Created by Professor William Tam & Dr. Phillis Chang Chapter 5 Stereochemistry Chiral Molecules...

Created byProfessor William Tam & Dr. Phillis

ChangCopyright © 2014 by John Wiley & Sons, Inc. All rights reserved.

Chapter 5

StereochemistryChiral Molecules

© 2014 by John Wiley & Sons, Inc. All rights reserved.

About The Authors

These Powerpoint Lecture Slides were created and prepared by Professor William Tam and his wife Dr. Phillis Chang.

Professor William Tam received his B.Sc. at the University of Hong Kong in 1990 and his Ph.D. at the University of Toronto (Canada) in 1995. He was an NSERC postdoctoral fellow at the Imperial College (UK) and at Harvard University (USA). He joined the Department of Chemistry at the University of Guelph (Ontario, Canada) in 1998 and is currently a Full Professor and Associate Chair in the department. Professor Tam has received several awards in research and teaching, and according to Essential Science Indicators, he is currently ranked as the Top 1% most cited Chemists worldwide. He has published four books and over 80 scientific papers in top international journals such as J. Am. Chem. Soc., Angew. Chem., Org. Lett., and J. Org. Chem.

Dr. Phillis Chang received her B.Sc. at New York University (USA) in 1994, her M.Sc. and Ph.D. in 1997 and 2001 at the University of Guelph (Canada). She lives in Guelph with her husband, William, and their son, Matthew.


Table of Contents (hyperlinked)1. Chirality and Stereochemistry2. Isomerism: Constitutional Isomers and Stereoisomers3. Enantiomers and Chiral Molecules4. Molecules Having One Chirality Center Are Chiral5. More about the Biological Importance of Chirality6. How to Test for Chirality: Planes of Symmetry7. Naming Enantiomers: The R,S-System8. Properties of Enantiomers: Optical Activity9. The Origin of Optical Activity10. The Synthesis of Chiral Molecules11. Chiral Drugs12. Molecules with More than One Chirality Center13. Fischer Projection Formulas14. Stereoisomerism of Cyclic Compounds15. Relating Configurations through Reactions in Which

No Bonds to the Chirality Center Are Broken16. Separation of Enantiomers: Resolution17. Compounds with Chirality Centers Other than Carbon18. Chiral Molecules That Do Not Possess a Chirality Center


Table of Contents1. Chirality and Stereochemistry2. Isomerism: Constitutional Isomers and Stereoisomers3. Enantiomers and Chiral Molecules4. Molecules Having One Chirality Center Are Chiral5. More about the Biological Importance of Chirality6. How to Test for Chirality: Planes of Symmetry7. Naming Enantiomers: The R,S-System8. Properties of Enantiomers: Optical Activity9. The Origin of Optical Activity10. The Synthesis of Chiral Molecules11. Chiral Drugs12. Molecules with More than One Chirality Center13. Fischer Projection Formulas14. Stereoisomerism of Cyclic Compounds15. Relating Configurations through Reactions in Which No

Bonds to the Chirality Center Are Broken16. Separation of Enantiomers: Resolution17. Compounds with Chirality Centers Other than Carbon18. Chiral Molecules That Do Not Possess a Chirality Center


In this chapter we will consider:

How to identify, codify, and name the three-dimensional arrangement of atoms and molecules

How such arrangements can lead to unique properties and behaviors


1. Chirality & Stereochemistry

An object is achiral (not chiral) if the object and its mirror image are identical


A chiral object is one that cannot be superposed on its mirror image


1A.The Biological Significance ofChirality

Chiral molecules are molecules that cannot be superimposed onto their mirror images

Thalidomide

NNH

O

OO

O

● One enantiomer causes birth defects, the other cures morning sickness


● One enantiomer is a bronchodilator, the other inhibits platelet aggregation

NH

OMe

OMeOMe

HO

HO

Tretoquinol


66% of all drugs in development are chiral, 51% are being studied as a single enantiomer

Of the $475 billion in world-wide sales of formulated pharmaceutical products in 2008, $205 billion was attributable to single enantiomer drugs


2. Isomerisom: ConstitutionalIsomers & Stereoisomers

Isomers: different compounds that have the same molecular formula●Constitutional isomers:

isomers that have the same molecular formula but different connectivity –their atoms are connected in a different order

