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Stereochemistry

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Chapter 5 Stereochemistry The Arrangement of Atoms in Space; The Stereochemistry of Addition Reactions Molecular Chirality: Enantiomers Chirality A molecule is chiral ... – PowerPoint PPT presentation

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Title: Stereochemistry


1
Chapter 5 Stereochemistry The Arrangement of
Atoms in Space The Stereochemistry of Addition
Reactions
2
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3
Molecular Chirality Enantiomers
4
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5
Chirality
  • A molecule is chiral if its two mirror image
    forms are not superimposable upon one another.
  • A molecule is achiral if its two mirror image
    forms are superimposable.

6
Bromochlorofluoromethane is chiral
  • It cannot be superimposed point for point on its
    mirror image.

Cl
Br
H
F
7
Bromochlorofluoromethane is chiral
Cl
Cl
Br
Br
H
H
F
F
  • To show nonimsuperposability, rotate this model
    180 around a vertical axis.

8
Enantiomers
Chirality nonsuperimposable mirror images
9
Isomers
constitutional isomers
stereoisomers
10
Isomers
constitutional isomers
stereoisomers
enantiomers
diastereomers
11
Physical Properties of Enantiomers
12
Properties of enantiomers
  • Physical properties are the same melting
    point, boiling point, density, etc
  • Some others are different properties that
    depend on the shape of molecule eg.
    biological-physiological and optical properties.

13
Odor
CH3
CH3
O
O
H3C
H3C
CH2
CH2
()-Carvonespearmint oil
()-Carvonecaraway seed oil
14
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15
Chiral drugs
  • Ibuprofen is chiral, but normally sold asa
    racemic mixture. The enantiomer belowis the one
    responsible for its analgesic and
    antiinflammatory properties.

16
A Sedative or a Potent Teratogen?
17
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18
The chiral carbon atom
  • a carbon atom with fourdifferent groups attached
    to it
  • also called
  • chiral center chiral carbonasymmetric center
  • asymmetric carbonstereocenter
  • stereogenic center

19
Chirality and chiral carbons
  • A molecule with a single stereogenic center is
    chiral.
  • 2-Butanol is an example.

H
CH3
CH2CH3
OH
20
Examples of molecules with 1 chiral carbon
a chiral alkane
21
Examples of molecules with 1 chiral carbon
Linalool, a naturally occurring chiral alcohol
22
Examples of molecules with 1 chiral carbon
1,2-Epoxypropane a chiral carbon can be part of
a ring
  • attached to the chiral carbon are
  • H
  • CH3
  • OCH2
  • CH2O

23
Examples of molecules with 1 chiral carbon
Limonene a chiral carbon can be part of a ring
  • attached to thechiral carbon are
  • H
  • CH2CH2
  • CH2CH
  • C

24
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25
Examples of molecules with 1 chiral carbon
Chiral as a result of isotopic substitution
26
A molecule with a single chiral carbonmust be
chiral.
  • But, a molecule with two or more chiral carbons
    may be chiral or it may not.
  • Well return to this when we consider molecules
  • with more than one chiral carbon atom.
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