Chem 220a
Problem Set 8
Chapter 9
Due: Monday, November 1, 2004
Connections
Aluminum was once a precious metal
although it was plentiful. The problem was how to remove
it from its ore. Friedrich
Wöhler, of urea synthesis
fame, was able to accomplish this feat but by an
impractical method. He was to meet a young chemist,
Frank
Jewett, recently arrived in
Gottingen from Yale. Aware of the difficulty Wöhler
had had and probably encouraged by Wöhler, Jewett,
as a professor at Oberlin College, passed the problem
onto Charles
Martin Hall, a young student
at the college. Hall solved the problem in his family
garage. Thus was born Alcoa. At the same time,
Thomas
Willson, a Canadian, and
American James Moorhead were unsuccessfully trying to
refine aluminum in Spray, NC using an electric arc.
Unsuccessful in purifying aluminum, they sought calcium
metal. Heating coal tar and lime in an electric furnace
they obtained a brittle material that produced a
combustible gas upon exposure to water. The material was
not calcium nor was the gas hydrogen. The pair was
calcium carbide and acetylene. Thus was born Union
Carbide.
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The alkyne module in ORGO
gives a good review of acetylene chemistry.
1. Two bottles are labeled "A -
C8H14" and "B -
C8H14". Compound A liberates 65
kcal/mol of heat upon hydrogenation to form n-octane.
Compound B also provides n-octane upon hydrogenation.
When treated with Na/NH3, A forms
C. Compound C undergoes ozonolysis to form a
single substance D. Compound B forms
succindialdehyde E (Cf. pg. 903) and F.
Treatment of B with Br2/CCl4
provides two racemic tetrabromides, G and H.
What are the structures A-H? Explain and illustrate.
[G and H are not
distinguishable.]
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2. Design a synthesis of muscalure. As
your sources of carbon, you have acetylene, 1-bromopentane,
and 2-octyne available to you. All reagents are also
available.
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3. When (Z,Z)-1,5-cyclooctadiene
is treated with borane at ambient temperature, two boranes
(C8H15B) A and B are
formed. When the mixture is heated at elevated temperature,
only A is observed and the mass balance is excellent
(i.e., B is not destroyed.). Treatment of A
with alkaline peroxide converts A into achiral
C (C8H16O2). The
diastereomer of C, namely D, which is not
formed, is also achiral. When B is exposed to
alkaline peroxide, compound E is formed. E is
achiral but its diastereomer F is a racemate.
a)What are the structures of A-F?
Explain and illustrate all reactions.
b) When 1-hexyne is exposed to A,
G is formed. G reacts with alkaline peroxide
to form H and C. What are G and
H? Provide mechanisms (curved arrow formalisms) for
the formation of C and H.
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4. In the first column is a list of 19
compounds. Their assigned numbers are in the second column
that is labeled From. For example, you are being
asked to convert 1 To 2, 13, 3, and 4. The first
transformation is how do you go from 3-hexyne (1) to
1-hexyne (2). You are to make a list 1 ---> 2 "answer"
for each of the 25 transformations. If a number appears
twice in a row (e.g., two sixes in row 3), this means that
their are two answers. These transformations require one or
two steps. Imagine that you were asked to prepare 8 from 1.
You can work this synthesis backwards (or forwards) from 8
--> 5 --> 4 --> 1 by following the red
numbers.
Compound
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From
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To
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To
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To
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To
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3-hexyne
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1
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2
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13
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3
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4
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1-hexyne
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2
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16
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11
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12
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18
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(E)-3-hexene
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3
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6
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6
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9
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10
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(Z)-3-hexene
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4
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10
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5
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17
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17
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cis-2,3-diethyloxirane
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5
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8
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trans-2,3-diethyloxirane
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6
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10
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d,l-3,4-dibromohexane
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7
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2
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d,l-3,4-dihydroxyhexane
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8
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meso-3,4-dibromohexane
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9
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meso-3,4-dihydroxyhexane
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10
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hexanal (Table 18-3)
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11
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2-hexanone (Table 18-3)
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12
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3-hexanone (Table 18-3)
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13
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2-hexanol (Table 10-1)
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14
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1-hexanol (Table 10-1)
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15
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1-hexene
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16
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2
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14
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15
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19
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3-hexanol (Table 10-1)
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17
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2-heptyne
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18
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1-bromohexane
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19
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15
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16
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14
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