Chapter 3 Stereoisomers & Chirality pt 2

Question 1

Drawing Enantiomers

Answer 1

Enantiomers: Are mirror objects of each other but different, not superimposable.

Diastereomers: These are not mirror objects of one another.

Question 2

Drawing Enantiomers: Perspective Formula

Answer 2

We use wedges(up) or dashes(down) to draw stereo centers.

Question 3

Drawing Enantiomers: Fisher Projections

Answer 3

Flat-line ways of drawing molecules that have one or more stereo centers.

*Still depicting 3D Stereochemistry, you must understand..
*Horizontal bonds are coming toward us
*Vertical bonds are going away from us.

Question 4

Converting Wedge and Dash (perspective) lines to Fisher Projections

Answer 4

A=Wedge Line (H)
B=Dash Line(V)
C=Regular Lines (H)
D=Regular Line (D)

Question 5

Naming Enantiomers: The R, S System of Nomenclature on Perspective Formulas

Answer 5

Step 1: Look for the chiral center atom.

Step 2: Prioritize the four substituents coming off chiral center atoms.

Prioritize the atoms:
a.highest priority = highest atomic number I>Br>Cl>S>F>O>N
b.If a tie you go out one bond at a time until the tie is broken
c.Isotope atoms.. w/ the same atomic atomic number higher atomic weight.. 13C>12C>2H>1H

Question 6

(R)and (S) Configuration: Multiple Bonds

Answer 6

d.Treat double and triple bonds a bond to a separate atom

Question 7

Naming Enantiomers: The R,S System of Nomenclature on Perspective Formulas

Answer 7

Step 3: Number your substitute 1-4. (1=Highest priority 2,3, 4=lowest priority

Step 3: Point the lowest priority 3-D away from you.

Step 4: Make a circle from substituents 1 to 2 to 3 and finally 4.

**a.clockwise=R
b.Counterclockwise=S

***When rotating the lowest priority group to the back, keep one group in place and rotate the other 3.

Question 8

Naming Enantiomers: The R,S System of Nomenclature on Fisher Projections

Answer 8

A similar set of rules exists for use with Fischer Projections.

1. Group of lowest priority on the vertical line. Curve from group of highest priority to the group of second highest priority. (Clockwise=R)(Counterclockwise=S)

Question 9

Naming Enantiomers: The R,S System of Nomenclature on Fisher Projections (Pt2)

Answer 9

2.However if the the lowest priority is on horizontal line then follow step 1 but reverse R or S.

Rule of thumb: Lowest priority on VL then True, if Lowest priority is on HL then False

Question 10

Naming Enantiomers: The R,S System of Nomenclature on Fisher Projections (pt3)

Answer 10

Step 3: Curve highest priority to the group second highest priority.. its okay if you go past lowest priority but NEVER past third priority.