Strain in Polycyclic Molecules

Knowing the importance of angle and eclipsing strain in the small-ring cycloalkanes, we should expect that these strains would become still more important in going from cyclobutane to bicyclo[1.1.0]butane or from cyclooctane to pentacyclo[4.2.0.02,5.03 8.04,7]octane (cubane). This expectation is borne out by the data in Table 12-6, which gives the properties of several illustrative smallring polycyclic molecules that have been synthesized only in recent years. 

Another extraordinarily strained polycyclic hydrocarbon that has been prepared in recent years is prismane (the Ladenburg structure for benzene, see Exercise 1-6). 

This substance is a liquid that decomposes explosively when heated. In dilute solution at 100°, it is converted slowly to benzene. 

Exercise 12-28 Name prismane according to the system described in Section 12-8. 

Exercise 12-29 Draw a sawhorse-style formula for bicyclo[1.1.0]butane and formulas for all of the eight possible dichlorobicyclof 1.1.0]butanes (including chiral forms). 

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