Carbohydrate Sterochemistry (5/13) Flashcards
Stereoisomer
Isomers that differ in the spatial arrangement of their atoms around a stereocenter
Stereocenter/chiral center
a carbon with 4 different substituents attached
A molecule with a single chiral center
asymmetrical and non-superimposable mirror image
EX) hands
Enantiomers
Specific non-superimposable mirror images
Achiral molecules
Are superimposable with their mirror image
They either lack a chiral center or are meso compounds
Meso compounds
Contain multiple chiral centers that create a plane of symmetry within the molecule
Diaseteromers
Differ at one chiral carbon
d/l or +/- system
d/+= rotates light to the right l/-= rotates light to the left
R/S system
One or two stereocenters and is based off of the Cahn-Ingold-Prelog Priority Rules
Rules of R/S system
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
D/L system
Based on fisher projection of glyceraldehyde
D= when OH on stereocenter points right
L= when OH on stereocarbon points left
What to do when more than one stereocenter in a molecule and using the D/L system
Go off of the furthest from the carbonyl we use
Enantiomers
Stereoisomers that are not superimposable mirror images of each other
Example of enantiomers
L-glucose and D-glucose
Examples of Diastereomers
D-glucose and D-talose because they do not differ at all chiral centers
