KEY
Massachusetts Institute of Technology
Organic Chemistry 5.13
Wednesday, October 25, 2006
Prof. Timothy F. Jamison
Hour Exam #2
Name
_____________________________________________
(Please both print and sign your name)
Official Recitation Instructor
_________________________________
Directions:
Closed book exam, no books, notebooks, notes, etc. allowed.
Calculators are not permitted for the exam. However, rulers, and molecular
model sets are permitted.
Please read through the entire exam before beginning, in order to make sure
that you have all the pages and in order to gauge the relative difficulty of each
question. Budget your time accordingly.
Show all your work if you wish to receive partial credit. You should have 8
pages total: 6 exam pages including this page and 2 blank pages for
scratchwork.
Question:
1. _________/
2. _________/
3. _________/
4. _________/
Total: __________/
Grader:
14 points (page 2)
16 points (page 3)
48 points
22 points
_________
_________
_________
100 points
_________
1
1. (30 points total, 2 points per box) In each box below, draw the structure of the major
product of the reaction. Indicate relative stereochemistry where appropriate. If no reaction
occurs, put a large X in the box. (Note: “D” = deuterium, 2H)
D
a.
O
H3C
H
+
H
CH3
O
D
D
O
Me
∆
Me
O
D
b.
O
H3C
CH3
+ H3CO
Me
Me
CO2Me
∆
CH3
Me
d.
Me
(CH3)2S
c.
CH3
O3
O
H
O
CHO
Me
O
O
e.
Me
NaBH4
OH
OH
f.
(R)
HO
Me
H
H+
EtOH
O H
(S)
CH3
g.
BF3
MgBr
OH
Ph
H
(S) Me
OE+
Figure by MIT OCW.
2
(1., continued – see previous page for directions)
h.
O CH3
H3C
O
CH3
CH3
H3C
CH3 1. PhCH2OH,
Hg(OAc)2
O
Me
O
Ph
Me
2. NaBH4
CH3
H
i.
Me
CH3
O
Ph
j.
Me
O
CH3
N
Me
∆
Ph
H
or
m.
H H
o.
SH
Br
H H
Π2S + Π2S
(or (IS, cis)
NaOH
S Na
Me
hν
HH
Must have "x"
in box
n. No Reaction
Me
Me
H
l.
[3,3]
COPE
O
Me
CH3
∆
Me
∆
Me
H
k.
C
C=N=O
1.NaOH
2. excess
EtBr
S Br
∆
H3C
Figure by MIT OCW.
3
2. (48 points total)
a. Draw the orbitals (by shading the lobes appropriately) at each energy level for
1,3,5- hexatriene (2 points each).
b. Write the number of nodes in the box to the left of each orbital array (1 point each).
c. For the ground state of 1,3,5-hexatriene, draw the electron population for each
orbital on the line to the right of each orbital array. For each electron, clearly indicate
whether it is “spin up” or “spin down”. If there are no electrons given orbital, leave it
blank (1 point each).
# of nodes
# of Nodes
orbitals
Orbitals
electron
population
Electron
population
5
E
4
3
2
1
0
1 point per box
2 points per orbital array
1 point each
or
1 point per box
2 points per orbital array
1 point each
Figure by MIT OCW.
4
2. (continued)
d. For each reaction shown below, indicates which energy level is used to predict the
stereochemical outcome by shading the appropriate lobes of the entire orbital
array. (The methyl groups are omitted for clarity; you do not have to draw them.)
e. In the box under each reaction arrow, write conrotatory or disrotatory, as appropriate.
f. In the box to the right of each reaction arrow, draw the major product of the reaction,
clearly indicating the relative stereochemistry.
Me
Me
heat
Me
Disrotatory
(trans)
Me
Me
hν
Me
Conrotatory
(cis)
Me
Me
Me
heat
Me
Me
Disrotatory
(cis)
Me
Me
Me
hν
Me
Conrotatory
(trans)
(Shade appropriate lobes)
(write "conrotatory" or disrotatory")
2 points each
1 points each
Me
(draw major product- show
stereochemistry)
3 points each
Figure by MIT OCW.
(shade appropriate lobes)
2 points each
(write “conrotatory” or “disrotatory”)
1 point per box
5
(draw major product – show stereochemistry)
3 points per box
OH Me
H
3. (22 points total) Using retrosynthetic analysis, propose a
synthesis of the molecule to the right (A). You may use any
reagents you wish, as long as your starting materials and any
other reagent that is used to install a carbon that is found in the
final product (target molecule A) have no more than 6 carbon
atoms. For example, 1,3-butadiene and benzene would be
acceptable, but benzyl bromide (PhCH2Br) would not be.
H
Me
O
target molecule (A)
Write your synthesis in the “forward” direction, showing all
Steps and reagents necessary. (You may include solvents, but
you are not required to do so.) Draw a box around or circle
Your final synthesis.
Hint: Use a Diels-Alder reaction.
HO
H
Me
Me
O
Target
O
H
O
H
HO
Me
Me
+
O
O
Me
H
Me
O
Forward Synthesis:
O
Me
+
O
O
O
∆
Diels- Alter
(endo)
Me
Me
HO
H
LiAlH4
O
O
Me
H
Me
HO
Intramolecular
Oxy-mercuration
1.Hg(OAc)2
2. NaBH4
Me
HO
H
H
CH3
O
Product
Figure by MIT OCW.
6