2A.Constitutional Isomers


Examples

andButane 2-Methylpropane

MolecularFormula

ClCl

and1-Chloropropane 2-Chloropropane

ConstitutionalIsomers

C4H10

C3H7Cl


Examples

MolecularFormula

and

Butanoic acid Methyl propanoate

OHOCH3

O

O

ConstitutionalIsomers

C2H6O

C4H8O2

OH CH3 O CH3andEthanol Methoxymethane


2B.Stereoisomers

Stereoisomers are NOT constitutional isomers

Stereoisomers have their atoms connected in the same sequence but they differ in the arrangement of their atoms in space. The consideration of such spatial aspects of molecular structure is called stereochemistry


2C. Enantiomers & Diastereomers Stereoisomers can be subdivided

into two general categories:enantiomers & diasteromers●Enantiomers – stereoisomers

whose molecules are nonsuperimposable mirror images of each other

●Diastereomers – stereoisomers whose molecules are not mirror images of each other


Geometrical isomers (cis & trans isomers) are:●Diastereomers

e.g.

(trans)Ph

PhPh Ph

(cis)and

Cl

H

Cl

H

H

Cl

Cl

H(trans)(cis)

and


Subdivision of Isomers

Isomers(different compounds with same molecular formula)

Constitutional Isomers

(isomers whose atoms have a different

connectivity)

Stereoisomers(isomers that have the same

connectivity but differ in spatial arrangement of their

atoms)

Enantiomers(stereoisomers that are

nonsuperimposable mirror

images of each other)

Diastereomers(stereoisomers that areNOT mirror images of

each other)


3. Enantiomers and Chiral Molecules

Enantiomers occur only with compounds whose molecules are chiral

A chiral molecule is one that is NOT superimposable on its mirror image

The relationship between a chiral molecule and its mirror image is one that is enantiomeric. A chiral molecule and its mirror image are said to be enantiomers of each other


OH(2-Butanol)

OHH

(I)

HO H

(II)

(I) and (II) arenonsuperimposa

blemirror images ofeach other


4. Molecules Having One ChiralityCenter Are Chiral

A chirality center is a tetrahedral carbon atom that is bonded to four different groups

A molecule that contains one chirality center is chiral and can exist as a pair of enantiomers


The presence of a single chirality center in a molecule guarantees that the molecule is chiral and that enantiomeric forms are possible

An important property of enantiomers with a single chirality center is that interchanging any two groups at the chirality center converts one enantiomer into the other


Any atom at which an interchange of groups produces a stereoisomer is called a stereogenic center (if the atom is a carbon atom it is usually called a stereogenic carbon)

If all of the tetrahedral atoms in a molecule have two or more groups attached that are the same, the molecule does not have a chirality center. The molecule is superimposable on its mirror image and is achiral


Me Et

ClH

(III)

CH

EtMeCl*

Me Et

HCl

mirror

MeEt

Cl H

(IV)

(III) and (IV) are nonsuperimposable mirror images of each other

Me Et

ClH

(III)

sameas


Me Me

ClH

(V)

CH

MeMeCl

Me Me

HCl

mirror

MeMe

Cl H

(VI)Me Me

ClH

(V)

sameas

(V) and (VI) are superimposable⇒ not enantiomers ⇒ achiral


4A.Tetrahedral vs. TrigonalStereogenic Centers

Chirality centers are tetrahedral stereogenic centers

Me Et

OHH

*(A)

mirror

MeEt

HO H

*(B)

Tetrahedral stereogenic center⇒ chiral

(A) & (B) areenantiomers


(C)H

Ph

Ph

H

mirror

(D)Ph

H

H

Ph

Trigonal stereogenic center⇒ achiral (C) & (D) are

identical

Cis and trans alkene isomers contain trigonal stereogenic centers


5. More about the BiologicalImportance of Chirality


The activity of drugs containing chirality centers can vary between enantiomers, sometimes with serious or even tragic consequences

For several years before 1963 thalidomide was used to alleviate the symptoms of morning sickness in pregnant women

Thalidomide


In 1963 it was discovered that thalidomide (sold as a mixture of both enantiomers) was the cause of horrible birth defects in many children born subsequent to the use of the drug

Thalidomide

NNH

O

OO

O

NNH

O

OO

O

enantiomer ofThalidomide

(causes birth defects)(cures morning sickness)


6. How to Test for Chirality:Planes of Symmetry

A molecule will not be chiral if it possesses a plane of symmetry

A plane of symmetry (mirror plane) is an imaginary plane that bisects a molecule such that the two halves of the molecule are mirror images of each other

