Magic acids

The high acidity of superacids makes them extremely effective pro-tonating agents and catalysts. They also can activate a wide variety of extremely weakly basic compounds (nucleophiles) that previously could not be considered reactive in any practical way. Superacids such as fluoroantimonic or magic acid are capable of protonating not only TT-donor systems (aromatics, olefins, and acetylenes) but also what are called (T-donors, such as saturated hydrocarbons, including methane (CH4), the simplest parent saturated hydrocarbon. 

This book is mainly about my life in search of new chemistry. Because some of my work centered around the discovery of extremely strong superacids, which are sometimes also called magic acids, I chose the title A Life of... 

Maghemite [12134-66-6] Magic acid Magic Acid MagicAcid [33843-68-4] Magic Carpet system Magma... 

The term magic acid coined in G. A. Olah s laboratory for the non-aqueous system HSOaF/SbFs. 

An even stronger acid ( Magic Acid ) results from the interaction of SbFs with an oxygen atom in fluorosulfuric acid HSO3F (i.e. HF/SO3) ... 

Antimony pentachloride is a reactive Lewis acid that can be used for Friedel-Crafts reactions and some other Lewis-acid-catalyzed reactions. The HF-SbF5 system is known as magic acid, and carbocations are stabilized in this medium.353 By using the HF-SbF5 system, alkylation of acetophenone (a relatively unreactive aromatic compound) has been achieved (Scheme 87). 

Urea and substituted ureas have also been shown to be O-protonated in anhydrous media, with a second protonation ensuing on one of the N atoms in pure fluorosulphuric acid and in magic acid (Birchall and Gillespie, 1963 Olah and White, 1968). 

Both O- and N-protonated cations of N-acylaziridines have been observed by nmr spectroscopy, the first in HSO3 F—SbFs —SO2 at —60°C, and the second as the hexafluoroantimonate in liquid SO2 at —60°C (Olah and Szilagyi, 1969). Presumably pure liquid sulphur dioxide is a better stabilizing medium for N-protonated cations than the magic acid mixture. 

Numerous Lewis acids promote the formation of nitronium ions when in the presence of nitric acid. Nitric acid-boron trifluoride, and the nitric acid-hydrogen fluoride-boron trifluoride reagents described by Olah are practical nitrating agents the latter provides a convenient preparation of nitronium tetrafluoroborate. Olah reports that nitric acid-magic acid (FSOsH-SbFs) is extremely effective for the polynitration of aromatic substrates. 

MACROSCOPIC DIFFUSION CONTROL MICROSCOPIC DIFFUSION CONTROL Magic acid,... 

The trihydroxyyclopropenium ion (175) shows a single absorption in its C NMR spectrum, 128.7, which can be ascribed to the monoprotonated deltic acid from the DFT/IGLO calculations. Interestingly, the cation does not form the diprotonated species (176) even in Magic Acid (//q = -22). 

The four-, five-, and six-membered analogs (178,180, and 182) were also obtained from the diprotonation of squaric acid (3,4-dihydroxy-3-cyclobutene-l,2-dione, 177), tri-O-protonation of croconic acid (4,5-dihydroxy-4-cyclopentene-l,2,3-trione, 179), and tetra-O-protonated rhodizonic acid (5,6-dihydroxy-5-cyclohexene-l,2,3,4-tetraone, 181), respectively. These ions were prepared in either Magic Acid (1 1 FSOsH-SbFs) or fluorosulfuric acid at low temperature and characterized by NMR. Ab initio/IGLO calculations showed that di-O-protonated squaric acid (178) is planar and aromatic, whereas the polyprotonated croconic and rhodizonic acids (180 and 182) have more carboxonium ion character, and no indication was obtained for any significant contributing homoaromatic structures. 

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