Isomers: Geometric and Diastereometric Isomers

[Stevo1925]

What is the difference between Diastereomers and Geometric Stereomers?

Im a little confused on this one as I thought they were the same thing?

Stevo1925

 

[Char. Limit]

I assume by Geometric Stereomers, you mean Geometric Isomers. Correct me if I'm wrong.

Geometric Isomers usually have the same atoms hooked to the other same atoms, but in a different way. Cis-2-Butene and Trans-2-Butene are examples.

Diastereomers have to do with chirality, and are currently hazy in my head right now, but I think that it's when a molecule has two chirality centers, You have (R,R), (R,S), (S,R), (S,S). (R,R) and (R,S) are diastereomers (as are (S,R) and (S,S)), while (R,R) and (S,S) are stereoisomers.

 

[Cesium]

Diastereomers have to do with chirality, and are currently hazy in my head right now, but I think that it's when a molecule has two chirality centers, You have (R,R), (R,S), (S,R), (S,S). (R,R) and (R,S) are diastereomers (as are (S,R) and (S,S)), while (R,R) and (S,S) are stereoisomers.

Diastereomers and enatiomers are both stereoisomers (isomers that have to do with chirality). Diastereomers are stereoiosmers that aren't enatiomers. Enatiomers are exact mirror images of one another- that is all chiral centers have opposite optical configurations. So in your example of two chiral centers RR and SS form one enatiomeric pair and SR and RS form another pair. Any other two pairs would be diastereomers (RR and SR, SS and RS). Note that diastereomers can also refer to molecules with greater than 2 chiral centers (eg. RSRR and RRRS). Enatiomers are identical except for the fact that they rotate plane polarized light in opposite directions. Diasteromers, on the other hand, have different chemical and physical properties (melting point, solubility, etc.)