Problem Set 6
Chapter 7
Due: Monday, October 18, 2004
1. Read Degrees (Elements) of
Unsaturation here
and/or here.
How many degrees of unsaturation are present in
C4H5BrClNO2? Draw a
structure that has the number of degrees of unsaturation you
determined and that is necessarily in agreement with the
formula. a) How does your answer compare with the
typical value reported in Table 7-1 on pg. 285?
Explain. b) Find the heat of formation of
cyclooctane. Why is its value nearly the same as that of
cyclohexane and not ~-40 kcal/mol? c) The heat of hydrogenation of
cis-cyclooctene is -24.3 kcal/mol. What is its heat of
formation? Show work. d) What accounts for the difference in
the heats of hydrogenation of cyclohexene and
cis-cyclooctene? e) The heat of hydrogenation of
trans-cyclooctene is -34.5 kcal/mol. What is the heat of
isomerization of the geometrical stereoisomers of
cyclooctene and in what direction does it occur? Place the data above in a chart that
relates all of the the heats relative to the steady
state. 4. Optically active alkyl chloride
A (C6H13Cl) is converted into a
mixture of two hydrocarbons B and C (major)
upon exposure to CH3ONa/CH3OH.
Compound (R)-B liberates 30.2 kcal/mol of heat
upon hydrogenation while compound C liberates 26.2
kcal/mol. A stereoisomer of A, namely D, when
treated with CH3ONa/CH3OH affords
(S)-B and E. Compound E
liberates 25.8 kcal/mol of heat upon hydrogenation. The
hydrogenation product F of B, C, and
E is achiral. Free radical bromination of F
gives monobromide G, which, when treated with
CH3ONa/CH3OH, gives C,
E, and H, all three of which have the same
formula. What are the structures and IUPAC names of
A-H? Explain and illustrate. 5. Achiral compound A
(C9H16) is inert toward
hydrogenation. Free radical chlorination of A
provides four (theoretically) monochloro compounds: primary
achiral B (11%), secondary (±)-C and
(±)-D in 68% combined yield, and tertiary
achiral E (21%). There is much less D formed
than C even though they arise from the same carbon
radical. Compound A reacts reluctantly with NaOH at
elevated temperatures to give F
(C9H18O). No products of elimination
are formed. Upon exposure to NaOH, compounds C and
D give G (C9H16).
Compound E is inert toward NaOH. a) What are the structures A
through G? Explain. b) Why is less D formed than
C? Explain. 6. Complete each of the following
questions. Provide brief explanations.
2. Do problems 2-4 in the Alkyl Halide module in
ORGO.
They need not appear on your homework.
3. Find the heat of hydrogenation of cyclohexene using the
Heat
of Formation tables.
Paul
Sabatier
1912 Co-Nobel Prize in Chemistry
Hydrogenation by Metal Catalysis