Download t.h.e_2 - Homework Market

Question #1
Rank the following alkenes in order of MOST to LEAST exothermic upon catalytic
hydrogenation of each to its corresponding alkane.
H2
Alkene
Alkane + HEAT
Pd-C
Provide a brief explanation that describes why the reactions are ordered as observed. What is the
major stabilizing effect that determines the stability order in this series? HINT: you’ll likely
want to draw the structure of each before you proceed.
(a) cis-2-hexene
(b) 1-hexene
(c) 2,3-dimethyl-2-butene
(d) 2-methyl-2-pentene
(e) trans-2-hexene
energy
relative
enegy of
product
(a)
(b)
(c)
(d)
(e)
Question #2
The following sets of question pertain to intermolecular forces:
(a) Provide a valid structure for each of the following molecules and then, arrange the
compounds in order of increasing boiling point (you may want to consult the Aldrich
catalog, an MSDS, or go to chemfinder.com to find the bps). Briefly explain your
ordering being sure to indicate the type and relative magnitude of intermolecular
interactions (e.g. VDW interactions, dipole-dipole, and hydrogen bonding) that exist in
each case.
1.
2.
3.
4.
5.
6.
7.
dichloroethanoic acid (dichloroacetic acid)
2-methoxybutane
ethyl 3-oxobutanoate (ethylacetoacetate)
n-heptane
3,3-dimethyl-2-pentanol
3-amino-1,2-propanediol
ethene (ethylene)
(b) Predict which of the following salts is likely to have unusually high solubility in a (nonaqueous) hydrocarbon solvent. Briefly explain your choice.
C4H9
vs.
NH4 Cl
C4H9
N
Br
(CH2)15CH3
C4H9
(c) Normally, the drug shown below is much more soluble in lipid-like solvents (e.g.
benzene) than it is in water. However, its water solubility INCREASES considerably
when the aqueous solution contains moderate amounts of strong acid (e.g. in the
stomach) as shown by the reaction below. Explain the solubility differences.
H
H
O
+
soluble in benzene
O
O
H
H
+
H2O
Question #3
The following compound was recently reported in the Journal of Medicinal Chemistry as a key
synthetic intermediate in the synthesis of a potent plant-derived natural product used in the
treatment of cancer.
H
Ph
OCH3
H
HO H CH
3
Conformational Interaction
1,3-diaxial (OH and H)
1,3-diaxial (OCH3 and H)
1,3-diaxial (CH3 and t-butyl)
1,3-diaxial (OCH3 and CH3)
1,3-diaxial (OCH3 and OH)
1,3-diaxial (Ph and H)
1,3-diaxial (Ph and t-butyl)
1,3-diaxial (Ph and CH3)
1,3-diaxial (Ph and OH)
1,3-diaxial (H and C(CH3)3)
1,3-diaxial (H and CH3)
Gauche (t-butyl and OH)
Gauche (t-butyl and CH3)
Gauche (OH and CH3)
H (kcal/mol)
1.3
1.7
3.8
2.3
2.4
1.9
4.1
3.2
3.5
2.7
0.9
2.7
2.3
1.8
(a) Name the structure shown above WITH assignment of R/S configuration for each
stereogenic atom.
(b) Draw the two chair conformations (using the templates provided) of the structure above.
Be sure to LIST all destabilizing interactions and provide a value for total potential
energy (E) for each conformation (more stable and less stable).
more stable
E=
less stable
E=
(c) Find the potential energy difference (H) between the two possible conformations and
use this value to determine the equilibrium constant (Keq) at 25oC for the chair flip from
the MORE stable to the LESS stable conformation. Do your values for H and Keq
make sense? (Assume H  G)
Question #4
For the following pairs of molecules, assign the absolute configuration (R or S) to each
stereogenic carbon and indicate the stereochemical relationship (identical, enantiomers,
diastereomers, constitutional isomers, or meso compound) between the two molecules in each
pair.
Pair #1
H
CH3
H3C
H
Pair #2
H
Cl
H3C
Cl
HO
OH
CH3
H
Pair #3
OCH3
Br
H3CO
Br
Pair #4
H3C
H3C
Br
Br
Pair #5
OH
H
CH3
HO
HO
OH
H
CH3
Question #5
Mirror Images Pharmaceutical Corporation has designed a novel neuromuscular blocking agent
and wants to submit the molecule shown below for patent approval. You are the lead organic
chemist on the legal team and have been asked to investigate certain aspects of stereochemistry in
order to submit a report along with the patent application. Your report requires the following
information:
H
O
H
H
O
H
Br
CH3
OCH3
OCH3
CH3
Br
(a) Identify all stereocenters that are not asymmetric carbons in the molecule on the
RIGHT--- label with an SC
(b) Identify all asymmetric carbons in the molecule on the LEFT--- label with an AC
(c) Assign the configuration about all stereocenters and asymmetric carbons on BOTH
molecules --- use E/Z or R/S assignments
(d) Provide the complete IUPAC name for the compound on the LEFT --- identify the
longest chain and any priority groups
(e) Show all polar covalent bonds by writing in the dipole arrow for the molecule on the
RIGHT
(f) Identify the stereochemical relationship between the two molecules (identical,
enantiomers, diastereomers, constitutional isomers, or meso)