Chem 331
Exam 3
2011
Prof. Fox
50 minutes
The exam is open book,
Open notes. Models are permitted
Show your work in detail
WRITE YOUR NAME ON EVERY PAGE
NAME
Chem 331, Exam 3. 2011
!
!
NAME
1. The reactions shown below would not proceed as shown. Explain why (be concise), and indicate which product
would be formed instead.
a.
H
H
O
OEt
O
OEt
O
O
O
(5 pts each)
OH
HO
H+
Aldehydes react with alcohols or diols to form acetals. Esters do not. The product would be:
O
H
OEt
O
b
Me
1) MeLi (large excess)
O
O
H3C
O
O
O
2) H3
CH3
HO
O+ (workup)
The lactone (a cyclic ester) would also react with MeLi. The product would be
HO
H3C
CH3
OH
HO
c
H
O
Me Me
1) excess EtMgBr
O
O
2) H3O+ (workup)
OH
both the aldehyde and epoxide would react with EtMgBr. The product would be:
HO
OH
O
O
Chem 331, Exam 3. 2011
!
!
NAME
2. Propose a synthesis for 1 starting with any materials that contain 4 carbons or less. You may also use reagents
that contain more than 4 carbons (e.g. Ph3P, LDA, MCPBA, DIBAL, DCC, pyridine, TsCl, Et3N).
(25 points)
retrosynthesis
N
O
H2N
N
O
OH
1
O
N
N
BuLi
forward synthesis
N
mCPBA
Li
N
OH
O
H3O+ workup
tBuOH, H+
H2N
O
LiAlH4
N
O
Li
Chem 331, Exam 3. 2011
!
!
NAME
(20 pts )
3. Propose the structure of 2. Provide a mechanism for it's formation.
2
OH
O
NMR
110.2, s
69.6, t, 2 carbons
29.8, t, 2 carbons
20.8, t, 2 carbons
catalytic H+
HO
13C
C7H12O2
1H
NMR
3.90–3.80 (m, 4H)
2.06–1.81 (m, 4H)
1.90–1.80 (m, 4H)
H
OH
HO
OH
O
OH
H+
+O H
O
+O
OH
OH
OH
+ 2
OH
H+
O
O
O
O
O
H +
+
HO
+
O
HO
resonance
stabilized
Chem 331, Exam 3. 2011
!
!
NAME
4. Propose a detailed arrow pushing mechanism
(20 pts )
Cl
MeO
HCl
OMe
MeO
H
+
OMe
resonance
stabilized
Cl–
H+
MeO
OMe
H
MeO
+
OMe
+
: OMe
+
MeO
H
Cl
MeO
H