[pfnm]

is (2R,3R)-dimethyloxirane a meso compound?

I know (2S,3S) is, because it contains a clear plane of symmetry.

(2R,3R) appears to contain a plane of symmetry. If I look at the molecule from the top (staring down at the oxygen), it would look like I've depicted it (I think)....then if I rotate 180 degrees, I get the same molecule.



I used green and red to show where the methyl groups end up in a 180 degree rotation.

But once rotated 180 degrees it's superimposable, ie its the same molecule.

So both (2R,3S)-2,3-dimethyloxirane, and (2R,3R)-2,3-dimethyloxirane are meso compounds?

Is that correct? Or have I made an error?

Cheers

[sjb]

is (2R,3R)-dimethyloxirane a meso compound?

I know (2S,3S) is, because it contains a clear plane of symmetry.

(2R,3R) appears to contain a plane of symmetry. If I look at the molecule from the top (staring down at the oxygen), it would look like I've depicted it (I think)....then if I rotate 180 degrees, I get the same molecule.



I used green and red to show where the methyl groups end up in a 180 degree rotation.

But once rotated 180 degrees it's superimposable, ie its the same molecule.

So both (2R,3S)-2,3-dimethyloxirane, and (2R,3R)-2,3-dimethyloxirane are meso compounds?

Is that correct? Or have I made an error?

Cheers

The symmetry in (2R,3R)-2,3-dimethyloxirane is an axis, not a plane; so this (and (2S, 3S) ) are not meso. But (2R,3S) is.