In the conformations of the R,S shown above, the mirror plane should be obvious vertical plane bisecting the middle of the central C-C bond. R,S -2,3-dichlorobutane S,R -2,3-dichlorobutane. However, let's look at the other important conformation of the meso isomer and make sure we can recognise it is the meso isomer. The relationship of A to B is not immediately obvious. However, once the right hand end has been rotated about the central C-C bond by degrees, A can been seen to be the mirror image of B.
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And, they both have been singly substituted at each stereo-center. I also cannot find a plane of symmetry. How is 2A a meso compound? Further down the page I show how to do a rotation on the left-hand molecule so that you can clearly see the mirror plane.
Thanks for the info! I am a bit confused though because i thought number 2b was an enantiomer due to the r,s configuration being opposite in both. They are actually the same molecule, just rotated degrees. How to convert a Newman projections with two choral centres into a Fischer projection…..
You say that cis-1,2- dimethyl cyclohexane is meso. However, drawn as a chair, there is no plane of symmetry because one of the substituents is axial, the other equitorial. Am I understanding this correctly? Drawn as a chair, there is no plane of symmetry.
But it still is not a meso compound. The equilibrium mixture consists of interconverting enantiomers. That is why it is optically inactive, not because it is meso. You can fall into this trap with all 1,2-R,R-disubstituted even-numbered rings.
In the last figure, cis 1,2-dimethylcyclohexane does not seem to have a plane of symmetry when it is drawn in chair conformation. Can you please elaborate on this? Correct answer:. Explanation : This is the product of the given reaction. Example Question 85 : Stereochemistry. How many of the existing configurational stereoisomers are chiral? Possible Answers: 1. Correct answer: 2. Explanation : There are three configurational stereoisomers. Example Question 86 : Stereochemistry.
How many configurational stereoisomers exist for this structure? Possible Answers: 4. Correct answer: 3. Explanation : There are two tetrahedral asymmetrical stereocenters in this molecule the carbon atoms attached to each of the chlorine atoms.
Copyright Notice. View Organic Chemistry Tutors. Abhinav Certified Tutor. Donald Certified Tutor. Ethan Certified Tutor. Report an issue with this question If you've found an issue with this question, please let us know. Do not fill in this field. Louis, MO Or fill out the form below:. Company name. Copyright holder you represent if other than yourself. Doesn't matter how you do it. I'll rotate it again, and we can see we can't superimpose our atoms.
And we could check for a plane of symmetry, so I could take one of these and I can rotate it so we have our hydrogens going away from us in space. And I look for a plane of symmetry, but I don't see one. So this is not a meso compound. So one and two are enantiomers. They're non-superimposable mirror images of each other. And we could've guessed that because if we look at our chiral centers here, so this one has an OH coming out at us, and then that one has it going away from us, this one has an OH coming out at us and this one has it going away from us, so we have opposite configurations at both chirality centers.
Let's look at three and four next. So what is the relationship between these two? Well, first, we might think these could be enantiomers because at this carbon, we have OH on a wedge, and then here we have OH on a dash. And then here we have OH on a dash, and here we have it on a wedge. So that might be your first guess. But let's look at the video and let's look at the model sets to help us out.
Remember, I'm leaving the hydrogens off the methyl groups and the hydrogens off the oxygens in the video just to help us see the molecule more clearly. On the left, we have a model of drawing three. So here's our carbon chain with an OH going away from us in space, and an OH coming out at us in space. On the right is a model of drawing four. Here's our carbon chain with an OH coming out at us in space and an OH going away from us in space. So I'll hold the two models and we'll compare them.
First let's see if they are mirror images of each other. So I'll take the one on the right and I'll rotate it and I'll hold it up next to the one on the left. And now we can see that these two are mirror images of each other. So next, let's see if one is superimposable on the other. So I'll go back to the starting point and I'll rotate it around like that, and let's see if we can superimpose the one on the right, the mirror image, on the molecule on the left.
And notice that we can. All of the atoms line up. So all of the hydrogens, carbons and oxygens are in the same place. So this is a compound that has chirality centers, but it is achiral, the mirror image is superimposable on itself. So we should be able to find a plane of symmetry. So I'll just pick one of these models, doesn't matter which one because they represent the same compound, and I'll rotate, I'll rotate it around so we can see a plane of symmetry.
So right there is our plane of symmetry. So three and four actually represent the same compound. So this is one meso compound.
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