For the compound 1-ethyl-3-isopropylcyclopentane,

Question

Structural representation of 1-ethyl-3-isopropylcyclopentane showing cis and trans isomers.

(d) LOOKING AHEAD What is the relationship between a cis isomer and a trans isomer?

Accepted Answer

Welcome back everyone. The figure below shows a ce and a trans iser for a compound one metal, two isopropyl Beane. We're given their structures and we want to identify the relationship between AC eer and A trans iser. There are four answer choices. A, they are identical B constitutional isomers C in anti and D. They ask the Immers before we consider this problem, we have to check two conditions. The first one is chirality. Let's see if the two carbon atoms that are represented by dashes and wedges are Kral specifically if we enumerate them. Number one is our metal group for the first compound number two for the isopropyl group. And then if we choose another color and label carbons, number one and two, for the carbons having a methyl group and an isopropyl group respectively, we want to check if they have four different substitutions and actually both of them have four different substitutions. So they are both chiral, for example, carbon number one has a methyl substituent and implicit hydrogen atom. And then if we go along the rank, we will have to, compared to the counterclockwise direction where we have C H and an isopropyl group bonded to the same carbon atom. So we have our difference going clockwise and counterclockwise. So that gives us two additional different substi meaning all the substations are different, we will observe the same thing for carbon number two. So they're both chiral number two, we want to check for any presence of an internal line of symmetry. And if we think about a horizontal line passing through the four membered ring, we will notice that the two parts of the compound are not the same. So there's no internal line of symmetry, that's really good for us because we understand that the dashes and wedges really have a meaning both carbon atoms are chiral and they or these two structures cannot be superimposed immediately well done. So we understand that the two structures cannot be identical. So we are going to get rid of option A that's because we have satisfied both of our conditions. The two compounds are not meso because there's no internal line of symmetry and chirality is present. So even though they have the same name, they are not identical due to the presence of stereoisomerism, since we satisfied both of our conditions. Now constitutional, we are going to get rid of that as well. Constitutional isomers will have a different name. And now in this case, we have exactly the same name applicable to each structure. Constitutional isomers must have the same molecular formula, but a different linkage of the substitutions. But our substitutions are on the same carbon atoms. Now, in an tumors, in order to think if they are in an, we have to remember that in animorphs are non superimposable mirror images of each other. So let's go ahead and draw the first structure. And now what we want to do, we want to imagine a mirror plane. And if we want to draw the mirror image of that structure, we are just going to flip it with respect to a vertical line or rotate at 180 degrees. But instead of doing that, we're just going to think about the trans isomer. And instead we're going to rotate the trans isomer to see if they are mirror images. And if we are rotated, we will notice that our dashed bond will become a wedged bond. So we will have a wedge for the muscle group and our wedge for the isopropyl group will become a dash. We noticed that they are not mirror images of each other due to the fact that the metal group is pointing down and up respectively. So they cannot be in an tumors, meaning they must be they asked to immerse which makes sense, right? Because the ers are defined as stereo isomers that are not in an they have chiral centers, the two structures are also chiral. But when we consider the mirror plane, they are not mirror images of each other. On the other hand, if we consider the dashes and wedges. It can be even easier for us to understand that without visualizing the mirror plane, let's say we consider the first structure and we understand that we have two bonds on dashes. That means both of them are pointing down relative to the screen. For the second structure, we have a wedge for carbon number two and a dash for carbon. Number one, they in anti will always have opposite configurations for corresponding carbon atoms. So carbon number one has exactly the same configuration because the metal group is winding down. But carbon number two has a flipped configuration. So if we're only partial, if flipping our configurations such that we're keeping a configuration of at least one carbon atom fixed while flipping the others, we will get get the astro. So an example of an anti in this case would be carbon number one pointing down on a dash. Carbon number two pointing down on a dash. So it's inaner will be a structure which will have both of the bonds pointing up because we have to flip both of them. So that will be in but the as the will have at least one of the coral carbon atoms pointing in the same direction. So in this case, we have structure number one with down for copper, number one and down for copper number two, for the trans isomer, the first carbon has a bond pointing down in the second one pointing up. So even though we are flipping the configuration of the second carbon, we keep the first one fixed exactly the same in each case, which gives us the, and that is our final answer. So the correct answer to this multiple choice question is D, the S and trans isomers are the, the. Thank you for watching.

For the compound 1-ethyl-3-isopropylcyclopentane,

(d) LOOKING AHEAD What is the relationship between a cis isomer and a trans isomer?

Key Concepts

Cis-Trans Isomerism

Steric Hindrance

Physical Properties of Isomers

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