chem 2411 lecture 08 stereochemistry
TRANSCRIPT
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 1/60
Stereochemistry at Tetrahedral Centers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 2/60
Diferent Types o IsomerismDiferent Types o Isomerism
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 3/60
• Diferent order o connections gives diferent
carbon backbone and/or diferent unctionalgroups
Constitutional IsomersConstitutional Isomers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 4/60
StereochemistryStereochemistry
• For pharmaceuticals, slight diferences in 3D
spatial arrangement can make the diferencebeteen targeted treatment and undesired side!efects"
• #somers that have the same connectivity beteenatoms but diferent 3D, spatial arrangement otheir atoms are called STEREOisomers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 5/60
Stereochemistry o Organic CompoundsStereochemistry o Organic Compounds
Seager S$, Slabaugh %&, Chemistry or Today' (eneral, )rganic and *iochemistry, +th dition, -.0
Stereoisomers:
•Same molecular ormula
•Same seuence o bonded atoms 4constitution5,
•Diferent 3!D orientations o their atoms in space"Enantiomers: Stereoisomers that are mirror images o each other"
Diastereomers: Stereoisomers that difer at chiral centers, but no every chiral center"
enantiomers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 6/60
Stereochemistry o Organic CompoundsStereochemistry o Organic Compounds
Seager S$, Slabaugh %&, Chemistry or Today' (eneral, )rganic and *iochemistry, +th dition, -.
Chiral Carbon: Carbon in organic compound that has our diferent groupsattached to it"
Chirality: 67andedness8" &eers to compounds that cannot be superimposed onmirror image"
!De9ned relative to central, chiral atom 4carbon5
enantiomers
)7C
7
C )7
C7-)7
C7)
7
C7)
C7-)7)7C C
)7
C7-)
7
C7)C
7)
C7-)
7
Chiralcarbon
CHOindicatesaldehyde
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 7/60
Cis-trans IsomersCis-trans Isomers• C!C bonds that are constrained in a cyclic structure can not reely rotate
• To maintain orbital overlap in the pi bond, C:C double bonds can not reely rotate"
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 8/60
Cis-trans IsomersCis-trans Isomers
• ;ith rings and ith C:C double bonds, cis!
trans notation is used to distinguish beteenstereoisomers
• Cis < identical groups are positioned on the
S=% side o a ring• Trans < identical groups are positioned on
)>>)S#T sides o a ring
Copyright ? -.@ Aohn;iley B Sons, #nc" =ll lein, )rganic Chemistry -e@!
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 9/60
• #dentiy the olloing pairs as either
constitutional isomers, stereoisomers, oridentical"
"
-"
3"
IsomersIsomers
E"
@"
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 10/60
StereoisomersStereoisomers
• *eyond cis-trans isomers, there are many other
important stereoisomers• To identiy such stereoisomers, e must be able to
identiy chiral molecules
• = chiral ob1ect is )T identical to its mirror image
•
Gou are a chiral ob1ect" $ook in a mirror and raiseyour right hand" Gour mirror image raises his or herlet hand"
• Gou can test hether to ob1ects are identical byseeing i they are superimposable"
• Chirality is important in molecules" – *ecause to chiral molecules are mirror images, they ill
have many identical properties, but because they are notidentical, their pharmacology may be very diferent
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 11/60
• Some ob1ects are notthe same as theirmirror images4technically, they haveno plane o symmetry5
–
= right!hand glove isdiferent roma let!hand glove" Theproperty iscommonly called6handedness8
• )rganic molecules4including many drugs5have handedness thatresults romsubstitution patterns onsp3 hybridiHed carbon
StereochemistryStereochemistry
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 12/60
StereoisomersStereoisomers
• Chirality most oten results hen a carbon
atom is bonded to E uniue groups o atoms"
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 13/60
• Same connections, diferent spatial arrangement o atoms – nantiomers 4nonsuperimposable mirror images5
– Diastereomers 4all other stereoisomers5
• #ncludes cis, trans, con9gurational
StereoisomersStereoisomers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 14/60
• = point in a molecule here our diferent groups 4oratoms5 are attached to carbon is called a chirality
center stereocenter!"• There are to nonsuperimposable ays that E diferent
diferent groups 4or atoms5 can be attached to onecarbon atom
• = chiral molecule usually has at least one chirality center
Chirality CentersChirality Centers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 15/60
Chirality CentersChirality Centers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 16/60
StereoisomersStereoisomers
• #dentiy all o the chirality centers 4i any5 in
the olloing molecules
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 17/60
