Class Summary          11/10/04          Term Paper Guidelines         

 

IMPORTANT DATES            Wed., Dec. 1st              First draught of paper due

                                                Wed., Dec. 8th             Review of other papers due

                                                Tues., Dec. 14th            Final Exam

                                                Fri., Dec. 17th               Final Paper Due

 

11/10   Origins of Strain (Isaacs text)

 

1)                  Prelog Strain – intermolecular crowding (steric hindrance)

(tBu)3CX                      (Tidwell, 1978)

Hexaphenylethane         (McBride, 1974)

Ph3C·                           (Gomberg, 1900)

2)                  Baeyer Strain – bond angle distortion

3)                  Pitzer Strain – torsional deformation about s-bonds (staggered vs. eclipsed)

 

Impacts of Strain          Bredt’s Rule (Bredt, 1924) – avoid forming double bonds at bridgehead atoms

 

            Anti-Bredt Olefins

                        (Jones, 1998) – proposed anti-Bredt intermediate, not directly observed

                        (Warmuth, 2003) – used hemicarcerands to directly observe anti-Bredt intermediate

                        (Jones/Platz, 1991) – homocubene vs. cubylidene

 

PAPERS MENTIONED

 

Gomberg, M.  An Instance of Trivalent Carbon:  Triphenylmethyl  J. Am. Chem. Soc. (1900) 22, 757-771.

 

Bredt, J., Thouet, H., Schmitz, J.  Steric hindrance in the bridge ring (Bredt’s rule) and the meso-trans-position in condensed ring systems of the hexamethylenes  Liebigs Ann. Chem. (1924) 43(7?), 1-13.

 

McBride, J. M.  The hexaphenylethane riddle  Tetrahedron (1974) 30, 2009-2022.

 

Tidwell, T.T.  Sterically crowded organic molecules: synthesis, structure and properties  Tetrahedron (1978) 34, 1855-1868.

 

Chen, N., Jones, M., White, W.R., and Platz, M.S.  Equilibrium between homocub-1(9)-ene and homocub-9-ylidene  J. Am. Chem. Soc. (1991) 113, 4981 – 4992.

 

Ruck, R.T. and Jones Jr., M.  Bicyclo[2.2.1]heptan-1-ylcarbene can ring expand  Tetrahedron Lett. (1998) 39, 4433 – 4436.

 

Roach, P., Warmuth, R.  The Room-Temperature Stabilization of Bicyclo[2.2.2]oct-1-ene and Bicyclo[3.2.1]oct-1-ene  Angew. Chem. Int. Ed. (2003) 42, 3039-3042.

 

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