All molecules with a plane of symmetry in their most symmetric conformation are achiral


Me Me

Cl

H

Me Et

Cl

H

Plane of symmetry

No plane of symmetry

achiral

chiral


7. Naming Enantiomers:The R,S -System

Using only the IUPAC naming that we have learned so far, these two enantiomers will have the same name:● 2-Butanol

This is undesirable because each compound must have its own distinct name

OHH

(I)

HO H

(II)

OHRecall:


Rule 1●Assign priorities to the four

different groups on the stereocenter from highest to lowest (priority bases on atomic number, the higher the atomic number, the higher the priority)

7A.How to Assign (R) and (S)Configurations


Rule 2●When a priority cannot be

assigned on the basis of the atomic number of the atoms that are directly attached to the chirality center, then the next set of atoms in the unassigned groups is examined. This process is continued until a decision can be made.


Rule 3●Visualize the molecule so that

the lowest priority group is directed away from you, then trace a path from highest to lowest priority. If the path is a clockwise motion, then the configuration at the asymmetric carbon is (R). If the path is a counter-clockwise motion, then the configuration is (S)


CH2

CH3C

O H

Step 2: CH3

Example HO H(2-Butanol)

①

③

④

② or ③ ② or ③CC

O HStep 1:

① ④

②

(H, H, H) (C, H, H)


OH

EtMe

①

④

②③

OH

EtMe

H

OH

EtMe EtMe

HO H

=

OH

EtMe

H

Arrows are clockwise

(R)-2-Butanol


OCH3

H3C CH2CH3Br

Other examples

①

④

②

③

Cl

H CH3HO

Cl

CH3HO

Counter-clockwise

(S)

①

④

②

③

OCH3

CH2CH3Br

Clockwise

(R)


Cl

H OHBr

Cl

Br HHO

Other examples

①

④

②

③

Cl

OHBr

Clockwise

(R)

● Rotate C–Cl bond such that H is pointed to the back


OCH3

H IH3C

H

I OCH3H3C

Other examples

①④

②

③

OCH3

IH3C

● Rotate C–CH3 bond such that H is pointed to the back

Counter-clockwise

(S)


Rule 4●For groups containing double or

triple bonds, assign priorities as if both atoms were duplicated or triplicatede.g. C O C

OOC

as

C C CC

CC

as

C C CC

CCC

asC


Example CH3

H CH=CH2HO①

④ ②

③

(S)

CH3 CH CH2

CH

CCC

HH

CH3

CH CH2

Compare & :

equivalent to

Thus, (H, H, H)

(C, C, H)CH CH2


Other examples

OH

HCl

CH3

O①

④

②

③

(R)

H2C

HCl

CH3

O

OH

①

④②

③

(S)

C (O, O, C)

C (O, H, H)

②

③


8. Properties of Enantiomers:Optical Activity

Enantiomers●Mirror images that are not

superimposable

mirror

H3CH2C

*

CH3

H

ClCH2CH3

*

H3C

H

Cl


Enantiomers have identical physical properties (e.g. melting point, boiling point, refractive index, solubility etc.)

Compound bp (oC) mp (oC)

(R)-2-Butanol 99.5

(S)-2-Butanol 99.5

(+)-(R,R)-Tartaric Acid

168 – 170

(–)-(S,S)-Tartaric Acid

168 – 170

(+/–)-Tartaric Acid 210 – 212


Enantiomers●Have the same chemical

properties (except reaction/interactions with chiral substances)

●Show different behavior only when they interact with other chiral substances

●Rotate plane-polarized light in opposite direction


Optical activity●The property possessed by

chiral substances of rotating the plane of polarization of plane-polarized light


The electric field (like the magnetic field) of light is oscillating in all possible planes

When this light passes through a polarizer (Polaroid lens), we get plane-polarized light (oscillating in only one plane)

Polaroidlens

8A.Plane-Polarized Light


A device for measuring the optical activity of a chiral compound

8B.The Polarimeter

a = observed optical rotation


8C. Specific Rotation

D[] =

25 c x

temperatureobserved rotation

wavelength of light(e.g. D-line of Na lamp,l=589.6 nm)

concentration of sample solutionin g/mL

length of cellin dm (1 dm = 10 cm)

