Unit-III Stereoisomerism.ppt

Useful poc 2 ppt

1. STEREOISOMERISM
Prepared by
Mr. Sandip N Wagh
Assistant professor
Department of Pharmaceutical Chemistry
SNJB’s SSDJ College of Pharmacy, Chandwad

2. ELEMENTSOFSYMMETRY
•Enatiomerismdependsonwhetheramoleculein not
superimposableonitsmirrorimage.Ifitis
superimposable, the moleculeis optically inactive
otherwise is optically active. The most convenient
methodofinspectingsuperimposabilityisto
determinewhetherthemoleculehasanyofthe
following fourelementsofsymmetry:
1.Planeofsymmetry(s)
2.Centreofsymmetry(i)
3.Simpleorproperaxisofsymmetry(C
n)
4.Alternatingorimproperaxisofsymmetry(S
n)
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 2

3. Planeofsymmetry(s)
•Aplaneofsymmetryisdefinedasanimaginaryplanewhich
dividesamoleculeinsuchawaythatonehalfismirrorimage
oftheotherhalf.
•Amoleculewithatleastaplaneofsymmetrycanbe
superimposedonitsmirrorimageandisachiral.Amolecule
thatdoesnothaveaplaneofsymmetryisusuallychiral;it
cannotbesuperimposeduponitsmirrorimage.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 3
COOH
OH
OH
H
H
COOH
Plane of
symmetry
•A plan of symmetry may
pass through atoms,
between atoms or both.

4. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 4
2. Centreofsymmetryorinversion(i)or(C
i)
•Acentreofsymmetry(centreofinversion)isdefinedasapoint
withinthemoleculesuchthatifanatomisjoinedtoitbya
straightlinewhichifextrapolatedtoanequaldistancebeyondit
inoppositedirectionmeetsanequivalentatom.Inotherwords
itisapointatwhichallthestraightlinesjoiningidentical
pointsinthemoleculecrosseachother.
COOH
COOH
CH3
CH3
H
H H
H
Centre of
symmetry
2,4-Dimethylcyclobutane -
1,3-dicarboxylic acid has C
i

5. H
HH3C
CH3
NHCO
C C
NH CO
trans(achiral)
NHCO
C
NH CO
C
CH3H3C
HH
cis(chiral)

6. 3. Simpleorproperaxisofsymmetry(C
n)
•Animaginarylinepassingthroughthemoleculeinsucha
waythatwhenthemoleculeisrotatedaboutitbyan
angleof360
o/n,anarrangementindistinguishablefrom
theoriginalisobtained.Suchanaxisiscalledn-foldaxis
ofsymmetry.Forexample,cis-1,3-dimethylcyclobutane
hasatwofoldaxisofsymmetry(C
2)i.e.rotationby180
o
givesindistinguishableappearance.
HH
H CH3
H3C
H
Rotation
C2-Axis of
Symmetr
y
H3C
H H
H
H CH3
H
H
by180o
H
H

7. 4. Alternatingorimproperaxis of symmetry
(S
n)
Rotation
by90o
Reflaction
through mirror
plane
perpendicular to
axis of rotation
4
3
(a)
H3C
H
2
CH3
H
H
H
H
CH3
1
23
4
B
CH3
H
H
H
CH3
CH3
A
CH3
(a)
3 4
2 1
H
H3C
H
CH3
H
1
CH3
(b)
H
CH3
H3C
1,2,3,4-Tetramethyl-
cyclobutane has S4

8. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 8
•Chirality/Stereogenic Centers/Asymmtric
carbon/Chiral center/Chiral carbon
•Anobjectwhichcannotbesuperimposedonitsmirror-
imageissaidtobechrialandthepropertyofnon-
superimposabilityiscalledchirality.Thusourhandsare
chiral.
•
•Similarly, alphabets R,F,J are chiral and A, M, O are achiral.

9. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 9
•OThemostcommonfeaturethatleadstochiralityinorganiccompoundsisthe
presenceofanasymmetric(orchiral)carbonatom.
•OApointinamoleculewherefourdifferentgroups(oratoms)areattachedto
carboniscalledachiralcenter.
•OTherearetwonon-superimposablewaysthat4differentdifferentgroups(or
atoms)canbeattachedtoonecarbonatom.
•OIftwogroupsarethesame,thenthereisonlyoneway.
•OAchiralmoleculeusuallyhasatleastonechiralcenter.

10. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 10
•MolecularChiralityandAsymmetricCarbon
•Chiralityinmoleculesisusuallyduetothepresence
ofansp3carbonatomwithfourdifferentgroups
attachedtoit.Suchacarbonatomiscalledachiral
carbonorachiralitycentre.
•Thepresenceofachiralitycentreusuallyleadsto
molecularchirality.Suchamoleculehasnoplaneof
symmetryandexistsasapairofenantiomers.Such
acarbonatomissometimesalsoreferredtoas
asymmetriccarbonatom.

11. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 11
•AballandstickmodelofacompoundCwxyz
•Aderivativeofmethane,wherew,x,yandzarealldifferent
atomsorgroupsandamodelofitsmorrorimage.
C
X
Y
W W
Z
Mirror
C
X
Y
Z
•Wemaytwistandturntheabovetworepresentationsinany
waywelikesolongwedonotbreakanybond,yetwefindthat
thetwoarenotsuperimposable.Therefore,theymustrepresent
twoisomers,i.e.,twoenantiomers.

12. Enantiomers
W
C
X Y
W
C
X
Y
Z Z
non-superimposablemirrorimages
(alsocalledopticalisomers)
Pasteur decided that the molecules that made the crystals,
just asthe crystals themselves, must be mirror images.
Each crystal must contain a single type of enantiomer.

13. Pasteur’s hypothesis eventually led to the discovery
that tetravalent carbon atoms are tetrahedral.
Only tetrahedral geometry can lead to mirror image
molecules:
Squareplanar,squarepyrimidalortrigonalpyramid
willnotwork:
C
C C
tetrahedral
carbon
C
C
C
Van’t Hoff and
LeBel (1874)

14. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 14
AssymetricCenter
Chiralityisnot reservedjustfor objects-moleculescanbe chiral
•Chiral molecules-generallymoleculescontaininganasymmetriccenter
•Asymmetric(chiral)center-tetrahedralatombondedtofour differentgroups-indicated
with anasterisk (*)

15. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 15
Chirality
•Chiralobjectsareobjectswithleft-handedandright-handedforms
•Achiralobjects-objectsthathavesuperimposablemirrorimages.
•Nonsuperimposablemirrorimages -amirrorimage thatisnotthesameasthe
•image itself -chiralobjectshave nonsuperimposablemirrorimages

16. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 16
•A point in a molecule where four different groups (or atoms) are attached to carbon is called a Chiral
center.If two groups are the same, then there is only one way. A Chiral molecule usually has at least one Chiral
center.
CHIRALCENTERS
•AlwaysomitfromconsiderationallCatomsthatcannotbe tetrahedral
stereogenic centers. These include CH
2 and CH
3 groups, Any sp or sp
2
hybridized C

17. Achiral Molecules
•A molecule or object that is
superimposable on its mirror image is
said to beachiral.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
17
•We can now consider several molecules to
determine whether or not they are chiral.

18. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 18
•O In general, a molecule with no stereogenic centers will not be chiral.
•O With one stereogenic center, a molecule will always be chiral.
•O With two or more stereogenic centers, a molecule may or may not be chiral.
•O Achiral molecules usually contain a plane of symmetry but chiral molecules
do not.

19. Optical Activity
•Optical activity is the ability of a Chiral molecule to rotate the
plane of plane-polairsed light, measured using a polarimeter.
•PLANE POLARIZED LIGHT:
•light that has been passed through a nicol prism or other
polarizing medium so that all of the vibrations are in the same
plane.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 19
non-polarized polarized

20. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 20
•Polarimeter–aninstrumentusedtomeasureopticalactivity.
•Asimplepolarimeterconsistsofalightsource,polarizinglens,sampletubeand
analyzinglens.
lightsource sampletube
polarizer analyzer

21. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 21

22. •Dextrorotatory(+):Anopticallyactivecompoundthatrotatesplane
polarizedlightinaclockwisedirection.
•(+)or (d)donotconfusewithD
•Levorotatory(-):Anopticallyactivecompoundthatrotatesplanepolarized
lightinacounterclockwisedirection.
•(-)or (l) donotconfusewithL
•Theangleofrotationofplanepolarizedlightbyanopticallyactive
substanceisproportionaltothenumberofatomsinthepathofthelight.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 22
(+)/d-LacticAcid (-)/l-LacticAcid

