Organic Chemistry III

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 H^o = 0.8 kcal/mol for each gauche interaction.
   

2. 
   a. Write out all possible conformational forms of 1-methylquinolizidine. Ignore enantiomers.
   

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.
   

4. 
   Explain why cyclohexane derivative shown prefers the conformation with the methyl group axial (B) rather than equatorial (A).
   

5. 
   Predict which isomer is preferred, and briefly explain why.
   

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 H_f^o 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.
   

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

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.)