• %olecules that have one carbon ith E diferent
substituents have a nonsuperimposable mirrorimage < enantiomer
• *uild molecular models to see this
E#amples o EnantiomersE#amples o Enantiomers
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 18/60
• %olecules that are not superimposableith their mirror images are chiral 4havehandedness5
•
= plane o symmetry divides an entiremolecule into to pieces that are eIactmirror images
• = molecule ith a plane o symmetry is
the same as its mirror image and is said tobe achiral"
The Reason or $andedness: ChiralityThe Reason or $andedness: Chirality
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 19/60
• The plane has thesame thing on bothsides or the Jask
• There is no mirror
plane or a hand
%lane o Symmetry%lane o Symmetry
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 20/60
• (roups are considered 6diferent8 i there is anystructural variation 4i the groups could not besuperimposed i detached, they are diferent5
• #n cyclic molecules, e compare by olloing in
each direction in a ring
Chirality Centers in ChiralChirality Centers in Chiral
&olecules&olecules
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 21/60
Designating Con'gurationsDesignating Con'gurations
• nantiomers are )T identical, so they must
not have identical names
• Their names must be diferent, so e use theCahn!#ngold!>relog system to designate eachmolecule as either R or S"
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 22/60
Designating Con'gurationsDesignating Con'gurations
• The Cahn, #ngold and >relog system
" Ksing atomic numbers, prioritiHe the E groupsattached to the chirality center
-" =rrange the molecule in space so the loestpriority group aces aay rom you
3" Count the group priorities L-L3 to determinehether the order progresses in a clockise orcounterclockise direction
E" Clockise : R and Counterclockise : S
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 23/60
• The Cahn, #ngold and >relog system
" Ksing atomic numbers, prioritiHe the E groupsattached to the chirality center" The higher theatomic number, the higher the priority
– >rioritiHe the groups on this molecule
Designating Con'gurationsDesignating Con'gurations
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 24/60
Designating Con'gurationsDesignating Con'gurations
• The Cahn, #ngold and >relog system
-" =rrange the molecule in space so the loestpriority group aces aay rom you
– This is the step here it is most helpul to have ahandheld model
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 25/60
•
# a decision cannot be reached by ranking the 9rstatoms in the substituents, look at the second,third, or ourth atoms until diference is ound
Designating Con'gurationsDesignating Con'gurations
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 26/60
Designating Con'gurationsDesignating Con'gurations
• The Cahn, #ngold and >relog system
3" Counting the other group priorities, L-L3,determine hether the order progresses in aclockise or counterclockise direction
E" Clockise : R and Counterclockise : S
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 27/60
Designating Con'gurationsDesignating Con'gurations
• Designate each chirality center belo as
either R or S"
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 28/60
Designating Con'gurationsDesignating Con'gurations
• ;hen the groups attached to a chirality
center are similar, it can be tricky toprioritiHe them
• =nalyHe the atomic numbers one layer oatoms at a time
First layer
Second layer
E
Tie
- 3
• #s this moleculeR or SM
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 29/60
• =nalyHe the atomic numbers one layer o
atoms at a time• First layer
• Second layer
Designating Con'gurationsDesignating Con'gurations
E
Tie
- 3
• The priority is based on the 9rstpoint o diference, (OT thesum o the atomic numbers
• #s this molecule R or SM
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 30/60
Designating Con'gurationsDesignating Con'gurations
• ;hen prioritiHing or the Cahn, #ngold and
>relog system, double bonds count as tosingle bonds
• Determine R or S or the olloing molecule
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 31/60
Designating Con'gurationsDesignating Con'gurations
• 7andheld molecular models can be very
helpul hen arranging the molecule inspace so the loest priority group acesaay rom you
• 7ere are some other tricks that can use
– Sitching to groups on a chirality center illproduce its opposite con9guration
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 32/60
Designating Con'gurationsDesignating Con'gurations
• Sitching to groups on a chirality center ill
produce its opposite con9guration• Gou can use this trick to ad1ust a molecule so
that the loest priority group aces aayrom you
•
;ith the Eth
priority group acing aay, youcan designate the con9guration as R
• ;ork backards to sho ho the originalstructureNs con9guration is also R
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 33/60
