Download Enantiomers and Diastereomers File

Structural, Geometric, Enantiomer
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Compounds that have the same molecular
formula but difference structure and different
properties
3 types:
 Structural isomers
 Geometric isomers
 Enantiomers
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same KIND and AMOUNT of atoms
(molecular formula) but the atoms have
different connectivity
Structural isomers usually have different
physical and chemical properties
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How many different
structures can you
make from C5H12?
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SAME molecular formula and the SAME
connectivity but different spatial
arrangements
Due to inflexibility of a bond, usually either:
 double bonds (cis and trans formation)
 bonds that can’t rotate (i.e. in a ring formation)
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Why is example 1 not a pair of geometric
isomers?
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Hint: Look at example 2 & 3 and compare to example 1.
What is the minimum requirement for a pair of molecules to
be considered geometric isomers?
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Answer: Each carbon of the double bond
must have two different substituent groups
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So if example 1 is not a pair of geometric
isomers, what are they classified as?
Another type of geometric isomer is found in ring
structures and doesn’t involve double bonds
 Due to the inflexible nature of the bonds that make
up the ring
 Note: The ring lies on a flat plane (e.g. your paper)
and the OH groups are perpendicular to the plane
(e.g. up and down)
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Molecules that are
mirror images of each
other
Note: left and right
hands are a pair of
enantiomers (mirror
images not identical)
What other body parts
that are enantiomers?
Activity:
 Build these molecule
pairs
 Compare them to
determine whether
they are enantiomers
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How are the lower
pairs of molecules
different from the
upper pairs?
What condition do
you think is
necessary for a pair
of molecules to be
enantiomers?
X
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Requirement: Enantiomers can only occur
when each of the four groups attached to the
central carbon atom are all different.
The central carbon is known as a chiral
carbon and the molecule is chiral.
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Asymmetric carbon: carbon with 4 different
groups bonded to it
No plane of symmetry
Mirror image is non-superimposable
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lacks chiral properties
has a plane of symmetry
Double bond to
carbon = achiral
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Amino acids are building
blocks of proteins
Some amino acids can
exist as enantiomers
because of their chiralty
Switching an enantiomer
in a biological system can
have detrimental effects
Enzymes are always chiral.
Their binding sites are in a specific orientation that
fits only one form of an enantiomer.
 Binding sites won’t fit if the wrong enantiomer is
present.
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A mixture that contains equal quantities of
both enantiomers
Enantiomers can interconvert in vivo
Story of thalidomide (1960’s)
 A racemic drug given to
pregnant women to combat
morning sickness
 One of the enantiomers
caused birth defects
(teratogen) and death
http://www.thalidomide.ca/the-canadian-tragedy/
What’s in Advil (ibuprofen)?
 Production results in a racemic mixture
 One of the enantiomers is effective as an
anti-inflammatory
 Takes about 30 minutes for the inactive
enantiomer to be converted
http://www.brookscole.com/chemistry_d/templates/student_resources/0534389996_mcmurry/CHEM_A_WORK/chapter9.htm
The World of Chemistry, 4 ed. 2007. Thomson Brooks/Cole. Joesten, Castellion, & Hogg.
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Do the molecules have the same
chemical formula?
 If the formula is different, they are NOT
isomers but completely different molecules
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Are the molecules identical?
 If they are, they are NOT isomers.
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Are all the atoms connected in the same
way to other atoms?
 If not, they are STRUCTURAL isomers
Look for an inflexible bond (double bond
or ring) for geometric isomers
 Look for mirror images for enantiomers
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http://2.bp.blogspot.com/_K91FA3B4cpM/SJ_NUmBWWGI/AAAAAAAAACY/UzL8H8Q4oag/s400/ist2_1744503_frustration.jpg
Isomer
Structural
Geometric
Enantiomer
Same
Different
Requirements
Isomer
Same
Different
Structural
Molecular
formula
Connectivity
Geometric
Enantiomer
Requirements
Isomer
Same
Different
Structural
Molecular
formula
Connectivity
Geometric
Molecular
formula &
connectivity
Enantiomer
Spatial
arrangement
Requirements
Double bond
Different substituent
groups on each carbon
Isomer
Same
Different
Requirements
Structural
Molecular
formula
Connectivity
Geometric
Molecular
formula &
connectivity
Spatial
arrangement
Double bond
Different substituent
groups on each carbon
Molecular
Enantiomer formula &
connectivity
Spatial
arrangement
Chiral molecules
Mirror image
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structural isomers
structural isomers
geometric
isomers
structural isomers
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geometric
isomers
structural isomers
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