- Stereoisomers are molecules with the same molecular formula but different arrangements of atoms in space. There are two main types of isomerism: positional isomers and stereoisomers. - Stereoisomers include geometric isomers and optical isomers. Geometric isomers have the same connectivity but different spatial arrangements, and require a double bond or ring structure. Cis isomers have substituents on the same side, trans on opposite sides. - The E/Z system names geometric isomers based on atomic number priorities using Cahn-Ingold-Prelog rules, with "Z" denoting same-side priority and "E" opposite sides.

1. http://lawrencekok.blogspot.com
Prepared by
Lawrence Kok
Tutorial on Stereoisomers, Cis Trans, E/Z, Optical
Isomerism and Polarimetry.

2. IsomerismMolecules with same molecular formula but diff arrangement of atom
Two types of Isomerism
Positional Chain Isomer Functional Gp Isomer
C – C – C – C – OH
C4H10O1
Structural Isomerism
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom
Diff hydrocarbon chain skeleton
• Same molecular formula
• Same structural formula/ same connectivity
• Diff spatial arrangement of atom
Stereoisomerism
Hydrocarbon Chain Isomer
Diff functional gp position Diff functional gp
C – C – C – OH
‫׀‬
CH3
C – C – C –C
‫׀‬
OH
C – C – C – C
‫׀‬
OH
C – C – C – C
‫׀‬
OH
C – C – C – O – C
Optical IsomerGeometric Isomer
Click here khan organic videos.
Compound Ethane Ethanoic acid
Empirical formula CH3 CH2O
Molecular formula C2H6 C2H4O2
Full SF
Condensed SF CH3CH3 CH3COOH
Stereochemical
formula
(3D)
Isomer Physical
property
Chemical
property
Structural isomer
- Hydrocarbon chain
- Functional gp position
- Functional gp
Different
Different
Different
Similar
Similar
Different
Geometrical isomer Different Similar
Optical isomer Similar Similar
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
H O
‫׀‬ ‖
H - C - C - OH
‫׀‬
H
Structural formula – arrangement atoms in molecule (2/3D)
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
CH3CH3
ethane
Display full SF Condensed SF Ball/stick model Spacefilling
Click here chemical search.
same connectivity but
diff spatial arrangement

3. CI
Isomerism
Two types of Isomerism
Positional
Chain Isomer
Functional
Gp Isomer
C4H10O1
Structural Isomerism
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom
• Same molecular formula
• Same structural formula/same connectivity
• Diff spatial arrangement of atom
Stereoisomerism
Hydrocarbon
Chain Isomer
Optical IsomerGeometric Isomer
Requirement for geometric isomers
• Presence of C=C double bond - prevent bond rotation
• Presence of ring structure - prevent bond rotation
• Carbon atom in double bond bonded to diff atom
Cis Isomers
Atom located on same side
Trans Isomers
Atom located on diff side
Presence C=C Presence of ring structure
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
Cis 1, 2 dichloroethene
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
Trans 1, 2 dichloroethene
Cis 1, 2 dichlorocyclopropane Trans 1, 2 dichlorocyclopropane
Carbon atom bond to diff atom
double bond
C – C – C – C – OH C – C – C –C
‫׀‬
OH
C – C – C – O – C
C – C – C – OH
‫׀‬
CH3
CI CI CI
CI
H
HHH
CI
CI
H
H
H
H
CI
Cis 1, 3 dichlorocyclobutane Trans 1, 3 dichlorocyclobutane
same
atom
different
atomχ
✓
No geometric
isomers
Geometric
isomers
same connectivity but
diff spatial arrangement