ℓ


The value of a depends on the particular experiment (since there are different concentrations with each run) ●But specific rotation [a] should

be the same regardless of the concentration


Two enantiomers should have the same value of specific rotation, but the signs are opposite

mirror

HO

*

CH2CH3

CH3

H

[] = + 13.5o25

D

OH

*

H3CH2C

CH3

H

[] = 13.5o25

D


9. The Origin of Optical Activity






An equimolar mixture of two enantiomers is called a racemic mixture (or racemate or racemic form)

A racemic mixture causes no net rotation of plane-polarized light

9A.Racemic Forms

HC2H5

CH3

OH

(R)-2-Butanol

HC2H5

H3C

HO

(S)-2-Butanol(if present)

rotation

equal & opposite rotation by the enantiomer


A sample of an optically active substance that consists of a single enantiomer is said to be enantiomerically pure or to have an enantiomeric excess of 100%

9B.Racemic Forms and EnantiomericExcess


An enantiomerically pure sample of (S)-(+)-2-butanol shows a specific rotation of +13.52

D[] = +13.52

25

A sample of (S)-(+)-2-butanol that contains less than an equimolar amount of (R)-(–)-2-butanol will show a specific rotation that is less than 13.52 but greater than zero

Such a sample is said to have an enantiomeric excess less than 100%


Enantiomeric excess (ee) ●Also known as the optical

purity% enantiomeric

excess

moles of oneenantiomer

moles of otherenantiomer

total moles of both enantiomers

= x 100

% enantiomericexcess *

observed specific rotation

specific rotation of thepure enantiomers

= x 100

●Can be calculated from optical rotations


Example●A mixture of the 2-butanol

enantiomers showed a specific rotation of +6.76. The enantiomeric excess of the (S)-(+)-2-butanol is 50%

% enantiomericexcess *

+6.76+13.52

= x 100 = 50%


10.The Synthesis of Chiral Molecules

10A. Racemic Forms

O

CH3CH2CCH3 H H ( )-CH3CH2CHCH3

OH

+Ni

Butanone(achiral

molecules)

Hydrogen(achiral

molecules)

( )-2-Butanol(chiral

molecules; but50:50 mixture

(R) & (S))



10B. Stereoselective Syntheses Stereoselective reactions are

reactions that lead to a preferential formation of one stereoisomer over other stereoisomers that could possibly be formed● enantioselective – if a reaction

produces preferentially one enantiomer over its mirror image

● diastereoselective – if a reaction leads preferentially to one diastereomer over others that are possible


OEt

O

FOH

O

F

+ EtOHH+, H2O

heat

racemate ( ) racemate ( )

OEt

O

FOH

O

F

+ EtOH

H2Olipase

racemate ( ) ( )(> 69% ee)

OEt

O

F(+)

(> 99% ee)

+


11.Chiral Drugs

Of the $475 billion in world-wide sales of formulated pharmaceutical products in 2008, $205 billion was attributable to single enantiomer drugs

ONMe2

F

NC

Escitalpram(anti-depressant )

HO

HO

NH3

HCO2

L-DOPA(treatment for Parkinson's)


Singulair(asthma and allergy treatment)

Naproxen(anti-inflammatory drug)

MeO

CH3

CO2H

N

HOCH3

CH3S

NaO2C

Cl


12.Molecules with More than OneChirality Center

In compounds with n tetrahedral stereocenters, the maximum number of stereoisomers is 2n


12A. How to Draw Stereoisomers forMolecules Having More than OneChirality Center

Br

Br

2,3-Dibromopentane** 12

35

4


Start by drawing the portion of the carbon skeleton that contains the chirality centers in such a way that as many of the chirality centers are placed in the plane of the paper as possible, and as symmetrically as possible

C2C3


Next we add the remaining groups that are bonded at the chirality centers in such a way as to maximize the symmetry between the chirality centers

Br BrH H


To draw the enantiomer of the first stereoisomer, we simply draw its mirror image

Br BrH H

BrBrHH

mirror


To draw another stereoisomer, we interchange two groups at any one of the chirality centers• All of the possible stereoisomers for

a compound can be drawn by successively interchanging two groups at each chirality center

Br HH Br

BrHHBr

mirror


Next we examine the relationship between all of the possible pairings of formulas to determine which are pairs of enantiomers, which are diastereomers

Br BrH H

BrBrHH

Br HH Br

BrHHBr

1 2 3 4


Structures 1 and 2 are enantiomers; structures 3 and 4 are also enantiomers

Structures 1 and 3 are stereoisomers and they are not mirror images of each other. They are diastereomers• Diastereomers have different physical

properties - different melting points and boiling points, different solubilities, and so forth

