Simple prismanes

Using this method we may now show in simple terms that the conversion from prismane to benzene is forbidden. In this case the three breaking (T-bonds of prismane (shown dotted in Figure 10a) are transformed into the three benzene functions in... 

The radical cation derived from bic.yclopropenyl (129) is of interest a) because it is the only benzene isomer with any degree of conformational mobility, b) as a potential intermediate in the rearrangement of prismane radical cation (cf., the 2B2 state, Scheme 12), and c) as a potential adduct between cyclopropenium cation and cyclopropenyl radical. It has proved practical to study a simple (3,3 -dimethyl-) derivative (131) of this species, because this precaution eliminates the prototropic rearrangement to the conjugated isomer. 

Other problems, such as non-orientability, also contribute to making this a poor fix to a much deeper problem, especially for models whose geometry is not heuristically simple. See the discussion of triangular prismane vs. triangular Moebiane in [79]. 

Strain than simple cyclopropanes or cyclobutanesTable 4.5 shows a few of these compounds." Perhaps the most interesting are cubane, prismane, and the substituted... 

Let us close this account of simple prismanes with a look at hexaprismane. The synthesis of cubane was reported in 1964 pentaprismane was said (1974) to show extraordinary synthetic inaccessibility [16], but was made in 1981 [13] and hexaprismane has so far (early 2007) resisted all attempts at synthesis [5]. As Hopf points out [5], hexaprismane can in principle be assembled from two benzene rings or from cyclobutadiene and cyclooctatetraene ... 

Another factor, besides strain, that can destabilize a molecule is an unfavorable electronic interaction, for example that manifested as antiaromaticity, in, say cyclobutadiene [39], but unlike strain, electronic interactions can be favorable and stabilizing. Minyaev et al. proposed that orbital interactions between the two capping (CH)n and the adjacent C moieties stabilize [3 n]- and [4,n]-prismanes by CT-overlap of rr-type ring orbitals, and precedent for snch stabihzation in simple... 

There is as yet no evidence for the existence of simple polymeric chains based on linked P4 units as in (4.168), but several clusters (Pn) appear to be energetically favourable with respect to P4, according to calculations [54,55]. The unknown prismane Pg (4.29) should be more stable than a flat hexagonal ring [56], although the transition 2P4 Pg is not favoured enthalpically or entropically [29]. 

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