Notesale: Turn your study into money

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ORGANIC CHEM
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They are as follows:
1
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The chiral
centre usually is a Carbon atom that is bonded to four different groups
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Assign priority using the highest atomic number
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For e
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if 14N, 32S, 16O
and 12C were attached to the chiral centre, then 16S would have the
highest priority, hence it would be numbered as 1
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Direct the lowest priority group away
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The group that is placed in the back is
represented by a hash
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Of Chemistry –
University of Calgary will give an ideal representation
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Trace a path from highest (1) to lowest (4) priority
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5
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This means that if there is a double bond, it would be
considered that Carbon is bonded to two other Carbon atoms and if
there is a triple bond, Carbon is considered to be bonded to three other
Carbon atoms
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Remember that enantiomers
have opposite configuration, therefore if one molecule has S configuration,
the other has to have the R configuration and vice versa for them to be
enantiomers
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Remember that the one of lowest priority (lowest atomic
number) should be on the hash, which would mean it is in the back
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Hydrogen has the lowest atomic # hence it should be on the hash
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When rotating the groups, one group is ‘held steady,’
meaning that this group is unaffected during the rotation and will
remain in the same position at the end
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2

THE PAIR IN a) IS AN ENANTIOMER

b) The first pair does not have to be rotated because the group with the
lowest priority (Hydrogen) is in the back
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3

THE PAIR IN b) IS NOT AN ENANTIOMER

N
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: If there is an instance where the group with the lowest priority is
not in the plane but on the wedge, (look back at the diagram in the rules
section) then all you have to do is find the configuration and write the
opposite, instead of rotating
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g
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5

Here are a few practice questions:

6

Here are some websites that you can go and get some practice:
http://www
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com/STchiralcentersRS
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colby
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html
http://www
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edu/chemistry/OChem/STEREOCHEM/chframe9
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colby
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html
http://www
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edu/chemistry/OChem/STEREOCHEM/exframe1
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colby
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html

Answer: All the molecules are in the R configuration

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