Diprotonated propane dication

On the potential energy surface of diprotonated propane (C3H102+), three structures were located as minima (MP2/6-31G level).788 The 1 -//,2-//-diprotonated and 1-/7,3-//-diprotonated forms (458 and 459) are of Cj and C2v symmetry, respectively, whereas the l-//,C-diprotonated structure (460) has C symmetry. Structure 459, a distonic dication with the two charge-bearing centers separated by one carbon, is significantly more stable (by 22.6 kcal mol-1) than structure 458 (a gitonic dication with adjacent charges) and also more stable than structure 460 (by 6.9 kcal mol ). 

For diprotonated isobutane (C4H122+) the structures found as stable minima are analogous to those computed for diprotonated propane (C3H102+). Again, structure 478 (a distonic dication) is 17.7 kcal mol 1 more stable than structure 479 (a gitonic dication), whereas structure 480 is only slightly less stable than 478 (2.6 kcal mol-1).788... 

In addition to the carbenium-carbonium dications (i.e. 35), bis-carbonium dications have been studied by theoretical methods. Examination of the potential energy surface of C3Hio2+ (diprotonated propane) finds three structures at energy minima.18 The global minimum corresponds to the structure (37) in which both terminal carbons are involved in electron-deficient 2e-3c bonds. The next most stable C3Hio2+ structure (38) lies 6.7 kcal/mol higher in energy and it possesses two 2e-3c bonds,... 

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