Proponium cations

Figure 13. Snapshots of the BOMD of l-H-proponium cation, its rearrangement to C-proponium cation andfurther decomposition.

Figure 14. Superimposed structures of the BOMD of the 1-H-proponium cation.

Kebarle. " Recently, Mota et al. calculated the potential energy surface of the C3H9+ cation [MP4(SDTQ)/6-311++G /MP2(full)/6-31G level]).The C-proponium cation (43) was again found to be of lowest energy but the complex xec-C ilh + H2 lies only 0.3 kcal mol above structure 43. The C-H bond lengths in the 3c-2e interactions are 1.272 and 1.188 A, whereas the C-C bond distance is 2.099 A.They also found that the interconversion between the -H-protonated cation (45) and the C-proponium cation (43) has no energy barrier. This may indicate that on zeolites where steric effects are important the primary, that is more accessible hydrogens are protonated initially to yield the... 

Ab initio topological analysis of the proponium cations showed that the most stable structure is the C-proponium ion lying, however, only 0.3 kcal mol below the van der Waals complex of isopropyl cation and H2 (MP4/6-311-H-G / MP2/6-31G level of theory). Similar topological studies of the stability of the different n-butonium cations formed by the protonation of the nonequivalent bonds of n-butane indicated the MP2 level stability order... 

Organic. - Okulik et a/. " looked at proponium cations at ab initio level and typified six different stable structiues four proponium cations and two van der Waals complexes. A topological analysis of p in the C-proponium cation shows significant differences with respect to structures of the H-proponium cations. The detection of an unstable CP and the larger ellipticity found for the C-H and H -H bonds made clear why these species undergo a structural change. 

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