4. • Same molecular formula
• Same structural formula/same connectivity
• Diff spatial arrangement of atom
Stereoisomerism
Geometric Isomer
Requirement for geometric isomers
• Presence of C=C double bond - prevent bond rotation
• Presence of ring structure - prevent bond rotation
• Carbon atom in double bond bond to diff atom
Cis Isomers
Atom located on same side
Trans Isomers
Atom located on diff side
Presence C=C Presence of ring structure
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
Cis 1, 2 dichloroethene
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
Trans 1, 2 dichloroethene
Cis 1, 2 dichlorocyclopropane Trans 1, 2 dichlorocyclopropane
Carbon atom bond to diff atom
double bond
CI CI CI
CI
H
HHH
same
atom
different
atom
Cis / Trans
naming sys
click here E/Z naming system
2 diff substituent
on each carbon
[Z] 1, 2 dichloroethene [E] 1, 2 dichloroethene
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
Atom same side Atom opposite side
[Z] 1, 2 dichlorocyclopropane [E] 1, 2 dichlorocyclopropane
E / Z
naming sys
E/Z (CIP priority)
4 diff substituents
1
1 – high priority
2 – low priority
1
2
1
2 2
2
1
Priority same side – Z
Priority opp side - E
H H
CICI
1 1
2 2
H CI
CI H
1
1 2
2
1 – high priority
2 – low priority
Priority same side – Z
Priority opp side - E
E/Z naming system
↓
Cahn-Ingold-Prelog (CIP)
CH3 H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br OH
1 – high priority
2 – low priority
Priority same side – Z
Priority opp side - E
1
2
1
2C atomic
mass ↓
Br atomic
mass ↑
O atomic
mass ↑
H atomic
mass ↓
Priority same side - Z

5. same
atom
different
atom
Cis / Trans
naming sys
click here E/Z naming system
2 diff substituent
on each carbon
[Z] 1, 2 dichloroethene [E] 1, 2 dichloroethene
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
[Z] 1, 2 dichlorocyclopropane [E] 1, 2 dichlorocyclopropane
E / Z
naming sys
E/Z (CIP priority)
4 diff substituents
1
1 – high priority
2 – low priority
1
2
1
2 2
2
1
Priority same side – Z
Priority opp side - E
H H
CICI
1 1
2 2
H CI
CI H
1
1 2
2
1 – high priority
2 – low priority
Priority same side – Z
Priority opp side - E
E/Z naming system Cahn-Ingold-Prelog (CIP)
CH3 H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br OH
1 – high priority
2 – low priority
Priority same side – Z
Priority opp side - E
1
2
1
2C atomic
mass ↓
Br atomic
mass ↑
O atomic
mass ↑
H atomic
mass ↓
Priority same side - Z
CI I
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H Br
CH3 CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
[E] 2-chlorobut-2-ene
Cis 2 chlorobut-2-ene
[Z] 2-bromo-1-chloro-2-iodoethene
CI Br
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H I
[E] 2-bromo-1-chloro-2-iodoethene
Br atomic
mass ↓
H atomic
mass ↓
I atomic
mass ↑
2
2
1 1
CI atomic
mass ↑
CI atomic
mass ↑
I atomic
mass ↑
Br atomic
mass ↓
1
1
2
2
H atomic
mass ↓
CH3 CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CH3
[Z] 2-chlorobut-2-ene
Trans 2 chlorobut-2-ene
based on atomic mass
1 1
2 2 1
1 2
2

