AUMQIC
Exam 4
Chem 22
April 22, 2010
^
(
Name
page
c\ r\
0
3
-
1 (20)
2 (35)
total (200)
3 (40)
chk
4 (40)
5 (35)
6 (35)
Please resist the temptation to deface this space.
.
1 (20 points) (a) Draw the most stable enol tautomer (if any) of each carbonyl compound below.
ocH
!
•4, 1* .
(b) Rank the carbonyl compounds above according to the amount of enol present at equilibrium,
with 1 indicating the most enol and 4 indicating the least.
The third carbonyl compound, 2-methylcyclohexanone, is chiral. Starting with either
enantiomer of this ketone, write a mechanism to show how this compound racemizes in the
presence of aqueous acid .
(c)
Fu*)T 2. (20 points) Write the mechanisms of the two reactions below and draw the products. Show
+
every step explicitly, including all proton transfers; do not use "+H+" and "-H " abbreviations.
\o
\0
(a ) base-catalyzed hemiacetal hydrolysis
cv
( b) base-induced lactone hydrolysis
3. (15 points) Write a mechanism that accounts for the following transformation. Show each step
clearly with curved arrows. Hint: no other product is formed in significant yield. 4. (25 points) As promised, here's a problem from the last HW set. Write the complete
mechanism, showing every step clearly.
>
&
MS
*^0)", A./
O
/ rs
^ to explain the following reaction.
15 points Write a mechanism
.
)
5. (
seen before; methane is produced as a byproduct.)
—
(This is one that you haven't
*, 6. (25 points) Draw the products of the following reactions, including stereochemistry, where
relevant. Label products to indicate stereoisomeric relationships as appropriate.
6
O
1 . Ph3P:
.A
2. nBu-Li
1
(b)
y-
>-
-78°C
»>
CH3CH2-I
•
.N. e
Li+
LQ 0
!
NaBD4
EtOH
1
m
*
.
7 ( 15 points) How would you convert benzyl bromide to the unsaturated ketone below, using
only compounds from the Chemical Store (2nd to last page of this exam)?
PhCH2Br
-
C vO.
* h
3
o
9 n
8. ( 35 points) Show how you would make the following compounds from malonic ester and any
of the other compounds in the Chemical Store .
(a )
o
<
‘OEt
,C Tt OtCf f
&
^ '=
-Aww-taf "a>s
• 9. (20 points) Suggest a synthesis of the aldehyde below by using only compounds available in
the Chemical Store.
(a )
y&&
&
.
10 (15 points) How would you carry out the following transformation? Use any reagents you
feel are appropriate.
\ u94-l(om
^
Chemistry 221 Exam 4 2010
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