1. Chirality “chiral” Greek for hands chiral =
non-superimposable mirror images
chiral =
no plane of symmetry C*
C with 4 different substituents
stereocenter
chiral C

2. Chirality H H HOH2C C CHO OHC C CH2OH OH OH enantiomers*
CHO
OHC C
CH2OH OH OH
enantiomers
non-superimposable mirror images
no plane of symmetry

3. 3-D Representations O C H H OH C C H HOH2C CHO OH glyceraldehyde*
2,3-dihydroxy
propanal
CHO
vertical = into paper * H OH
horizontal = out of paper
CH2OH

4. (+)-glyceraldehyde (-)-glyceraldehyde * * CHO OH H CH2OH CHO HO H

5. Enantiomers identical in most properties differ in:
1.interaction with polarized light
2. interaction with chiral environments
Light interacts with molecules
when it passes through them
[interaction of electrical fields]
When light encounters mirror image
of molecule, interaction is reversed

6. Polarized light One enantiomer - rotate light to the left (-)
Other enantiomer -
rotate light to the right
(+)
in 50/50 mix -
no net rotation
racemic mixture
one enantiomer -
polarized light will be rotated
optical activity

7. Chirality 2. Enantiomers in chiral environments hands chiral mittens
achiral -
plane of symmetry
achiral environments
don’t distinguish between enantiomers
gloves
chiral -
no plane of symmetry
chiral environments
do distinguish between enantiomers

8. Chirality caraway seed enantiomers of carvone spearmint gum
Is there a C* *
Is there a plane of symmetry no
carvone

9. Chirality (-) carvone (+) carvone spearmint caraway
H3C
CH2 *
CH3 O C
H2C *
(-) carvone
(+) carvone
spearmint
caraway
rotates light to left
rotates light to right
racemic mixture - optically inactive
taste buds are chiral environment

10. Formation of chiral compounds
catalyzed by chiral enzymes
alkene + H2O
alcohol
fumerase
chiral *
+ H2O
fumaric acid
optically inactive
COOH * HO H
(+)
Malic acid
CH2CO2H
optically active

11. carboxylic acid + alcohol ester + H2O
O-CH3 * + *
CH3OH
+ H2O
(-)
lactic acid
(+)
methyl
lactate
optically active
optically active

12. ketone mild reducing agent 2o alcohol + + pyruvic acid (-) lactic acid
NaBH4 * HO * H H OH
pyruvic acid
(-) lactic acid
(+) lactic acid
optically inactive
optically active
optically active
racemic mixture
inactive

13. Compounds with more than 1 C*
CHO
CHO
CH2OH HO H * H OH * H OH
CH2OH
L-Erythrose
D-Erythrose

14. 2 C* A maximum of 2n steroisomers enantiomers diastereomers
CHO
CH2OH OH H
D-Erythrose HO
CHO
CH2OH H
L-Erythrose
A maximum of
2n steroisomers * * * *
enantiomers
diastereomers
CHO
CH2OH OH H HO
CHO HO H
enantiomers H OH
diastereomers:
non-mirror image
stereoisomers
CH2OH
L-Threose
D-Threose

15. 22 = 4 stereoisomers only 3 steroisomers I II III IV plane of symmetry| C H OH * *
+ LiAlH4 I II
CH2OH * OH HO
CH2OH
III IV
CH2OH * OH
CH2OH * HO * OH * HO
CH2OH
plane of symmetry
I and II
enantiomers
III and IV
meso compound
optically active
optically inactive