Chemistry Reference
In-Depth Information
c.
The aromatic units in (-)-ephedrine and (-)-epinephrine are slightly different
and (-)-epinephrine lacks the C-2 stereogenic center present in (-)-
ephedrine. They both have the same configuration at C-1.
5.55
For kavain, the R configuration is:
OCH
3
3
4
H
R
O
O
2
1
and the group priorities are noted as 1, 2, 3, and 4.
5.56
The reaction of (
R
)-2-chlorobutane with chlorine to give 2,3-dichlorobutane involves
initial conversion to an intermediate free radical (consult Sec. 2.13). This free radical
can react with chlorine molecules from the “top face” to give
meso
-2,3-
dichlorobutane, or the “bottom face” to give (2
R
,3
R
)-dichlorobutane.
H
H
Cl
H
H
3
(
R
-2-chlorobutane
C
CH
3
Cl
Cl
H
H
H
H
Cl
Cl
H
3
C
Cl
Cl
2
top
face
Cl
2
bottom
face
H
H
H
3
meso
-2,3-ichlorobutane
C
H
3
C
CH
3
CH
3
CH
3
Cl
free radical
(2 ,3 )-2,3-dichlorobutane
RR
The two faces of the free radical are clearly different because their reactions with
chlorine give different products. Since the faces of the radical differ, the steric
environments must differ and the reaction rates will differ. This will lead to formation
of an unequal ratio of the two diastereomeric products.
5.57
The receptor site for (+)-carvone and (-)-carvone must be chiral such that the
complex of the (+) and (-) isomers with the receptor are diastereomers. Therefore
(+)-carvone and (-)-carvone have different odors.
5.58
a.
In this reaction, a
chiral
product is formed from
achiral
reactants, so both
enantiomers (of 1-phenylethanol) will be formed in equal amounts (see
Sec. 5.11).
b.
In this reaction, a compound with one stereogenic center is converted to a
compound with two stereogenic centers. The new stereogenic center can be
either
R
or
S
and the latter is a
meso
compound.