Designating Con'gurationsDesignating Con'gurations
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 34/60
Designating Con'gurationsDesignating Con'gurations
• The R or S con9guration is used in the #K>=C
name or a molecule to distinguish it romits stereoisomer4s5
Copyright ? -.@ Aohn;iley B Sons, #nc" =ll lein, )rganic Chemistry -e@!3E
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 35/60
• $ight restricted to pass through a plane is plane- polarized
• >lane!polariHed light that passes throughsolutions o achiral compounds retains its originalplane o polariHation
• Solutions o chiral compounds rotate plane!polariHed light and the molecules are said to beoptically active
• >henomenon discovered by Aean!*aptiste *iot in
the early Oth century
Optical )cti*ityOptical )cti*ity
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 36/60
• $ight passes through a plane polariHer
• >lane polariHed light is rotated in solutions ooptically active compounds
• %easured ith polarimeter
• &otation, in degrees, is PαQ
• Clockise rotation is called de#trorotatory
• =nti!clockise is le*orotatory
Optical )cti*ityOptical )cti*ity
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 37/60
• = polarimeter measures the rotation o plane!polariHed light that has passed through a solution
• The source passes through a polari+er and thenis detected at a second polariHer
• The angle beteen the entrance and eIit planesis the optical rotation"
&easurement o Optical Rotation&easurement o Optical Rotation
O ti l ) ti itO ti l ) ti it
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 38/60
Optical )cti*ityOptical )cti*ity
• nantiomers ill rotate the plane o the light to
eual degrees but in opposite directions• The degree to hich light is rotated depends on the
sample concentration and the pathlength o thelight
•
Standard optical rotation measurements are takenith gram o compound dissolved in m$ osolution, and ith a pathlength o dm or the light
• Temperature and the avelength o light can alsoafect rotation and must be reported ithmeasurements that are taken
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 39/60
Optical )cti*ityOptical )cti*ity
• Consider the enantiomers o -!bromobutane
• R and S reer to the con9guration o thechirality center
•
4R5 and 4!5 signs reer to the direction that theplane o light is rotated
• The speci9c rotation o the enantiomer iseual in magnitude but opposite in sign
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 40/60
Optical )cti*ityOptical )cti*ity
• There is no relationship beteen the R/S con9gurationand the direction o light rotation 4R/!5
• The magnitude and direction o optical rotation can notbe predicted rom a chiral moleculeNs structure orcon9guration" #t can )$G be determined eIperimentally
• =s long as its bonds are not rearranged, its con9guration
C=)T change
• &acemic %iItures 4samples ith eual amounts o toenantiomers5 eIhibit no optical activity
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 41/60
Optical )cti*ityOptical )cti*ity
• For uneual amounts o enantiomers, the
enantiomeric e#cess , ee! can bedetermined rom the optical rotation
• For a miIture o +. 4R5 and 3. 4S5, hat
is the eeM
Copyright ? -.@ Aohn;iley B Sons, #nc" =ll lein, )rganic Chemistry -e@!E
O ti l ) ti itOptical )cti*ity
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 42/60
Optical )cti*ityOptical )cti*ity
• # the miIture has an optical rotation oRE", use the ormula to calculate the eeand the ratio o R/S
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 43/60
• %olecules ith more than one chirality center
usually have mirror image stereoisomers that areenantiomers
• #n addition they can have stereoisomeric orms
that are not mirror images, calleddiastereomers
DiastereomersDiastereomers
Stereoisomeric RelationshipsStereoisomeric Relationships
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 44/60
Stereoisomeric RelationshipsStereoisomeric Relationships
• The number o possible stereoisomers or a
compound depends on the number ochirality centers 4n5 in the compound
• ;hat is the maIimum number o possiblecholesterol isomersM
Symmetry and ChiralitySymmetry and Chirality
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 45/60
Symmetry and ChiralitySymmetry and Chirality
• =ny compound ith only ) chirality center ill be chiraland have an optical rotation
• 7oever, compounds ith an even number 4-,E,, etc"5 ochirality centers may or may not be chiral
• # a molecule has a plane o symmetry, it ill be achiral
• 7al o the molecule reJects the other hal
• #ts optical activity ill be canceled out ithin the molecule,similar to ho a pair or mirror image enantiomers cancel outeach others optical rotation
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 46/60
Symmetry and ChiralitySymmetry and Chirality
• Dra the mirror image o the cis isomer and shothat it can be superimposed on its mirror image
• *y de9nition, hen a compound is identical to itsmirror image, it is )T chiral" #t is achiral
