Stereochemistry Source: http://biochemistry.utoronto.ca/steipe/
Childish Fantasy “Not long ago, I expressed the view that the lack of general education and of thorough training in chemistry was one of the causes of the deterioration of chemistry research in Germany …. Will anyone to whom my worries seem exaggerated please read, if he can, a recent memoir by a Herr Van’t Hoff on “The arrangement of Atoms in Space”, a document crammed to the hilt by the outpourings of a childish fantasy…..” Written by Hermann Kolbe in 1877 Source: Solomons Organic Chemistry chapter 5
Significants (R)-limonene smells of oranges while its enantiomer (S)-limonene smells of lemons Source: http://nobelprize.org/chemistry/laureates/2001/public.html
Constitutional Isomers Same Molecular Formula but different Structural Formula. (Different Connectivity)
Diastereomers Stereoisomers that are not mirror images of each other. Cis/Trans isomers are a type of diastereomer.
Diastereomers Stereoisomers that are not mirror images of each other. Cis/Trans isomers are a type of diastereomer.
Enantiomers Stereoisomers that are nonsuperposable mirror images of each other.
Enantiomers Enantiomers occur with chiral molecules. Chiral from the Greek cheir meaning “Hand”.
Chiral Enantiomers occur with chiral molecules. Chiral from the Greek cheir meaning “Hand”.
Diastereomers vs. Enantiomers Nonsuperposable Not Mirror Images Differ in physical properties Enantiomers Mirror Images Same physical properties
Existence Interaction with Enzymes and Receptor Sites Stereospecific Stereoselective Rotation of Light Dextrorotatory (Clockwise rotation) Levorotatory (Counterclockwise rotation) Louis Pasteur Visual Separated with tweezers
Nomenclature Systems +/- (Rotation of Light) Right Handed / Left Handed Helix (Hand) +/- (Rotation of Light) D/L (Base Molecule ) R/S (Periodic Table) Anomers (Functional Group Location)
Right Handed / Left Handed Helix Right Hand Rule Left Hand Rule
+/- System
D/L System
D/L System
D/L System
Anomers
Glycosidic Bonds
Glycosidic Bonds
Polysaccharides Glycogen Starch (amylose or amylopectin) Storage form of glucose in Animals Branches every 6 to 10 glucose residues Starch (amylose or amylopectin) Storage form of glucose in plants Branches every 20 glucose residues Cellulose (Fiber) Structural component of plant cell walls Contains β-1,4-glycosidic bonds
R/S System First assign priority based on Periodic Table Second rotate lowest priority to the back
R/S System Third connect three highest priorities in order
R/S System If clockwise assign R for Rectus If counterclockwise assign S for Sinister
R/S System Assign R and S designations to the structures
R/S System
R/S System Assign R and S designations to each stereocenter
Meso
Meso
Meso
Structural Relationships Same MF NO Yes Same Connectivity Different NO Yes Superposable NO Yes Structural Isomers Mirror Image & Stereocenter Mirror Image NO Yes Yes NO Diastereomers Enantiomers Identical Meso
Problems (p. 235) 5.39 5.40 5.43 5.52