Stereochemistry Source http biochemistry utoronto casteipe Childish Fantasy

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.

Enantiomers Stereoisomers that are nonsuperposable mirror images of each other.

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 • Diastereomers – Nonsuperposable – Not Mirror Images – Differ in physical properties • Enantiomers – Nonsuperposable – 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 • 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

Anomers

Glycosidic Bonds

Polysaccharides • Glycogen – 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

Structural Relationships NO Yes Same MF Different NO Same Connectivity NO Yes Superposable Yes Structural Isomers Mirror Image & Stereocenter Mirror Image NO Diastereomers Yes Enantiomers NO Yes Identical Meso

Problems (p. 235) • • 5. 39 5. 40 5. 43 5. 52