Chemistry Reference
In-Depth Information
F
Cl
Br
H
(
E
-1-bromo-2-chloro-1-fluoroethene
5.13
a.
The priorities are CH
2
=C
−
> H and CH
3
CH
2
−
> H. The two highest-priority
groups, CH
2
=CH
−
and CH
3
CH
2
−
, are
entgegen
(opposite).
b.
The two highest-priority groups, CH
3
and CH
3
, are
zusammen
, or together.
H
3
C
CH
3
H
(
Z
)-2-butene
H
s
5.14
+0.66
α
20
D
44
o
(ethanol)
=
=
1.5
50
0.5 x
5.15
5.16
There are several ways to approach this problem. Here's one. Assign priorities to the
four groups.
4
H
1
2
CH
3
CH
2
CH
3
OH
1
If the lowest priority group is in a vertical position, determine whether the sequence
of the remaining three groups (1
→
2
→
3) is clockwise (
R
) or counterclockwise (
S
). In
this case, it is clockwise and the Fischer projection represents (
S
)-2-butanol.
