Assignment
Question #1
Rank the following alkenes in order of MOST to LEAST exothermic upon catalytic hydrogenation of each to its corresponding alkane.
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
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. dichloroethanoic acid (dichloroacetic acid)
2. 2-methoxybutane
3. ethyl 3-oxobutanoate (ethylacetoacetate)
4. n-heptane
5. 3,3-dimethyl-2-pentanol
6. 3-amino-1,2-propanediol
7. ethene (ethylene)
(b) Predict which of the following salts is likely to have unusually high solubility in a (non-aqueous) hydrocarbon solvent. Briefly explain your choice.
(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.
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.
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Conformational Interaction
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ΔH (kcal/mol)
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1,3-diaxial (OH and H)
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1.3
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1,3-diaxial (OCH3 and H)
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1.7
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1,3-diaxial (CH3 and t-butyl)
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3.8
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1,3-diaxial (OCH3 and CH3)
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2.3
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1,3-diaxial (OCH3 and OH)
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2.4
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1,3-diaxial (Ph and H)
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1.9
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1,3-diaxial (Ph and t-butyl)
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4.1
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1,3-diaxial (Ph and CH3)
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3.2
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1,3-diaxial (Ph and OH)
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3.5
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1,3-diaxial (H and C(CH3)3)
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2.7
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1,3-diaxial (H and CH3)
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0.9
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Gauche (t-butyl and OH)
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2.7
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Gauche (t-butyl and CH3)
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2.3
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Gauche (OH and CH3)
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1.8
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(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).
(c) Find the potential energy difference (ΔH) 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 ΔH ≈ ΔG)
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.
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:
(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).
Attachment:- Chemistry-Assignment.rar