Br BrH H

BrBrHH

Br HH Br

BrHHBr

1 2 3 4


Diastereomers●Stereoisomers that are not

enantiomers

●Unlike enantiomers, diastereomers usually have substantially different chemical and physical properties


C H

C HCH3

Cl

Br

HOCH

CHCH3

Cl

Br

OH(I) (II )

C H

C HHO

Cl

Br

CH3

CH

CHOH

Cl

Br

CH3(III ) (IV)

(I) & (II) are enantiomers of each other

(III) & (IV) are enantiomers of each other


C H

C HCH3

Cl

Br

HOCH

CHCH3

Cl

Br

OH(I) (II )

C H

C HHO

Cl

Br

CH3

CH

CHOH

Cl

Br

CH3(III ) (IV)

Diastereomers of each other:●(I) & (III), (I) & (IV), (II) & (III),

(II) & (IV)


12B. Meso Compounds

Compounds with two stereocenters do not always have four stereoisomers (22 = 4) since some molecules are achiral (not chiral), even though they contain stereocenters

For example, 2,3-dichlorobutane has two stereocenters, but only has 3 stereoisomers (not 4)


C Br

C BrH

CH3

H

CH3

CBr

CBrH

CH3

H

CH3(I) (II )

C Br

C BrCH3

CH3

H

HCBr

CBrCH3

CH3

H

H(III ) (IV)

Note: (III) contains a plane of symmetry, is a meso compound, and is achiral([a] = 0o).


C Br

C BrH

CH3

H

CH3

CBr

CBrH

CH3

H

CH3(I) (II )

C Br

C BrCH3

CH3

H

HCBr

CBrCH3

CH3

H

H(III ) (IV)

(I) & (II) are enantiomers of each other and chiral

(III) & (IV) are identical and achiral


C Br

C BrH

CH3

H

CH3

CBr

CBrH

CH3

H

CH3(I) (II )

C Br

C BrCH3

CH3

H

HCBr

CBrCH3

CH3

H

H(III ) (IV)

(I) & (III), (II) & (III) are diastereomers

Only 3 stereoisomers:●(I) & (II) {enantiomers}, (III) =

(IV) {meso}


12C. How to Name Compounds withMore than One Chirality Center

2,3-Dibromobutane

●Look through C2–Ha bond

HbBrHa Br

1

2 3

4

C C

Br Ha

12

3

(H, H, H) (Br, C, H)

①④

②③C2: (R) configuration


C C

Br Hb

23

4

(H, H, H) (Br, C, H)

●Look through C3–Hb bond

CH3

HaHbBr

CH3

Br1

23 4

①④

②③

C3: (R) configuration

●Full name: (2R, 3R)-2,3-Dibromobutane


13.Fischer Projection Formulas13A. How To Draw and Use Fischer

Projections

H3C

Ph

COOH

HOEt Br

Et OH

Br Ph

CH3

COOH

Et OH

Br Ph

CH3

COOH

FischerProjection


Ph

H

COOH

HMe OH

Me H

HO H

Ph

COOH

Me H

HO H

Ph

COOH

FischerProjection

PhCOOH

H Me

OHH


H3C

Cl

CH3

HCl H

(I)(2S, 3S)-Dichlorobutane

Cl H

H Cl

CH3

CH3

CH3

Cl

H3C

HClH

(II)(2R, 3R)-Dichlorobutane

H Cl

Cl H

CH3

CH3

mirror

enantiomers

(I) and (II) are both chiral and they are enantiomers of each other


H3C

Cl

CH3

ClH H

(III)(2S, 3R)-Dichlorobutane

H Cl

H Cl

CH3

CH3

(III) is achiral (a meso compound) (III) and (I) are diastereomers of

each other

Plane ofsymmetry


14.Stereoisomerism of CyclicCompounds

Me

H Me

H Me

H Me

H

mirror

enantiomers

H

Me Me

H

Plane ofsymmetry

a meso compoundachiral


14A. Cyclohexane Derivatives

Me

Me

Me

Me

1,4-Dimethylcyclohexane

Plane ofsymmetry

H

Me

Me

H

H

Me

H

Me

cis-1,4-dimethylcyclohexane

trans-1,4-dimethylcyclohexane

• Both cis- & trans-1,4-dimethylcyclo-hexanes are achiral and optically inactive

• The cis & trans forms are diastereomers


Me Me**


1,3-DimethylcyclohexanePlane of

symmetry

(meso)

