Which of the following is not a meso compound

Will post question in a bit

Question

Which of the following is not a meso compound

Will post question in a bit

photon336 · Answer

choices B,C,D

photon336 · Answer

Choices A, B Sorry this got cut out

photon336 · Answer

What I did was in switched he configurations of all the chiral centers and then saw if the molecules were super imposable. 
Eliminated B,C, A

Thought it was D

Was wrong.

empty · Answer

Ohhhhh the question is asking which is NOT meso.

All of these are meso except for one. In order to be meso it just means it has a plane of reflection.

So if we look at D we can see that putting a plane of reflection through the center will cause it to reflect onto itself, so it's meso.

photon336 · Answer

i suck at drawing that stuff out .. it's hard to visualize.. I think I need to see how this is down.. it says the answer is A but I can't see why. I mean to be meso a compound has to have at least 2 chiral centers and a plane of symmetry.

empty · Answer

Do you have a model kit or some way you can build these? That might help I think. If you reverse the first one you'll have these two: |dw:1437254359528:dw| It might appear at first glance that this is meso, however there's actually no way to superpose one on the other! Try flipping either one around 180 degrees and they stay the same, like this: |dw:1437254464648:dw| So the OH group on the front right will rotate around to be the back left group after rotating, so it becomes itself by rotating. This might be confusing, but this means that reflection literally turns this molecule into a different thing that no matter how much you rotate it, it will stay the same and NOT look like the original one it was reflected from. I think it'll take some practice, this MIGHT help but I don't know if it will help specifically for anything, it's meant for finding symmetry groups of molecules in an advanced inorganic chemistry course. At the very least it might be fun to play around with. http://symmetry.otterbein.edu/gallery/index.html Don't take the bonds too literally here, it's pretty cartoony here, so don't worry too much about molecular orbitals while looking at the models on this site.