6. CH3 CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H C2H5
Br CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H C2H5
H CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br C2H5
CH3 H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br OH
1
1 2
2 1
1
22
E/Z naming system Cahn-Ingold-Prelog (CIP)
H COOH
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
HOOC H
1 – high priority
2 – low priority
Priority same side – Z
Priority opp side - E
1
1
2
2
H atomic
mass ↓
C atomic
mass ↑
C atomic
mass ↑
H atomic
mass ↓
Br H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3 OH
H atomic
mass ↓
C atomic
mass ↓
O atomic
mass ↑1 1
2 2
Br atomic
mass ↑
Br atomic
mass ↑
O atomic
mass ↑
H atomic
mass ↓
1 2
2
C atomic
mass ↓
based on atomic mass
2
11
2
1
1 2
2
1
E - Priority opposite side Z - Priority same side E - Priority opposite side
Trans but-2-ene-1,4-dioic acid
[Z] 1-bromo-2-methylbut-1-ene
Br atomic
mass ↑
H atomic
mass ↓
H H
‫׀‬ ‫׀‬
C – C – H
‫׀‬ ‫׀‬
H H
H
‫׀‬
C – H
‫׀‬
H
[E] 1-bromo-2-methylbut-1-ene
Br atomic
mass ↑
H atomic
mass ↓
H H
‫׀‬ ‫׀‬
C – C – H
‫׀‬ ‫׀‬
H H
C – bond H, H, C
(Higher priority)
H
‫׀‬
C – H
‫׀‬
H
C – bond H, H, H
(Lower priority)
[E] 3-methylpent-2-ene
C atomic
mass ↑
H atomic
mass ↓
H H
‫׀‬ ‫׀‬
C – C – H
‫׀‬ ‫׀‬
H H
C – bond H, H, C
(Higher priority)
C – bond H, H, C
(Higher priority)
C – bond H, H, H
(Lower priority)
C – bond H, H, H
(Lower priority)
H
‫׀‬
C – H
‫׀‬
H
[Z] 3-methylpent-2-ene
H CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3 C2H5
H atomic
mass ↓
C atomic
mass ↑
H H
‫׀‬ ‫׀‬
C – C – H
‫׀‬ ‫׀‬
H H
H
‫׀‬
C – H
‫׀‬
H
C – bond H, H, C
(Higher priority)
C – bond H, H, H
(Lower priority)

7. CH3 H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H C2H5
CH3 CH2OH
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3CH2 CHO
Br CH2OH
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CI CHO
CI CH2OH
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br CHO
CH3 H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br OH
1
22
1
E/Z naming system Cahn-Ingold-Prelog (CIP)
H COOH
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
HOOC H
1 – high priority
2 – low priority
Priority same side – Z
Priority opp side - E
1
1
2
2
H atomic
mass ↓
C atomic
mass ↑
C atomic
mass ↑
H atomic
mass ↓
Br H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3 OH
H atomic
mass ↓
C atomic
mass ↓
O atomic
mass ↑1 1
2 2
Br atomic
mass ↑
Br atomic
mass ↑
O atomic
mass ↑
H atomic
mass ↓
1 2
2
C atomic
mass ↓
based on atomic mass
2
11
2
1
1
2
2
1
E - Priority opposite side Z - Priority same side E - Priority opposite side
Trans but-2-ene-1,4-dioic acid
Br atomic
mass ↑
CI atomic
mass ↓
H
‫׀‬
C = O
H
‫׀‬
C – H
‫׀‬
OH
Br atomic
mass ↑
CI atomic
mass ↓
C – bond H, O, O
(Higher priority)
H
‫׀‬
C – OH
‫׀‬
H
C – bond H, O, O
(Higher priority)
C – bond H, O, O
(Higher priority)
C – bond H, O, H
(Lower priority)
C – bond H, O, H
(Lower priority)
H
‫׀‬
C = O
H H
‫׀‬ ‫׀‬
H – C – C
‫׀‬ ‫׀‬
H H
H
‫׀‬
H – C
‫׀‬
H
C – bond H, H, H
(Lower priority)
Z - Priority same side
H
‫׀‬
C = O
H
‫׀‬
C – H
‫׀‬
OH
C – bond H, O, H
(Lower priority)
E - Priority opposite side
C – bond H, H, C
(Higher priority)
Z - Priority same side
Pent – 2-ene 2,3-dichlorobut-2-ene
H H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3 C2H5
[E]-2,3 dichloro
but-2-ene
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3 CH3
CH3 CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CI CH3
2 2 2
2
2
22 21 1
1
1
1
1
1 1
[Z] pent-2-ene [E] pent-2-ene [Z]-2,3 dichloro
but-2-ene
Draw and name isomers using E/Z convention

