not pointing down right or basically away from the viewer because it's pointing towards the viewer, we are reversing our assignment to our meaning. The first structure is R. And now that means the second structure must be s because we have a comparison between R and S in anti. But let's verify that. Why don't we redraw that structure? So when we consider our chiral carbon atom, we control hydrogen pointing up. Now, what we are seeing is just Bromine on the left side. And that means when we look at it from the perspective, Bromine will be pointing up towards the viewer, when we essentially rotate our structure with respect to the vertical line, so that we can actually see our C C bond, bro will be pointing up, then the S L group will be pointing away from the V R down on a dash. So we can draw our E A group and then we will have our propal group on the left, right. So we are just going to add it on a solid line and state that we have a prop group, we can also fix our bond angles a bit to make it look neater. Of course, that's not really important to assign our configuration, but for complete clarity. So now that we got our structure, we remember that priorities were one for bro, four for hygiene, T for propo because it's longer than And then three for SL. Now hydrogen must be pointing away from the viewer. So we, we can essentially change our perspective and actually, we can look along our carbon hydrogen bond and we will essentially see bromine on the left, we will see our purple group and on the right, we will see our E group. So Bross priority one prop priority two and S L S priority three. When we assign our rotation, we get 1-3, that's our counterclockwise rotation, which is us. And this is the actual rotation because we changed our perspective, right? We looked at our structure that we have drawn and we understood that we have to change the perspective and look along our carbon hydrogen bond. So we definitely verify that B is S so we can conclude that A is R three bromo ha and then B is S three bromo hack. We have got our correct answers and we have labeled them in a green box and based on our answers, we can conclude our video. Thank you for watching and I hope to see you in the next one.

Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane:
e.
f.

Key Concepts

Chirality

Cahn-Ingold-Prelog Priority Rules

R and S Configurations

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