Transcript Slide 1

© www.chemsheets.co.uk
AS 053
12-Jul-12
GEOMETRIC ISOMERISM
CH3
X
C
H
H
C
CH3
CANNOT ROTATE AROUND C=C
© www.chemsheets.co.uk
AS 053
12-Jul-12
GEOMETRIC ISOMERISM
CH3
H
C
CH3
C
H
CH3
C
CH3
(E) but-2-ene
E entgegen (opposite)
H
C
H
(Z) but-2-ene
Z zusammen (together)
© www.chemsheets.co.uk
AS 053
12-Jul-12
GEOMETRIC ISOMERISM
PRIORITY: H < CH3 < CH2CH3
Look at atomic numbers of atoms attached to C=C (or
subsequent atoms if the same).
Highest values opposite = E
Highest values together = Z
9
F
CH3
C
6
12
CH3
6
12
1
6, 612
CH2CH3 12,
H
C
C
Br
35
E 2-bromo-3-fluorobut-2-ene
12
6
C
CH3
CH3
12
6
E 3-methylpent-2-ene
© www.chemsheets.co.uk
AS 053
12-Jul-12
GEOMETRIC ISOMERISM
CH3
H
C
CH3
C
H
CH3
C
CH3
C
H
H
trans but-2-ene
cis but-2-ene
(E) but-2-ene
(Z) but-2-ene
BOTH C ATOMS OF C=C MUST HAVE
TWO DIFFERENT GROUPS
© www.chemsheets.co.uk
AS 053
12-Jul-12
TASK
CH3
H
C
NO
C
CH3
H
methylpropene
H
H
C
CH3
H
C
C
Z
Cl
Cl
CH3
YES
C
E
H
1-chloropropene
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AS 053
12-Jul-12
TASK
CH2
CH3
C
CH3
NO
C
H
CH3
2-methylpent-2-ene
H
CH2
C
H
CH2
CH3
NO
C
CH2
CH3
2-ethylpent-1-ene
© www.chemsheets.co.uk
AS 053
12-Jul-12
TASK
CH3
CH3
C
C
E
H
CH3
H
CH2
CH3
CH3
YES
C
C
Z
CH2
CH3
3-methylpent-2-ene
H
H
C
H
NO
C
CH2
CH3
but-1-ene
© www.chemsheets.co.uk
AS 053
12-Jul-12
TASK
CH3
CH3
C
CH3
CH2
CH3
C
Z
CH2
C
CH2
CH3
CH3
CH2
CH3
YES
C
E CH3
3,4-dimethylhex-3-ene
CH3
CH3
CH3
Cl
YES
C
Br
C
C
Z
Cl
Br
C
E
CH3
2-bromo-3-chlorobut-2-ene
© www.chemsheets.co.uk
AS 053
12-Jul-12