Download Organic Chemistry 102 Problems #4 Solutions Due Friday, Feb. 9

Organic Chemistry 102
1.
Problems #4
Solutions
Due Friday, Feb. 9
Give the proper name or structure for each of the following. Name and show any stereochemistry present in these.
names:
OH
b)
c)
a)
OH
CH3
HO
2,4-diethyl-1-heptanol
1R,6S(cis)-6-methylcyclohex-3-en-1-ol
structures:
d) trans-cyclohexene glycol
H
exo-bicyclo[2.1.1]hex-2-en-5-ol
OH
e) pentamethylene glycol
HO
OH
OH
2.
a)
For each set of experimental facts presented below, give reasonable explanations for the observed trends, using the
relationships between structure and physical properties.
CH3
CH3CH2CH2CH2OH
CH3 CH2 CH CH3
Each of the alcohols can hydrogen
bond with the water to help it
OH
dissolve. The more polar of the
solubility
infinitely soluble
8.3g/100 mL H2O
26.0g/100 mL H2O
in water
in H2O
Explain
three is 1-butanol, which would
} each
seem to indicate it should be the
separately
boiling
118°C
99.5°C
82.5°C
one that is most soluble in water.
point
Therefore there must be another
explanation. The intermolecular interactions between the 2° and 3° alcohols are less due to
smaller surface areas and poorer intermolecular hydrogen bonding. This makes it easier for the
water molecules to separate the alcohols. The other reason is that the 2° and 3° alcohols are more
compact and disrupt the water molecules less.
Boiling Point:
This is just what one would expect based on intermolecular interactions. The 1°
alcohol would have more effective H-bonding, as well as more effective London Dispersion
forces (more surface area). We learned earlier that branching reduces boiling point due to a
reduction in the dispersion forces. But also here, the hydrogen bonding is made less effective
with an increase in the steric size of the alkyl group near the oxygen.
H3C
C
CH3
OH
b)
CH3CH2CH2CH2OH
CH3CH2CH2CH2CH2CH2OH
CH3 CH2
H
C
H
C CH2 CH3
OH OH
solubility
in water
boiling
point
8.3 g/100mL H2O
118°C
0.59 g/100mL H2O
157°C
infinitely soluble
in H2O
207°C
}
Explain
each
separately
Solubility: the
number of hydroxyl
groups will increase
the solubility in water
due to increased Hbonding interactions.
Butanol has fewer
non-polar methylene
groups than hexanol making it more soluble.
Boiling point: both butanol and hexanol are primary alcohols but hexanol has a higher molecular weight,
therefore increasing intermolecular London forces and the boiling point. The hexanediol, with
the two OH groups, has extra intermolecular interactions, including additional H-bonding, which
will raise the boiling point.
3.
Provide two different syntheses, using structurally different starting materials, for the following compounds where a
Grignard reagent is used in each method.
1. BrMgCH2CH2CH3/ether
CH3CH2CH2 CH
a)
or
H
2. H+/H2O
CH3CH2CH2 CH CH2CH2CH3
O
C OCH2CH3
1. 2 BrMgCH2CH2CH3/ether
O
2. H+/H2O
OH
O
1. BrMg-CH(CH3)2/ether
b)
2. H3O+
H
O
CH3
OH
MgBr
C
H
/ether
1.
or
2. H3O+
CH3
H
BrMg
CH2CH3
c)
H3C
O
C
O
H3C
H3O+
2.
or
H3C
4.
C
1.
CH2CH3
C
OH
CH2CH3
1. BrMgCH3
C
2. H3O+
O
1. BrMgCH2CH3
2. H3O+
Provide reagents and conditions to carry out the following transformations. If more than one method is possible,
choose the one that is most commonly used for that transformation.
H
H2
C
PCC/CH2Cl2
OH
O
a)
OH
O
H2CrO4/H2SO4
b)
"
acetone
O
OH
H2CrO4/H2SO4
c)
acetone
CH3
CH3
1. OsO4
d)
OH
2. NaHSO3/H2O
OH
OH
H2
C
1. LiAlH4/ether
O
e)
O
NaBH4/EtOH
"
f)
O
H
NaBH4/EtOH
g)
HO
OH
2. NaOH/H2O
H
O
+ enantiomer (1:1)
O
HO
H2
C
OH
5.
Predict the major organic products expected in the following reactions. Pay particular attention to stereochemistry in
your answers. When mixtures are expected, indicate the relative amounts of each.
H3 C
OH
H3 C
CH3
a)
HBr
H3C
Br
H3 C
CH3
HCl/ZnCl2
b)
OH
H3C
c)
Cl
H3C
CH3
Br
HBr
H3C
+
H3 C
OH
H3C
H3 C
d)
Br
H3C
CH3
PBr3
"
H3 C
Br
H3C
1. Ts-Cl/py
H3 C
e)
H3 C
OH
CH3
f) H C
3
H
CH2
2. KO(t-Bu)/HO(t-Bu) H3C
1. Ts-Cl/py
CH3
H3 C
2. NaI/acetone
I
OH
H
H3C
H3 C
g)
CH3
H3C
1. BH3:THF
2. H2O2/NaOH
CH3
H3C
OH
h)
+ enantiomer (1:1)
H3 C
OH
H3 C
CH3
1. Hg(OAc)2/THF/H2O
"
2. NaBH4/NaOH