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CHM 136 H
Stereochemistry
Chapter 5 excluding 5.3, 5.4, 5.10, 5.12
Chapter 25: 25.2 only
McMurry, 9th edition
1
Chapter 7: 7.4, 7.5
Isomers
Different compounds with the same molecular formula
Constitutional isomers:
isomers with different
atomic connectivities
Stereoisomers: isomers
with the same atomic
connectivity but with
different geometries
O
OH
H
Br
H
Br
H
Br
Br
H
2
1
2
McMurry 9th Ed., Section 7.5
Di-substituted alkenes can be named cis or trans:
Cahn-Ingold-Prelog rules for naming alkenes
First, a brief look at alkene stereochemistry
cis trans
We need rules for naming
tri- and tetra-substituted alkenes
3
Tri- and tetra-substituted alkenes
Two stereoisomers:
Z: the two groups of higher priority are on
the same side of the double bond
E: the two groups of higher priority are on
the opposite side of the double bond
We determine priority with the Cahn-Ingold-Prelog rules
4
3
4
The Cahn-Ingold-Prelog rules
1. Rank atoms on each end of the double
bond in decreasing atomic number
Br > Cl > F > O > N > C … > H
2. If the first atoms in the substituent are the
same, look at the 2nd, the 3rd, the 4th, ….,
until the first difference is found