8. Draw structural formula isomer with MF below, state type of isomerism
Stereoisomerism
C2 H2 CI2
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CI H
Both Structural formula
Geometric Isomer
CI CI
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
Cis 1, 2 dichloroethene Trans 1, 2 dichloroethene
[Z] 1, 2 dichloroethene [E] 1, 2 dichloroethene
22
11
2
2
1
1
C3H4CI2
CI
CI
CI CI
H HH
H
Both Structural
formula
CICICI
Geometric
Isomer
HHH CI
H
Cis 1, 2 dichlorocyclo
propane
Trans 1, 2 dichlorocyclo
propane
[Z] 1, 2 dichlorocyclo
propane
[E] 1, 2 dichlorocyclo
propane
Which exhibit cis/trans isomerism ?
CI H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br H
F CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H CI
F CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CI CH3
CH3CH=CHCH3CH3CH=CH2
CH(F)=C(CH3)2 CH(CI)=C(CI)CH3
Draw geometric isomers
CH3CH=CHCH2CH3
FCH = CHF
Which is structural isomer CH3COCH2CH3
H H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
CH3 C2H5
CH3 H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H C2H5
F F
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
F H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H F
Which exhibit cis/trans isomerism ?
CH3CH=CHCH2CH3
FCH = CHF
Cis/ [Z] Cis/ [Z]Trans / [E] Trans / [E]
CH3CH2-O-CH2CH3CH3CH2CH2-CH
‖
O
CH2=CH-CH-CH3
‫׀‬
OH

9. Geometric Isomers Optical Isomers
Same chemical property– Same functional gp
• Diff physical property – Diff spatial arrangement
(Diff density, solubility, melting pt/boiling pt)
• Same chemical property – Same functional gp
• Same physical property
(Same density, solubility, melting pt/boiling pt)
Vs
Enantiomer
Mirror image of each other
Enantiomer
Mirror image of each other
Stereoisomerism
Molecules with same molecular formula but diff spatial arrangement
• Same molecular formula
• Same structural formula / same connectivity
• Diff spatial arrangement of atom
Cis Isomer
Atom on same side
Trans Isomer
Atom on diff side
click here for optical rotation sugar click here for polarimeter
click here opical rotation corn syrupclick here polarimeter Pasco Demo
Mirror image
Right handed Left handed
Non superimposable
Chiral/asymmetrical/stereocentre carbon
(4 diff groups)
same connectivity but
diff spatial arrangement

10. Isomers with same Molecular Formula and Structural Formula but diff spatial arrangement
• At least 1 asymmetric / chiral carbon / stereocentre , bonded to 4 diff gp
• NH2CH(R)COOH show optical isomerism
• Optical isomers/mirror images call enantiomers (cannot superimpose on each other)
• Similar physical and chemical property except for the effect on rotation of plane of polarised light
• Optically active – enantiomer rotate plane polarised light to one direction (clockwise / anticlockwise)
• Optically inactive – enantiomer present in equal amt (equimolar) – racemic mix and rotation cancel out each other
Optical Isomers
chiral carbon – 4 diff gp
Optically inactive – Rotation cancel out each other
Enantiomer (R) - rotate clockwise Enantiomer (S) – rotate anticlock wise
50% 50% 70% 30%
Optically active – Net Rotation clockwise
Non superimposable
Non superimposable