23. •Specific rotation –the angle of rotation of plane polarized light by a 1.00 gram
per cm
-3
sample in a 1 dm tube. [α ]
D (D = sodium lamp, λ = 589 mμ).
•The more molecules of a chiral sample are present the greater the rotation of
the light = concentration dependent.
11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
23
D
(observed rotationindegrees)


(pathlength in dm)(concen trationing/ml)lC
[]
O where α = observedrotation
l = length(dm)
d = concentration(g/cc)
•SpecificRotationdependsonthenatureofsubstance,wavelengthoflightused,
concentrationofthesolution,thicknessofthelayer,natureofthesolventand
temperatureatwhichexperimentisconducted.

24. Enantiomerism
11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 24
Enantiomersarenon-superimposablemirrorimageisomers.
Enantiomersarerelatedtoeachothermuchlikearighthandisrelatedtoalefthand.
Enantiomersaresaidto beChiral.
sometimesthetermsright-handedandleft-handedareuseddescribecompoundswith
anasymmetriccarbon.

25. 11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 25
Characteristicfeaturesofenantiomers:
Enantiomershaveidenticalphysicalproperties(bp,mp,density,solubilityand
refractiveindex)butthereisadifferenceindirectionofrotationofplanepolarized
light. Property (+)-Lacticacid(-)-Lacticacid
Specificrotation +2.24º -2.24º
MeltingPoint 26ºC 26ºC
They have identical chemical properties except in chemical reactions with other
optically active compounds.
They have different biological properties
E.g. (+)-Dextrose plays an important role in animal metabolism, where as (-)-Dextrose
is not metabolized.
When equal quantities of enantiomers are mixed an optically inactive compound
racemic mixture is formed.

26. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 26
Properties ofEnantiomers
1.Enantiomershaveidenticalphysicalpropertiessuchasboilingpoints,
meltingpoints,refractiveindices,andsolubilitiesincommonsolvents
exceptopticalrotations.
1)Manyofthesepropertiesaredependentonthemagnitudeofthe
intermolecularforcesoperatingbetweenthemolecules,andformolecules
thataremirrorimagesofeachothertheseforceswillbeidentical.
2)Enantiomershaveidenticalinfraredspectra,ultravioletspectra,and
NMRspectraiftheyaremeasuredinachiralsolvents.
3)Enantiomershaveidenticalreactionrateswithachiralreagents.

27. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 27
2.Enantiomersshowdifferentbehavioronlywhentheyinteractwithotherchiral
substances.
1.Enantiomersshowdifferentratesofreactiontowardotherchiralmolecules.
2.Enantiomersshowdifferentsolubilitiesinchiralsolventsthatconsistofasingle
enantiomeroranexcessofasingleenantiomer.
3.Enantiomersrotatetheplaneofplane-polarizedlightinequalamountsbutin
oppositedirections.
OSeparateenantiomersaresaidtobeopticallyactivecompounds.

28. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 28
Reactivitywithchiralmolecules….e.g.,enzymes, receptors, …..
drug action/metabolism
CH
2
Ph
H CH
3
I
CH
2
Ph
NHMe CH
3
II
(R)
H
( S )
MeNH
desoxyephedrine
Methamphetamine
10X more potent CNS
stimulant
Less cardiovascular

29. 11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
29
Whydochiralmoleculesreactdifferentlywithbiologicalmolecules?

30. DIASTEREOMERS
11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
30
Stereomersofasubstancethatarenotmirrorimagesofeachotheraretermedas
DiastereomersORDiastereomersarestereoisomersthatarenotmirrorimagesof
eachother–theyarestereoisomersthatarenotenantiomers.
They have different physical propertieslike m.p,b.p, solubility, density and
refractive index, etc.
Diastereomers have differentspecificrotation
but they mayhavesameor
opposite sign of rotation.

31. 11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
31
Cis-trans isomers are not mirror images, so these are diastereomers.
CC
H H
H3C CH3
cis-2-butene trans-2-butene
CC
H CH3
H3C H

32. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 32
Properties ofDiastereomers
•Diastereomers are similar, but they aren’t mirrorimages.
•Enantiomershaveoppositeconfigurationsatallchiralcenters;
Diastereomers are opposite at some, but not all chiralcenters.
•Diastereomers have different physicalproperties

33. MESOCOMPOUND
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 33
Amesocompoundisamoleculewithmultiplestereocentersthatis
superimposableonitsmirrorimage.
Mesocompoundsareachiralcompoundsthathas multiplechiralcenters.
Mesocompoundsareopticallyinactive.
Ithasaninternalsymmetry planethatdividesthecompoundin half.

34. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 34
Amesocompoundshouldcontaintwoormoreidenticalsubstitutedstereocenters.
Also,ithasaninternalsymmetryplanethatdividesthecompoundinhalf.These
twohalvesreflecteachotherbytheinternalmirror.Thestereochemistryof
stereocentersshould"cancelout".Whatitmeanshereisthatwhenwehavean
internalplanethatsplitsthecompoundintotwosymmetricalsides,the
stereochemistryofbothleftandrightsideshouldbeoppositetoeachother,and
therefore,resultinopticallyinactive.

35. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 35

36. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 36

37. Aslongasanyoneconformerof
planeofsymmetry,thecompound
acompoundhasa
willbeachiral.
plane of
symmetry
plane of
symmetry

38. D & L System of nomenclature of Optical
Isomer
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
38
ThefirstsystemfordoingthiswasdevelopedbyFischerandRosanoffaround
•1900.
Fischerfirstdevelopedamethodfordrawingcarbohydratesintwo-dimensions,
andaconventionwithrespecttoorientation,soastoindicatetheirthree
dimensionalstructures,so-calledFischerprojections.
FischerandRosanoffthendevisedanotationfordesignatingtheconfigurations
ofstereogeniccentres,depictedinFischerprojections,aseitherDorL.
The symbols D and L DO NOT relate to the sign of rotation of an optically active
molecule which is designated (+)-(or d) and (-)-(or l).

39. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
39
•Example:D(+)-glyceraldehydewasdefinedasbeingDbecause
theOHgroupattachedtotheC-2isontherighthandside(RHS)of
themoleculeswhendrawninitscorrectFischerprojection(in
whichtheCHOgroupappearsatthetop).
•ItsenantiomerL(-)-glyceraldehydewasdefinedasLbecausethe
OHgroupisonthelefthandside(LHS).

40. 11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 40
Incarbohydrates,ingeneral,theOHgroupattachedtothepenultimate
carbonatominthechaindeterminestheassignmentofDorL.Thus
(+)-glucosehastheD-configurationand(+)-ribosehastheL-
configuration.

41. 11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 41
Thenotationwasextendedtoa-aminoacids:Lenantiomersarethose
inwhichtheNH2groupisontheLHSoftheFischerprojectionin
whichthecarboxylgroupappearsatthetop.Conversely,theD
enantiomersarethoseinwhichtheNH2groupisontheRHS.Thus
(+)-alanineand(-)-serineareL-aminoacids.

42. Cahn-Ingold-Prelog sequencerules/R-S
NotationalSystem(R/S)
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 42
•AssigningtheAbsoluteConfiguration
1.UsetheCahn-Ingold-Prelogpriorityrulestoassignpriority(one
throughfour)tothefourgroupsonthe“chiral”atom.
2.Orientthemoleculesothatthelowestpriorityatomisintheback(away
fromyou).Lookattheremainingthreegroupsofpriority1-3.Ifthe
remainingthreegroupsarearrangedsothatthepriorities123areina
clockwisefashion,thenassignthechiralcenterasR(“rectus”orright).If
theremainingthreegroupsarearranged123inaanti-clockwise
manner,thenassignthechiralcenterasS(“sinister”orleft).

43. Cahn IngoldPrelog (CIP) sequence
rules:
•Sequencerule1:Eachatombondedtochiralcarbonis
assignedapriority.Priorityisbasedonatomicnumber;thehigher
theatomicnumber,thehigherthepriority.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 43

44. •Sequencerule2:Forisotopes,thehighertheatomicmass,the
higherthepriority.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 44

45. •Sequencerule3:Ifprioritycannotbeassignedonthebasisof
atomicnumberoratomicmassconsideringthefirstatomofa
group,thenlookatthenextsetofatomandcontinueuntila
prioritycanbeassigned.Priorityisassignedatthefirstpointof
difference.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
45

