Carbohydrate Sterochemistry (5/13)

Isomers that differ in the spatial arrangement of their atoms around a stereocenter

a carbon with 4 different substituents attached

asymmetrical and non-superimposable mirror image EX) hands

Specific non-superimposable mirror images

Are superimposable with their mirror image They either lack a chiral center or are meso compounds

Contain multiple chiral centers that create a plane of symmetry within the molecule

Differ at one chiral carbon

d/+= rotates light to the right l/-= rotates light to the left

One or two stereocenters and is based off of the Cahn-Ingold-Prelog Priority Rules

1) identify stereocenters 2) assign priority to side groups (higher atomic number, then mass, then # of bonds) 3) lowest priority group should point away 4) assign R/S

Based on fisher projection of glyceraldehyde D= when OH on stereocenter points right L= when OH on stereocarbon points left

Go off of the furthest from the carbonyl we use

Stereoisomers that are not superimposable mirror images of each other

L-glucose and D-glucose

D-glucose and D-talose because they do not differ at all chiral centers

Special typer of diastereomers that only differ at one chiral center

carbonyl carbon when open chain is anomeric carbon. When cyclized, the hydroxyl group on the anomeric carbon may either point up or down. down= alpha, up=beta

Different conformations can be achieved without breaking any bonds