11. 1. Light pass through 1st polariser – plane polarised light produced
2. Sample introduce to tube. Sample is optically active
Rotate plane of polarised light to one direction
3. Turn analyzer either clockwise/anticlock wise to give light of max intensity again
4. If sample rotate light 120 clockwise – Analyzer need to rotate anticlock wise 120
5. If one enantiomer rotate light 120 clockwise
Another enantiomer rotate light anticlock wise 120
How polarimeter detect optical isomer ?
6. Racemic Mix = enantiomers in equal amt (equimolar) , cancel each other rotation
1st polarizer
1st polarizer
sample optically active
sample optically inactive= Optical activity ability- to rotate plane of polarised light
Optically active isomers
–presence of asymmetrical/chiral centre
- carbon bond to 4 diff gp
Product from natural sources/catalysed by enzyme
• give 1 pure optically active enantiomer
• chiral and found in single enantiomer – optically active
Products synthesised chemically
• give 2 enantiomer in equal amt /racemic mix
• optically inactive rotation cancel out each other
Light source
1st polarizer
Tube containing sample
which able to rotate
polarized light
2nd polarizer
(Analyzer)
Polarizer
tube
Rotated clockwise
How Polarimeter works ?
R – inactive
Racemate mix ibuprofen
S – active
Racemate mix ibuprofenIbuprofen (painkiller)
Click here notes isomers
R limonene S limonene
CH3
CH3
CH3

12. Product from natural source/catalysed by enzyme
• give 1 pure optically active enantiomer
• chiral and found in single enantiomer – optically active
Product synthesised chemically
• give 2 enantiomer in equal amt /racemic mix
• optically inactive rotation cancel out each other
R – inactive
Racemate mix ibuprofen
S – active
Racemate mix ibuprofen
Ibuprofen
(painkiller) R limonene S limonene
CH3
CH3
CH3
Stereoisomerism
Mirror image / enantiomers
Same chemical/physical property
except rotation of polarized light
Source/smell
orange
Source/smell
lemon
Mirror image / enantiomers
Same chemical/physical property
except rotation of polarized light
R carvone S carvone
Mirror image / enantiomers
Same chemical/physical property
except rotation of polarized light
Source/smell
spearmint
Source/smell
caraway seed
R Thalidomide (sedative) S Thalidomide (teratogenic)
• Drug company make drug with R and S (racemic mix)
• Thalidomide exist as optical isomers
• Enantiomers (R) and (S)
• (R) effective against morning sickness
• S teratogenic, birth and limb defect
Our body synthesise enzyme which have active site for only one enantiomer
Mirror image / enantiomers
Thalidomide
(pregnancy)
• (S) cause limb defect / shortening of arm /leg
• (R) is effective drug
• Body convert (R) to (S) by racemisation process, produce racemic mix (R)/(S)
• Most drug in racemic mix equal (R) and (S)
• Cheaper to synthesise racemic mix than pure enantiomer
• Single enantiomer appear to be more effective than racemic mix
• Clinical trial is essential to ensure no harmful side effect
(S), effective as pain relief
(R) has no side effect!

13. March 2010 - Published in Science by Takumi Ito.
Click HERE for info
Defect Limb due to Thalidomide
• (S) bind /inactivate protein cereblon, which involve in limb formation.
• Inactivation, lead to a teratogenic effect on LIMB DEFORMITIES
Published in Science .....
• Hiroshi Handa /Takumi Ito - Developed tiny beads with Thalidomide attach.
• Thalidomide beads mix with cells extract
• Protein Cereblon was bounded on beads
• Lack Protein Cereblon during embryo development, cause limb deformities
Click HERE for info/source
http://www.rsc.org/chemistryworld/news/2010/march/11031001.asp
http://news.bbc.co.uk/2/hi/science/nature/8562998.stm
http://news.sciencemag.org/sciencenow/2010/03/-thalidomide-ranks-as-one.html
Scientist discovered how Thalidomide caused Malformed Limb
History of Thalidomide
1954 - Thalidomide for morning sickness.
1961 - Withdrawn, teratogenicity, birth defects result .
1990 - FDA approved for leprosy (skin disease)
1998 - FDA approved for multiple myeloma, (cancer of plasma cells in blood)
2004 - Lenalidomide derived from Thalido able to strengthen immune cells
and effective against blood cancers
2011 - Thalidomide + Lenalidomide inhibit formation of new blood vessels
( anti-angiogenic) of tumor cells, Tumors unable to grow due to lack of nutrition.
Researchers testing thalidomide in trials for other HIV and Crohn’s disease.

