Topic 3: Stereoisomers and Chirality pt 3

Question 1

Enantiomers and Same Molecules based on RS Confgurations

Answer 1

Two otherwise identical molecules have opposite R & S. = Enantiomers

Same R & S configuration= Same Molecule

Question 2

Physical Properties of Enantiomers

Answer 2

Enantiomers: Different compounds but have the same melting point, Boiling Point, and Density.

Rotate the plane of polarized light in the same magnitude, but in opposite directions

Question 3

Polarized Light

Answer 3

Waves vibrate one plane

Question 4

Optical Activity

Answer 4

Enantiomers rotate in opposite directions but at the same degree.

Question 5

Polarimeter

Answer 5

Chiral molecules rotate plane-polarized light-> optically active.

> Rotate plane polarized light clockwise are Dextrorotatory (+)

> Rotate plane-polarized light counterclockwise are Levorotatory (-)

Question 6

Optical Rotation and Absolute Configuration

Answer 6

No relationship between the R & S configuration of an enantiomer… depends on direction it rotates polarized light (Must be determined by experiment)

Question 7

Polarimeter

Answer 7

specific rotation= alpha a = (observed rotation a)/(length, dm)(concentrate ion)

Question 8

Optical Purity

Answer 8

Optical Purity= (Observed specific rotation) / (specific rotation of the pure enantiomer) x100%

Question 9

Racemic Mixtures

Answer 9

Equal amounts of 2 enantiomers.

**Important
>d- and l-enantioemrs
>notation (del) or (+-)
> No optical activity
>May have a different boiling point (b.p.) and melting point (m.p.) from enetiomers.

Question 10

Chirality of Conformational Isomers

Answer 10

The 2-chair conformations of cis-1,2-dibromo cyclohexane is superimposable.
** Interconversion is fast… racemic… optically inactive (50/50 amount)

Question 11

Extra Notes from Video

Answer 11

S enantiomers-> (+) Right Dex

R enantiomers -> (-) Left Lev