H

Me

H

Me

●cis-1,3-Dimethylcyclohexane has a plane of symmetry and is a meso compound


Me Me**



NO plane of symmetry

enantiomers

H

Me

Me

HH

Me

Me

H

●trans-1,3-Dimethylcyclohexane exists as a pair of enantiomers


1,3-Dimethylcyclohexane●Has two chirality centers but

only three stereoisomers

(meso)

H

Me

H

Me


enantiomers

H

Me

Me

HH

Me

Me

H




enantiomers

H

H

MeMe

H

H

MeMe

●trans-1,2-Dimethylcyclohexane exists as a pair of enantiomers

mirror


1,2-Dimethylcyclohexane●With cis-1,2-

dimethylcyclohexane the situation is quite complicated

Me

H

MeH

Me

H

MeH

(I) (II)

●(I) and (II) are enantiomers to each other

mirror


●However, (II) can rapidly be interconverted to (III) by a ring flip Me

H

MeH

12

Me

H

MeH

(I) (II)

1'

2'mirror

H

Me 12

Me

H(III)


●Rotation of (III) along the vertical axis gives (I)

Me

H

MeH

12

H

Me12

Me

H

Me

H

MeH

(I) (II)

(III)

1'

2'

C1 of (II) and (III) become C2’ of (I) & C2 of (II) and (III) become C1’ of (I)


Me

H

MeH

12

H

Me12

Me

H

Me

H

MeH

(I) (II)

(III)

1'

2'

Although (I) and (II) are enantiomers to each other, they can interconvert rapidly (I) and (II) are achiral


15.Relating Configurations throughReactions in Which No Bonds tothe Chirality Center Are Broken

A reaction is said to proceed with retention of configuration at a chirality center if no bonds to the chirality center are broken. This is true even if the R,S designation for the chirality center changes because the relative priorities of groups around it changes as a result of the reaction


H

O

Me H

HOH

Me HH

NaBH4

MeOH

Ph Br

NaCN

DMSO

Me H

Ph CN

Me H

Same configuration

Same configuration


15A. Relative & Absolute Configurations Chirality centers in different molecules

have the same relative configuration if they share three groups in common and if these groups with the central carbon can be superimposed in a pyramidal arrangement Y

AB

CX

AB

C

The chirality centersin I and II have thesame relativeconfiguration. Theircommon groups andcentral carbon canbe superimposed.

I

II


The absolute configuration of a chirality center is its (R) or (S) designation, which can only be specified by knowledge of the actual arrangement of groups in space at the chirality center(R)-2-Butanol (S)-2-Butanol

HO H H OH

enantiomers


16.Separation of Enantiomers:Resolution

e.g.R R'

OH

*(racemic)

ClOMe

O

Ph CF3

(Mosher acidchloride)

R R'

O

OOMe

PhCF3

R R'

O

OOMe

PhCF3+

( 1 : 1 )

diastereomers

usually separable either by flash column

chromatography or recrystallization etc.

Resolution – separation of two enantiomers


Kinetic Resolution

R2

R1R

OH

*R2

R1R

OH

*R2

R1R

OH

*O

+

(racemic)

●One enantiomer reacts “fast” and another enantiomer reacts “slow”


e.g.Me3Si

C5H11

OH*

(racemic)

tBuOOH, Ti(OiPr)4

(-)-DET

Me3Si

C5H11

OH

Me3Si

C5H11

OHO+

42%(99%ee)

43%(99%ee)

Me3Si

OHR'

H

Me3Si

OHH

R'

S R

* stop reaction at 50%* maximum yield = 50%

(-)-DET:COOEt

COOEtHO

HO

(D)-(-)-Diethyl Tartrate


17.Compounds with ChiralityCenters Other than Carbon

R1

SiR2

R4 R3

R1

GeR2

H R3

R1

NR2

R4 R3

X SR2 R1

O


18.Chiral Molecules That Do NotPossess a Chirality Center

P(Ph)2

P(Ph)2

(Ph)2P

(Ph)2P

(S)-BINAP (R)-BINAP

enantiomers


enantiomers

C C

Cl

H

CCl

HCC

Cl

H

CCl

H

mirror


END OF CHAPTER 5

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Created by Professor William Tam & Dr. Phillis Chang Chapter 5 Stereochemistry Chiral Molecules...

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