Chem 0130
Dennis P. Curran
March 28, 2012
Exam 3
Name:_________________________________
Signature:______________________________
Seat:__________________________________
Answer all questions on this exam. If you need more space than that
provided, use the back of any page.
1.____________________ (20 points)
Names and Structures
2.–––––––––––––––––––– (20 points)
Short Answer Questions
3.–––––––––––––––––––– (30 points)
Reaction Products
4.____________________ (10 points)
Mechanisms
5.____________________ (20 points)
NMR Spectroscopy
Total_________________ (100 points)
The test has 7 pages (including this cover page) and 5 questions
The exam ends at 10:55 am sharp.
Good Luck !!!
–page 1–
1) Structures and Names (20 points)
a-d) Provide IUPAC names for the following compounds.
Be sure to include cis/trans, R/S, if needed. (3 points each)
OCH3
a)
b)
Cl
OH
OH
c)
d)
O
O
e, f) Provide clear structures for the following names.
Be sure to show stereochemistry if relevant. (4 points each)
e) cyclopentyl isopropyl ether
f) (2R,3R)-3,4,4-trimethyl-2-hexanol
-page 2-
2) Short Answer Questions (30 points)
a) Indicate whether each of the following transformations is
an oxidation, a reduction, or neither.
O
H
O
H
O
OH
O
H
O
O
OH + HOCH3
O
CH3
+ H2O
b) Provide a specific example of a solvolysis reaction.
Show the starting material, the product(s), and all reaction components.
-page 3-
c) State whether the following reactions provide: 1) an achiral product; 2) a
mixture of enantiomers, or 3) a mixture of diastereomers.
O
O
MgCl
NaBH4
THF
CH3OH
O
NaBH4
CH3OH
d) Rank the following cations in order of increasing stability (that is, most stable last).
+
+
CH3CH2+
FCH2CH2+
e) Tetramethyloxacyclopropane gives an unexpected product in the reaction with
NaOCH3. Why is the expected product not formed? Show a reasonable
mechanism for formation of the actual product.
O
NaOCH3
HO
CH3OH
tetramethyl
oxacyclopropane
OH
OCH3
expected product,
not formed
-page 4-
actual product
3) Reaction Products (6 x 5 pts = 30 pts)
Show all expected products of the following reactions. Be sure to indicate
stereochemistry, if relevant. NOTE: numbers "1), 2)" mean two separate
reactions with workup in between.
1) PCC, CH2Cl2
a)
2) CH3MgBr, THF
OH
b)
CH3
O
CH3OH
CH3CH2
CH3
cat H2SO4
O
2 equiv LiAlH4
c)
O
d)
OH
THF
1) SOCl2
2) NaOCH2CH3,
HOCH2CH3
dry HBr
e)
gas
OH
OH
excess Na2Cr2O7
f)
H2SO4, H2O
CH2OH
-page 5-
4) Mechanisms (10 points)
Show detailed mechanisms for each of the following two reactions. Show all
individual steps, including acid/base reactions. Use arrows to track electron flow.
a)
THF/H2O
OH
2% NaOH
O
OH
b) Show the mechanism for both steps.
O
1) CH3MgBr, THF
2) aqueous H2SO4 workup
-page 6-
CH3
5) NMR Spectroscopy (20 points)
a) Indicate the number of resonances (peaks) expected in the broadband (proton)
decoupled 13C NMR spectra of the following componds (6 points).
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
b) Indicate the expected multiplicities (splittings) for all the protons in the following
bis-ether (6 points).
H3C
H2
C
O
O
C
H2
H
C
CH3
CH3
c) Below are listed the 1H NMR spectral data for sec-butyl ethyl ether (2ethoxybutane). Assign each resonance to the relevant protons (6 points).
O
sec-butyl ethyl ether
(2-ethoxybutane)
1H
NMR, δ 3.7 (1H, sextet), 3.5 (2H, quartet), 1.6 (2H, quintet), 1.3 (6H, two
overlapping triplets), 1.0 (3H, doublet)
d) In the 13C NMR spectrum of sec-butyl ethyl ether (above), how many
resonances will be above 50 ppm and how many resoances will be below 50
pmm? (2 points)
-page 7-