14. Write structural formula isomers for C4H9OH, state which isomer show optical isomerism
Butan -1-ol Butan-2-ol 2-methylpropan-2-ol 2-methylpropan-1-ol
All structural isomers
Stereoisomers (Optical Isomers)
Write structural formula of cyclic isomers for C3H4CI2, state type of isomerism
Structural formula
Geometric Isomers
Cis/Tans isomerism
Optical Isomers
Enantiomer, mirror image
Cyclic ring
geometric isomers
CH3-CH2-CH2-CH3
‫׀‬
OH
CH3-CH2-CH-CH3
‫׀‬
OH
CH3
‫׀‬
CH3-C-OH
‫׀‬
CH3
CH3-CH-CH2-OH
‫׀‬
CH3
chiral centre
chiral centre
CI CI
CI
CI
H
HHH
H
HHH CI
CICICI
Trans 1, 2 dichlorocyclopropaneCis 1, 2 dichlorocyclopropane
Stereoisomers (Optical Isomers)
CICI CICI
H HHH
chiral centre chiral centre
* *

15. Optical Isomerism
Which carbon has chiral center?
Draw all stereoisomers CHBr=CHCH(OH)CH3
CHBr=CHCH(OH)CH3
Optical isomersGeometric isomers
Chiral carbon with 4 diff gpDouble bond prevent bond rotation
Cis / Z Trans / E
CH3CH2C*
H(CH3)(CI) CH3C*
H(NH2)COOH CH3C*
H(OH)CH2OH C2H5C*
H(OH)CH2OH
C2H5
H H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br CH(OH)CH3
H CH(OH)CH3
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
Br H
H
‫׀‬
CHBr=CH-C–CH3
‫׀‬
OH
H
‫׀‬
CH3-C-CH=CHBr
‫׀‬
OH
R (enantiomer) S (enantiomer)
chiral centre
Non chiral centre
NOT mirror image
superimposable
χ
rotate it
They are same. Superimposable
Mirror image
Non superimposable
chiral centre

16. Optical Isomers
Enantiomers Diastereomers
Same connectivity
Have chiral carbon
Non superimposable
Mirror image each other
Same connectivity
Have chiral carbon
Non superimposable
No Mirror image
diff chemical/physical property
2 chiral centre 22 = 4 stereoisomer
3 chiral centre 23 = 8 stereoisomer
click here to view diastereomers
same chemical/physical property
Mirror image
Not Mirror image
diff configuration at one or more
of equivalent stereocentre
chiral centre
not mirror image
same configuration
mirror image
diff configuration
2, 3 - dibromopentane
Diastereomers
A B C D
Enantiomer/mirror image Enantiomer/mirror image
Diastereomer/NOT mirror image
Enantiomer/mirror image
Diastereomer/NOT mirror image
2n n = chiral centre

17. Isomers with same Molecular Formula and Structural Formula but diff spatial arrangement
• At least 1 asymmetric / chiral carbon / stereocentre , bonded to 4 diff gp
• NH2CH(R)COOH show optical isomerism
• Optical isomers/mirror images call enantiomers (cannot superimpose on each other)
Optical Isomers
chiral carbon – 4 diff gp
Non superimposable
Non superimposable
click here diastereomers
Optical Isomers
Enantiomers Diastereomers
Same connectivity
Have chiral carbon
Non superimposable
Mirror image each other
Same connectivity
Have chiral carbon
Non superimposable
No Mirror image
diff chemical/physical property
click here diastereomers
same chemical/physical property
Mirror image Not Mirror image
diff configuration at one or more
of equivalent stereocentre
chiral centre
not mirror image
same configuration
mirror image
diff configuration
Video on diastereomers

18. Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenses
http://creativecommons.org/licenses/
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorial
http://lawrencekok.blogspot.com