Stereochemistry

Constitutional Isomers

molecules that have the same molecular formula but differ in how their atoms are connected

distinct physical and chemical properties

Conformational isomers

same molecule different rotation

stereoisomers

same atoms, same connectivity but different bond direction or 3d shape
cannot interconvert by conformational change

Chiral

a molecule that is not superimposable on its mirror image and has no plane of symmetry

Achiral

molecule with a plane of symmetry

Enantiomers

A pair of molecules where all wedges and dashes flip (stereocenters flip)

Diasteromers

stereoisomers that are not mirror images. Have distinct physical and chemical properties.
Not all wedges and dashes flip

Meso

a molecule that is achiral and superimposable on its mirror
molecule will have at least 2 stereocenters and be achiral

one side S and the other side as R

What if non of the stereocenters change?

Then the molecules are the same

what if there is a plane of symmetry

then there are no stereocenters

What if a backbone changes direction

then there is a change on the stereocenter attached to it.