Strain small ring compounds, table

TABLE 4.5 Some Strained Small-Ring Compounds... 

Small ring compounds such as cubane and norbomane arc strained for obvious reasons. Larger rings tend to be less strained, as perusal of Table 6 will show. 

The diazirine precursors of carbenes (entry 3 in Table 10.3) are cyclic isomers of diazo compounds. The strain of the small ring and the potential for formation of nitrogen make them highly reactive on photoexcitation. They are, in general, somewhat less easily available than diazo compounds or arenesulfonylhydrazones. However, there are several useful synthetic routes.86 87 88... 

Conformational analysis of rings larger than cyclohexane is more complicated. These rings are also less common than cyclohexane, so we discuss their conformations only briefly. As can be seen from Table 6.1, the seven-membered ring compound cycloheptane has only a small amount of strain. Obviously, it is nonplanar to avoid angle strain. It does have some torsional strain, but the overall strain is comparable to that of cyclopentane. It is a fairly common ring system. 

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