I can't seem to understand why these compounds are meso compounds..... I don't see any plane of symmetry here. I have trouble identifying meso compounds so can you give me heads up on how to identify them
Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. It only takes a minute to sign up.Sign up to join this community
Why don't use the definition just above the image?
A term for the achiral member(s) of a set of diastereoisomers which also includes one or more chiral members.
Achiral, i.e. the molecule is superimposable with its mirror image. So, if finding a plane of symmetry, or other symmetry elements in the molecule is difficult for you, a simpler method (and according to the definition) might be drawing a mirror image, i.e. all chiral elements inverted
or unchanged but drawn "right-to-left", i.e. flipped
or flipped vertically
.. (just use any of the mirroring methods) and deciding whether it's the same molecule (stereoisomer), by rotating it, in 3D, in your head. (Some internal rotations around single bonds might be needed as well.)
In the first case, the mirrored structure can be superimposed with the original one by in-plane 180° rotation around an axis perpendicular to the paper plane.
In the second case it can be done by 180° rotation around the in-plane horizontal axis.
In the third case it can be done by 180° rotation around the in-plane vertical axis.
Meso compounds need not only have a plane of symmetry. They can also have a point of symmetry.
The upper left compound has a point of symmetry at the centre of the central C-C bond.
The upper right compound has a plane of symmetry passing through the central H & OH groups.
The lower compound has a plane of symmetry passing through the common side of the two benzene rings.
The ideal way to identify the line of symmetry is to analyse the compound in 3-D. You may use models for that.