46. •Sequence rule 4:In the case of double bond and triple bonds,
atoms participating in the double or triple bond are considered to
be bonded to an equivalent number of similar atoms by single
bonds, that is, atoms of double and triple bonds are replicated.
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 46

47. High Priority to Low Priority
•-I, -Br, -Cl, -SH, -F, ,-OR , -OH, -NO2,
11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 47

48. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 48
CH
3
2COH
orient low est
priority group
aw ay
OH
H3C
2
H
1
OH
2
3
4H
1
COH
2
3
clockwise=R
orient lowest
priority group
away
OH
HO2C
H
1
OH
3
CH
3
CO2
H
2
4H
1
CH33
2
counterclockwise=S

49. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 49
Geometricalisomers
OCis–transisomers(alsocalledgeometricisomers)resultfrom
restrictedrotation.
ORestrictedrotationcanbecausedeitherbyadoublebondorbya
cyclicstructure.
OAsaresultoftherestrictedrotationaboutacarbon–carbondouble
bond,analkenesuchas2-pentenecanexistascisandtransisomers.
Thecisisomerhasthehydrogensonthesamesideofthedouble
bond,whereasthetransisomerhasthehydrogensonoppositesides
ofthedoublebond.

50. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 50
CIS
Groups/atoms are on the
SAME SIDE of the double
bond
TRANS
Groups/atoms are on
OPPOSITE SIDES across
the double bond

51. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 51
RESTRICTED ROTATION OF C=C BONDS
Singlecovalentbondscaneasilyrotate.Whatappearstobea
differentstructureinanalkaneisnot.Duetothewaystructures
arewrittenout,theyarethesame.
Allthesestructuresarethesamebecausec-cbondshave‘free’
rotation

52. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 52
RESTRICTED ROTATION OF C=C BONDS
C=Cbondshaverestrictedrotationsothegroupson
eitherendofthebondare‘frozen’inoneposition;it
isn’teasytoflipbetweenthetwo.
Thisproducestwopossibilities.Thetwostructurescannot
interchangeeasilysotheatomsinthetwomoleculesoccupy
differentpositionsinspace.

53. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 53
ISOMERISM
INBUTENE
O There are 3 structural isomers of C
4H
8 that are alkenes*. Of
these ONLY ONE exhibits geometrical isomerism.
BUT-1-ENE
cis BUT-2-
ENE
trans BUT-2-
ENE
2-
METHYLPROPENE

54. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 54
Cyclic compounds can also have cis and trans isomers.
The cis isomer has the hydrogens on the same side of the ring, whereas
the trans isomer has the hydrogens on opposite sides of the ring.

55. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 55
Properties of GeometricIsomers
O Geometricisomershavesimilarchemicalpropertiesbutsome
different physical properties.
O Symmetrical alkenes have the same groups or atoms attached to one
of the carbon atoms in the C=C bond.

56. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 56
E and ZBased onPriority:
Cahn-Ingold-Prelongrules:
1.Atomic Number
2.Atomic weight
3.Atomic number of the nextatom
O Higher priority at the opposite side of pi bond(E)
O Higher priority at the same side of pi bond(Z)

57. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 57
cis ortrans?

58. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 58

59. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 59

60. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 60

61. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 61
Syn addition is the addition of twosubstituentsto the same side
(orface) of adouble bondortriple bond, resulting in a decrease
inbond orderbut an increase in number of substituents.
Generally thesubstratewill be an alkene oralkyne.
An example of syn addition would be the oxidation of analkeneto a
diol via a suitable oxidizing agent such asosmium tetroxide, OsO
4,
orpotassium permanganate, KMnO
4.
Anti addition is in direct contrast to syn addition. In anti addition, two
substituents are added to opposite sides (or faces) of a double bond or
triple bond, once again resulting in a decrease in bond order and
increase in number of substituents.
Theclassicalexampleofthisisbromination(anyhalogenation)
ofalkenes.
Syn and Anti System

62. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 62

63. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 63
Syn addition reaction: Any atom and group are added to the reacting
molecule in the same phases then the addition is refer as syn addition.
Example:

64. 11 August 2022 SNJB's SSDJ College of Pharmacy, Chandwad (Nasik) 64
Anti addition reaction: Any atom and group are added to the
reacting molecule in the different phases then the addition is refer
as anti addition reaction.

65. 11 August 2022
SNJB's SSDJ College of Pharmacy, Chandwad (Nasik)
65