• %olecules ith an even number o
chirality centers that have a plane osymmetry are called mesocompounds
• =nother ay to test i a compound is ameso compound is to see i it isidentical to its mirror image
Copyright ? -.@ Aohn;iley B Sons, #nc" =ll lein, )rganic Chemistry -e@!E
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 47/60
Symmetry and ChiralitySymmetry and Chirality
• #n another eIample, the plane o symmetry
identi9es it as a meso compound
• meso compounds also have less than the
predicted number o stereoisomers based on the-4n5 ormula
• Dra all our eIpected isomers and sho hoto o them are identical" = handheld modelmight be helpul
Chirality at (itrogen %hosphorus andChirality at (itrogen %hosphorus and
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 48/60
• , >, S commonly ound in organic compounds, and
can have chirality centers• Trivalent nitrogen is tetrahedral
• Does not orm a chirality center since it rapidly Jips
• #ndividual enantiomers cannot be isolated
Chirality at (itrogen %hosphorus andChirality at (itrogen %hosphorus and
SulurSulur
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 49/60
• %ay also apply to phosphorus but it Jipsmore sloly
Chirality at (itrogen %hosphorus andChirality at (itrogen %hosphorus and
SulurSulur
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 50/60
.ischer %ro/ections.ischer %ro/ections
• Fischer pro1ections can also be used to
represent molecules ith chirality centers• 7oriHontal lines represent attachments
coming out o the page
•
Uertical lines represent attachments goingback into the page
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 51/60
.ischer %ro/ections.ischer %ro/ections
• Fischer pro1ections can be used to uickly
dra molecules ith multiple chiralitycenters
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 52/60
.ischer %ro/ections.ischer %ro/ections
• Fischer pro1ections can also be used to
uickly assess stereoisomeric relationships
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 53/60
Intercon*erting EnantiomersIntercon*erting Enantiomers
• %olecules can rotate around single bonds"
•
&ecall the gauche rotational conormationo butane
• #s the gauche conormation o butanechiralM
• Dra its mirror image" #s it superimposableon its mirror imageM
• ;hy is butaneNs optical rotation eual to
HeroM• To be chiral, a compound cannot be a
rotational conormer o its mirror image
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 54/60
Intercon*erting EnantiomersIntercon*erting Enantiomers
• Compare the 4cis5!,-!dimethylcycloheIane
chair ith the 7aorth pro1ection
• The 7aorth image can be used to uicklyidentiy the compound as an achiral mesocompound"
• 7oever, a plane o symmetry can )T beound in the chair conormation
i i
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 55/60
Intercon*erting EnantiomersIntercon*erting Enantiomers
• The reely interconverting mirror images cancel out their optical rotation, soit is achiral
• This analysis is much easier to do ith a handheld models than in your mind
• # the 7aorth image has a mirror plane, then the chair ill be able tointerconvert ith its enantiomer, and it ill be achiral"
hi li% hi li
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 56/60
• = molecule that is achiral but that can become chiralby a single alteration is a prochiral molecule
%rochirality%rochirality
hi l i i i% hi l Di ti ti .
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 57/60
•
>lanar aces that can become tetrahedral are diferentrom the top or bottom
• = center at the planar ace at a carbon atom isdesignated re i the three groups in priority seuenceare clockise, and si i they are counterclockise
%rochiral Distinctions: .aces%rochiral Distinctions: .aces
% hi l Di i i .% hi l Di ti ti .
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 58/60
• =n sp3 carbon ith to groups that are the sameis a prochirality center
• The to identical groups are distinguished byconsidering either and seeing i it ereincreasedin priority in comparison ith the other
• # the center becomes R the group is pro-R and pro-S i the center becomes S
%rochiral Distinctions: .aces%rochiral Distinctions: .aces
% hi l Di ti ti i ( t% hi l Di ti ti i ( t
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 59/60
• *iological reactions oten involve makingdistinctions beteen prochiral aces or groups
• Chiral entities 4such as enHymes5 can alaysmake such a distinction
•
Iample' addition o ater to umarate
%rochiral Distinctions in (ature%rochiral Distinctions in (ature
7/23/2019 Chem 2411 Lecture 08 Stereochemistry
http://slidepdf.com/reader/full/chem-2411-lecture-08-stereochemistry 60/60
• Stereoisomers are readily distinguished bychiral receptors in nature
• >roperties o drugs depend onstereochemistry
• Think o biological recognition as euivalentto 3!point interaction
Chirality in (ature and ChiralChirality in (ature and Chiral
En*ironmentsEn*ironments