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According to the authors, what happens is that dehydration leads to cis carbocatió type 9 while the

Another type of aromaticity: the hiperaromaticitat | CatQuímica.cat
The aromaticity is a property that presents some organic and inorganic cyclic compounds with conjugated double bonds. This electronic delocalization in these compounds gives them great stability. The aromatic benzene example is shown in Figure 1. We do not think, but it is a rare property, on the contrary, of the 20 million compounds identified chemie about 2/3 are partially or fully aromatic.
The classic aromatics are benzene and polycyclic benzene derivatives, the aromatic hydrocarbons políciclis. Over time, chemists have found similar or identical properties to the typical aromaticity in different chemie aromatic compounds have called by different names and so we talk about heteroaromaticitat such as pyridine, metal on metal as loaromaticitat lobenzens, homoaromaticitat such as the 3-cation bicycles [3.1.0] hexyl, as quasi-aromaticity in the ring generated by bond formation chemie by resonance-assisted chemie hydrogen bridge, Möbius aromaticity in ciclononatetraenil cation, three-dimensional aromaticity or spherical as in fullerenes, homoaromaticitat spherical as Si8Li2 but also aromaticity σ (as in the cation Li3 +), aromaticity δ or aromaticity φ in certain clusters chemie of metal (Cu4Li2 or Ta 3 O 3 -) or you Multiple aromaticity as in [Al4] 2 - or Hf3. In all these compounds chemie have a common electronic cyclic delocalization chemie that provides stability, as in the classic aromatic systems. And we n'oblidéssim of antiaromaticitat 4n systems such as ciclobutadiè.
Well, recently O'Ferrall and collaborators have proposed yet another type of aromaticity, called hiperaromaticitat. The proposal comes in the wake of the study of the reaction of dehydration of cis and trans 1,2-aromatic dihidrodiols like Figure 2. The authors found that the compounds cis (two hydroxyl groups pointing in the same direction) dehydrate 5,000 times faster than the trans. This is an unexpected result and the authors make the assumption that there has to define hiperaromaticitat.
According to the authors, what happens is that dehydration leads to cis carbocatió type 9 while the transformation takes carbocations of type 10 as can be seen in Figure 3. The carbocatió 9 has a pseudoaxial CH is perfectly willing to interact with the p orbital of hiperconjugació carbocatió. This stabilizes and facilitates the reaction of diols cis compared to trans. The electronic charge hiperconjugació put the link antibonding CH and facilitates breakage, which can be represented as shown in Figure 4, where we form a compound chemie 2b clearly aromatic. Suffice to say that the fact that this type of aromatic carbocations are already defended for years Ragué Paul von Schleyer, although he did not use the term hiperaromàtic and has been proven recently by Patrick W. Fowler with the calculation chemie of ring currents. In short, through a system generated hiperconjugació aromatic and hence the name hiperaromaticitat one more to the long list of different chemie aromaticitats. And the aromaticity (like Messi) never cease to amaze us and help us!
Tagged: Aromaticity
[...] Co-director of this thesis) and we talked about a new type of aromaticity, the hiperaromaticitat, collaborative blog CatQuímica. In his entry on Michael as we mentioned many types of aromaticity and did not know [...] Aromatic Interactions "CatQuímica.cat July 19th, 2011 5:02 pm
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