Cubane strain energy

In many cases, the strain energies for bicyclic compounds are approximately the sum of the strain energies of the component rings. This is seen with bicyclo[2.1.0]pentane, bi-cyclo[3.1.0]hexane, and many other compounds. It applies even to cubane, in which the strain energy is equal to six times the strain energy of a cyclobutane ring. 

All cubanes are high energy materials and should be handled with due precautions for potential explosives [ 1]. The ring system has almost 700 kJ/mol strain energy (more, per unit weight, than the detonation energy of TNT) and is under study as a basis for high power explosives [2,3]. Cubane itself explodes spontaneously at 3 GPa pressure, the... 

The next Platonic solid is the cube, and the corresponding polycyclic hydrocarbon, cubane, (CH)8 (Figure 3-21c), has been known for some time [49], The strain energy of the CC bonds in cubane is among the highest known. It is unstable thermodynamically but stable kinetically, like a rock [50], Referring to its instability, Marchand... 

Recent advances in the area of cubane chemistry are truly amazing. In fact, the high strain energy of cubane itself should have been taken as an unequivocal... 

Thermochemical data substantiated the highly strained character of 4. In fact, the strain energy per C-C bond of the tetrahedrane skeleton in 4 turned out to be 21.5 kcal mol , the highest value known (c/ data for cubane, vide supra). Why then is it so stable Obviously this is a purely kinetic stability, as was the case with cubane, but the origin of this stability of 4 is rather unusual. It is speculated that the presence of four terf-butyl groups creates a kind of corset ... 

The rearrangements of cage-like structures have been discussed in some detail in refs. 11 and 12, and can be divided into three main classes (i) homocubane to cubane (ii) adamantane to noradamantane and (iii) homoadamantane to twist-brendane and these are depicted (together with strain energy estimations from ref. 79) in Scheme 39. It can be seen that in each case rearrangement provides a system with... 

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