Due: Monday, November 2,
2009
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Ozone
In 1840, Christian
Friedrich Schönbein
(1799-1868) discovered ozone (Gr.; odorant), the sharp
odor produced by electrical discharges. Seven years later
(1847) he observed that ozone oxidizes organic compounds
but not to their ultimate products of oxidation, carbon
dioxide and water. [Two years prior, he had spilled
nitric and sulfuric acid on his Frau's apron in her
kitchen. The apron, made of cotton, combusted and thus
was discovered gun cotton, nitrocellulose. Schönbein
also observed that hydrogen peroxide (Threnard; 1818) is
oxidized to oxygen gas in the presense of hemoglobin.
] In the period 1903-1916, Carl
Dietrich Harries (1866-1923),
an assistant to both Hofmann (of the eponymous
elimination and rearrangement) and Fischer (of projection
and carbohydrate fame) at Berlin, published some 80
papers on the reactions of ozone with organic compounds.
His interest was stimulated by the reaction of ozone with
rubber, a process that causes rubber to become hard and
brittle. These studies led to the analytical and
synthetic uses of ozone. From 1904-1916 he was a
professor at Kiel. Disenchanted with academic life, he
became Director of Research for Siemens and Halske, the
German company co-founded by the electrical pioneer,
Werner von Siemens, his father-in-law. Not surprisingly,
Siemens went into the business of producing ozone
generators. The studies of Rudolf
Criegee (1902-1975;
Karlsruhe)
produced a unified mechanism for the process
of ozonolysis.
M.
Rubin, Bull. Hist. Chem., 2001, 26,
40.
M. Rubin, Helv. Chem. Acta,
2003, 86, 930.
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Reading assignments:
a)The alkene module
in
ORGO.
b)
Ozonolysis
module.
How do I approach solving problems
like #1---5? Here
is a step-by-step analysis of a typical problem.
1. An optically active compound A
(C8H14) reacts with catalytic
OsO4 and stoichiometric
H2O2 to form (R,R)-diol
B. Ozonolysis and dimethyl sulfide reduction of
A forms OHC(CH2)6CHO. What
are the structures of A and B?
Explain.
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Vladimir Vasilovich
Markovnikov
(1838-1904)
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2. Compound A,
C7H12, [Degree
of Unsaturation?] affords
a
single
ketoaldehyde B upon ozonolysis and dimethyl
sulfide reduction. Hydrogenation of A gives
methylcyclohexane. Treatment of A with HBr in the
presence of
peroxide
gives two stereoisomeric bromides, C and D.
Compound C reacts with
C2H5ONa/C2H5OH
to give E while under the same conditions,
compound D gives mainly A and some of
compound E. Ozonolysis of E gives a single
dialdehyde F. What are the structures of
A-F? Explain and illustrate. Pay attention to
stereochemistry.
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3. Compound A reacts with
Br2 in CCl4 to give B. The
intermediate in this reaction (C) is a racemic
species. Ozonolysis of A affords only propanal
(propionaldehyde). What are the structures A-C?
Explain and illustrate. Pay attention to
stereochemistry.
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4. Optically active terpene A
reacts with 2 molar equivalents of hydrogen to produce
diastereomers B and C, both of which are
optically inactive. Compound B has a smaller heat
of combustion than C. Ozonolysis and dimethyl
sulfide reduction of A affords pyruvaldehyde
D (C3H4O2,
Google
it) and (S)-isopropylsuccindialdehyde E
(OHCCH(i-Pr)CH2CHO; tartaric acid =
2,3-dihydroxysuccinic acid). What are the structures
A-E? What are the sign and value of the optical
rotation of A (Review PS4)?
Explain.
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5. Compound A
(C10H20) undergoes ozonolysis to
produce a
single,
optically active compound
(R)-B. The reaction of compound A
with ethereal OsO4 or aqueous KMnO4
provides a
single,
optically active compound
C. What are the structures of A-C? Show
their stereochemistry. Show your reasoning.
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6. Provide the products, reagents,
and/or reagents as required in each of the following
problems. Explanations are required for all.
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