Superacidity protonic

It has been shown, however, that such catalysts may contain protons, either by design or because of the difficulty in removing all traces of moisture, and these protons have been shown to be superacidic with Hammett acidities up to —18. These protons will also play some role in the catalytic activity of these ionic liquids in practical situations. Ionic liquids in which superacidic protons have deliberately been generated by addition of small amounts of water, HCl or H2SO4 have been used to catalytically crack polyethene under relatively mild conditions. The main products are mixed C3-C5 alkanes, which would be a useful feedstock from waste polyethene recycling. In contrast to other cracking procedures no aromatics or alkenes are produced, although small amounts of polycyclic compounds are obtained. 

In superacids protonation of isobutane leads to pentacoordinate carbocations, the interconversion of which scrambles all hydrogens inclusive of the methine... 

Superacidic protonation of MePF2 was also used to prepare the salts MePF2H+MF6 (M = As, Sb).556 The cations show distorted tetrahedral structure and weak P—F interionic contacts. 

The Ni-catalyzed oligomerization of olefins in ionic liquids requires a careful choice of the ionic liquid s acidity. In basic melts (Table 5.3-10, entry (a)) no dimerization activity is observed. Here, the basic chloride ions prevent the formation of free coordination sites on the nickel catalyst. In acidic chloroaluminate melts, an oligomerization reaction takes place even in the absence of a nickel catalyst (entry (b)). However, no dimers, but a mix of different oligomers, are formed by cationic oligomerization. Superacidic protons and the reactivity ofthe acidic anions [Al2Cl7] and [Al3dio] may accoimt for this reactivity. 

Zeolites.- Zeolites with high silicon to aluminium ratio such as H-mordenite or H-ZSM-5 are sometimes considered as superacids. The reason for such classification is that the BreSnsted centres of the zeolites act in a similar way to protons in superacid solution. It is however, necessary to point out that such centres, in spite of certain similarity to superacid protons, are less active. n-Alkane reaction takes place in the presence of zeolites at temperatures above 523K. Hydroxyl groups interacting with aluminium polymeric compounds (AlO) are responsible for... 

Al202-Pt/AlEtCl2. HCl, alkanes undergo acid-base reactions with a superacid proton ... 

Bronsted superacids Proton donor acids stronger than 100% sulfuric acid. 

Conjugate Bronsted-Lewis superacids Superacidic proton donor acids comprised of a combination of Bronsted and Lewis acids. 

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