EXAM 2 - CHEM 5821 – OCTOBER 23, 2014 – NAME _________________________
1. (16 pts.) Assign the absolute stereochemistry [(R) or (S)] of all 8 chiral centers in Citrinadin B [J.
Org. Chem. 2005, 70, 9430.].
OH
O
21
18
3
9
N
O
H
O
N
H
O
14
16
N
'
2
12
O
N
H
CH3
21.
3.
9.
18.
16.
12.
14.
2'.
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EXAM 2 - CHEM 5821 – OCTOBER 23, 2014 – NAME _________________________
2. Some A values: i-Pr = 2.1 kcal/mole; Me = 1.8 kcal/mole, Cl = 0.52 kcal/mole
A) (6 pts.) Draw the structure of (1S,2S,4R)-2-chloro-1-isopropyl-4-methylcyclohexane. Use wedges and
dashes to clearly indicate stereochemistry.
B) (8 pts.) Draw both chair forms of (1S,2S,4R)-2-chloro-1-isopropyl-4-methylcyclohexane. Do not use
wedges and dashes when drawing chairs.
C) (5 pts.) Draw the MAJOR E2 product obtained from dehydrohalogenation of (1S,2S,4R)-2-chloro-1isopropyl-4-methylcyclohexane. Use wedges and dashes to clearly indicate stereochemistry.
D) (5 pts.) Which of the 2 chairs from part B) is the most stable.
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EXAM 2 - CHEM 5821 – OCTOBER 23, 2014 – NAME _________________________
3. (20 pts.) Nitriles can be converted into carboxylic acids by hydrolysis under acidic conditions (path a); or
under basic conditions (path b) followed by an acidic workup. Propose stepwise reaction mechanisms
for both pathways. Draw the structures of all of the intermediates formed in each reaction pathway
(including resonance structures). Use arrows to show “pushing” of electrons.
R C N
a) HCl, H2O, heat
or
RCO2H
b) NaOH, H2O, heat,
followed by H3O+
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EXAM 2 - CHEM 5821 – OCTOBER 23, 2014 – NAME _________________________
4. A.) (4 pts) Draw the structure of (3S,4S)-3-chloro-3,4-dimethylheptane. Use wedges and dashes to
clearly indicate stereochemistry.
B.) (6 pts) Draw a complete set of Newman Projections for rotation about the C3-C4 bond in (3S,4S)-3chloro-3,4-dimethylheptane. Use the abbreviations Me, Et, and Pr for any alkyl groups in your Newman
Projections. Make sure C3 is the front carbon.
C.) (5 pts) Draw the structure(s) of the major SN1 product(s) obtained from reaction of (3S,4S)-3-chloro-3,4dimethylheptane with water (H2O). Use wedges and dashes to clearly indicate stereochemistry.
C.) (5 pts) Draw the structure of the major E2 product obtained from dehydrohalogenation of (3S,4S)-3chloro-3,4-dimethylheptane.
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EXAM 2 - CHEM 5821 – OCTOBER 23, 2014 – NAME _________________________
5. (20 pts) Draw the structures of the major organic products formed after each step (where applicable) in
the following reactions. Include product stereochemistry (where applicable). Indicate racemic mixtures with
the () symbol.
A)
CH3
1) 4-NO2C6H4CO2H
EtO2CN=NCO2Et, PPh3
B)
OH
C)
Hg(OAc)2, H2O
OH
2) KOH, MeOH, reflux
1) Na2Cr2O7, H2SO4,
acetone-water
2) CH2N2
1) H B
, THF
D)
2) H2O2, NaOH, H2O
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