,
Problem Set 6
Chapter 7, Structure and Synthesis of Alkenes
Due: Monday, March 3, 2008
1. Read Degree
(Elements) of Unsaturation. How
many degrees of unsaturation are present in
C8H3BrClN3O2?
Draw a structure that has the number of degrees of
unsaturation you determined and that is necessarily in
agreement with the formula. 4. Compound A
(C5H11Cl) reacts readily with water to
form B, C5H12O. Exposure of
compound A to aq. NaOH gives only C (major)
and D (minor). Hydrogenation of C liberates
27.0±0.1 kcal/mol heat while D liberates 28.5
kcal/mol of heat during hydrogenation. What are the
structures A-D? Explain. 5. a) Determine the heat of hydrogenation
of cyclohexene from the heat
of formation tables. b) How does
this value compare with the heat of hydrogenation of an
unstrained cis-disubstituted double bond? c) Given the heat
of hydrogenation of cyclopentene (chapter 7) determine the
heat of formation of cyclopentene. d) BONUS: Why is the heat
of hydrogenation less for cyclopentene than that for
cyclohexene? Show all work. 6. Two stereoisomers, A and
B, absorb one equivalent of hydrogen upon catalytic
hydrogenation to form cyclooctane. Compound A, which
is capable of resolution, liberates 34.5 kcal/mol of heat
while B liberates 24.3 kcal/mol of heat. 7. Comment critically on the following
proposed synthesis of the now banned gasoline additive,
methyl tertiary-butyl ether (MTBE). If you believe the
reaction will be successful, provide the type of mechanism
that is operable and illustrate it with the curved arrow
formalism. If you feel that the reaction will not be
successful, state the expected product of the reaction and
the mechanism by which it is formed. Illustrate with curved
arrows. If no reaction takes place, state so and explain why
not.
2. a) Estimate the DHfo
of 2-methylpentane from the heat of formation of
2-methylheptane.
Show work.
b) Estimate the heat of formation of 2-methyl-1-pentene from
the heat of hydrogenation of 2-methyl-1-butene, using Table
7-1 (pg. 292, 6th ed.; pg.285, 5th ed.). Show work.
c) Again using Table 7-1, estimate the heat of isomerization
of 2-methyl-1-pentene into 2-methyl-2-pentene. Show
work.
3. a) [2.2.2]-Bicyclooctane forms how many
monochloro constitutional isomers upon free radical
chlorination? What are their structures?
b) In what ratio are they expected to be formed? Show
work.
c) Are they optically active, racemic, or achiral?
d) How many different alkenes are formed from the monochloro
compounds upon treatment with a strong base? Explain and
illustrate.
Paul
Sabatier
1912 Co-Nobel Prize in Chemistry
Hydrogenation by Metal Catalysis
a) What are the structures of A and B ?
b) What are the heats of formation of A and B
?
c) What is the difference in strain energy between A
and B ?
d) What is the difference in the heat of combustion between
A and B?
e) Why is A capable of resolution?