Organic Chemistry III
Exercise I
Due Date: Oct. 4, 2008
1. Calculate the difference in enthalpy between cis and trans decalins by counting the number of
gauche-butane interactions. Use Ho = 0.8 kcal/mol for each gauche interaction.
2. a. Write out all possible conformational forms of 1-methylquinolizidine. Ignore enantiomers.
CH3
1-Methylquinolizidine
N
b. Which forms interconvert with which (without bond breaking)? Note that both ring
reversaland nitrogen inversion can take place (in contrast to 1-methyldecalin).
c. Count the number of gauche-butane interactions for each structure in (a). In each set of
interconverting forms, which one(s) is(are) the major conformational isomer(s)?
3. Characterize the indicated protons as being stereohomotopic, enantiotopic, or diastereotopic.
CH3
Cl
a.
Cl
H
H
CH2C6H5
CH2C6H5
b.
c.
H3C
CH3
O
e.
H
d.
F
Cr(CO)3
C
C
H
Cl
HOH2C CH3
O
H
g.
f.
H
H3C
CH
CH3
CH3
H
H
OH
4. Explain why cyclohexane derivative shown prefers the conformation with the methyl group
axial (B) rather than equatorial (A).
CH3
CH3
CH3
CH3
CH3
H3C
A
B
5. Predict which isomer is preferred, and briefly explain why.
CH3
CH3
N
C
N
D
6. Series E and F can be viewed as two different ways to annulate an ethano bridge onto four-,
five-, and six-membered rings. Using the Hfo values given (in kcal/mol), calculate the strain
energy for each compound. Briefly discuss whether the trend seen in each series is consistent
with expectations based on additivity of ring strain.
H
H
H
H
H
H
25.63
0.51
-6.1
16.37
-12.42
-23.04
E
F
7. What are the major contributions of the Nobel laureates listed in the handout?
• 2005 Yves Chauvin, Robert H. Grubbs,
Richard R. Schrock
• 2001 Williams S. Knowles, Ryoji Noyori,
K. Barry Sharpless
• 2000 Alan Heeger, Alan G. MacDiamid,
Hideki Shirakawa
• 1996 Robert F. Curl, Jr., Harold W. Kroto,
Richard E. Smalley
• 1994 George A. Olah
• 1990 Elias J. Corey
• 1987 Donald J. Cram, Jean-Marie Lehn,
Charles J. Pedersen
• 1984 Bruce Merrifield
• 1983 Henry Taube
• 1981 Kenichi Fukui, Roald Hoffmann
• 1979 Herbert C. Brown, Georg. Wittig
• 1976 William Lipscomb
• 1975 John Cornforth, Vladimir Prelog
• 1973 Ernst O. Fischer Geoffrey Wilkinson
• 1969 Derek Barton, Odd, Hassel
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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1965 Robert B Woodward
1963 Karl Ziegler, Giulin Natta
1961 Melvin Calvin
1957 Alexander R. Todd
1953 Hermann Staudinger
1950 Otto Diels, Kurt Alder
1947 Robert Robinson
1938 Adolf Butenandt, Leopold Ruzicka
1938 Richard Kuhn
1937 Norman Haworth, Paul Karrer
1930 Hans Fischer
1928 Adolf Windaus
1927 Heinrich Wieland
1915 Richard Wilstaetter
1913 Alfred Werner
1912 Victor Grignard, Paul Sabatier
1910 Otto Wallach
1905 Adolf von Baeyer
1902 Emil Fischer
8. A recent photophysical study of the following polymer suggests a -stacked structure shown
below. Based on your knowledge of conformational analysis, comment it critically [Hint:
Consider the interlayer distance in graphite].
(T. Nakano and T. Yade , Chem. lett., 2008, 37, 258.)