Chapter 5 Stereochemistry The Arrangement of Atoms in Space; The Stereochemistry of Addition...
-
Upload
chastity-sullivan -
Category
Documents
-
view
239 -
download
0
Transcript of Chapter 5 Stereochemistry The Arrangement of Atoms in Space; The Stereochemistry of Addition...
Chapter 5
Stereochemistry
The Arrangement of Atoms in Space;
The Stereochemistry of Addition Reactions
Molecular Chirality: Molecular Chirality: EnantiomersEnantiomers
A molecule is A molecule is chiralchiral if its two mirror image if its two mirror image forms forms are not are not superimposable upon one superimposable upon one another. another.
A molecule is A molecule is achiralachiral if its two mirror if its two mirror image image forms forms areare superimposable. superimposable.
ChiralityChirality
BrBrClCl
HH
FF
Bromochlorofluoromethane is chiralBromochlorofluoromethane is chiral
It cannot be It cannot be superimposed point superimposed point for point on its mirror for point on its mirror image.image.
BrBrClCl
HH
FF
Bromochlorofluoromethane is chiralBromochlorofluoromethane is chiral
HH
ClClBrBr
FFTo show To show nonimsuperposability, nonimsuperposability, rotate this model 180° rotate this model 180° around a vertical axis.around a vertical axis.
Chirality & nonsuperimposable mirror images Chirality & nonsuperimposable mirror images
EnantiomersEnantiomers
QuickTime™ and aSorenson Video decompressorare needed to see this picture.
IsomersIsomers
stereoisomersstereoisomersconstitutionalconstitutionalisomersisomers
IsomersIsomers
stereoisomersstereoisomersconstitutionalconstitutionalisomersisomers
diastereomersdiastereomersenantiomersenantiomers
Physical Properties of Physical Properties of EnantiomersEnantiomers
Physical properties are the same:Physical properties are the same: melting point, boiling point, density, etcmelting point, boiling point, density, etc
Some others are differentSome others are different: : properties that depend on the shape of molecule properties that depend on the shape of molecule
eg. biological-physiological and optical properties. eg. biological-physiological and optical properties.
Properties of enantiomersProperties of enantiomers
OO OO
CHCH33 CHCH33
HH33CC HH33CCCHCH22 CHCH22
OdorOdor
(–)-Carvone(–)-Carvonespearmint oilspearmint oil
(+)-Carvone(+)-Carvonecaraway seed oilcaraway seed oil
IbuprofenIbuprofen is chiral, but normally sold as is chiral, but normally sold as
a racemic mixture. The enantiomer belowa racemic mixture. The enantiomer below
is the one responsible for its analgesic is the one responsible for its analgesic
and antiinflammatory properties.and antiinflammatory properties.
Chiral drugsChiral drugs
CHCH22CH(CHCH(CH33))22
HHHH33CC
CC
OO
CC
HOHO
A Sedative or a Potent Teratogen?
a carbon atom with foura carbon atom with fourdifferent groups attached to itdifferent groups attached to it
also called:also called:chiral center; chiral carbonchiral center; chiral carbonasymmetric centerasymmetric centerasymmetric carbonasymmetric carbonstereocenterstereocenterstereogenic centerstereogenic center
The chiral carbon atomThe chiral carbon atom
ww
xx yy
zz
CC
A molecule with a single stereogenic A molecule with a single stereogenic center is chiral.center is chiral.
2-Butanol is an example.2-Butanol is an example.
Chirality and chiral carbonsChirality and chiral carbons
CHCH33
OHOH
HH
CC CHCH22CHCH33
Examples of molecules with 1 chiral carbonExamples of molecules with 1 chiral carbon
CHCH33
CC
CHCH22CHCH33
CHCH22CHCH22CHCH22CHCH33CHCH33CHCH22CHCH22
a chiral alkanea chiral alkane
Examples of molecules with 1 chiral carbonExamples of molecules with 1 chiral carbon
Linalool, a naturally occurring chiral alcoholLinalool, a naturally occurring chiral alcohol
OHOH
Examples of molecules with 1 chiral carbonExamples of molecules with 1 chiral carbon
1,2-Epoxypropane: a chiral carbon1,2-Epoxypropane: a chiral carboncan be part of a ringcan be part of a ring
OO
HH22CC CHCHCHCH33
attached to the chiral carbon are:attached to the chiral carbon are:
——HH
——CHCH33
——OCHOCH22
——CHCH22OO
Examples of molecules with 1 chiral carbonExamples of molecules with 1 chiral carbon
Limonene: a chiral Limonene: a chiral carbon can be part of a carbon can be part of a ringring
CHCH33
HH CC
CHCH33
CHCH22
attached to theattached to thechiral carbon are:chiral carbon are:
——HH
——CHCH22CHCH22
——CHCH22CH=CH=
——C=C=
Examples of molecules with 1 chiral carbonExamples of molecules with 1 chiral carbon
Chiral as a result of isotopic substitutionChiral as a result of isotopic substitution
CHCH33CCDD
TT
HH
A molecule with a single chiral carbonA molecule with a single chiral carbonmust be chiral.must be chiral.
But, a molecule with two or more But, a molecule with two or more
chiral carbons may be chiralchiral carbons may be chiral
or it may not. or it may not.
We’ll return to this when we consider molecules We’ll return to this when we consider molecules with more than one chiral carbon atom.with more than one chiral carbon atom.