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Magic Acid protonation

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. [Pg.100]

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). [Pg.335]

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. [Pg.335]

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. [Pg.255]

Dimethylbutane and 2,3-dimethylbutane in Magic Acid—S02C1F solution at —78°C give the same distribution of products, a roughly 3 2 mixture of dimethyl-isopropylcarboxonium ion (19) and protonated acetone (20)67 (Scheme 9.5). This clearly demonstrates that, in contrast with the transformation of the abovementioned compounds, ozonation in this case proceeds via the intermediate carbocation 18. [Pg.447]

Concentration effects on 13C shifts of alcohols are small [271]. Solvent-induced shifts are enhanced on going from primary to tertiary alcohols and may be as high as 2 ppm [271]. Protonation shifts are much larger. The methanol carbon, for example, is shielded by —14.6 ppm relative to the neat liquid value when dissolved in magic acid [272], Protonation shifts of 1-alkanols in trifluoroacetic acid are shieldings for C-1 and alternating deshieldings for all other carbon atoms, e.g. <5 2 > > <5C 3 for 1-butanol [272],... [Pg.207]

The benzenonium ion, obtained by dissolving benzene in magic acid , behaves correspondingly Only one signal with <5C = 144.5 ppm is recorded at — 80 °C due to rapid proton migration. An averaged one-bond carbon-proton coupling of 26.5 Hz is expected... [Pg.304]

Lammertsma and Cerfontain411 have obtained the cyclopropyldicarbinyl dication 197 by diprotonating the l,6-methano[10]annulene in much stronger Magic Acid at 60°C [Eq. (3.49)]. If the same protonation was carried out at — 120°C, they were able to obtain the previously discussed monocation 106.284... [Pg.154]

Lammertsma412 has also obtained dication 198 by the protonation of hexahydro-pyrene in Magic Acid solution. This is the first example of a p,p -diprotonated naphthalene derivative. Koptyug and co-workers270,413 have studied a,a -diproto-nated hexa- and octamethylnaphthalenes 199 under superacidic conditions. [Pg.154]

Alkylcarboxonium ions may be synthesized easily by the dehalogenation of a-haloethers. In Magic Acid, first the oxygen is protonated to oxonium ion 319, which, upon increasing temperature, decomposes to yield alkylcarboxonium ion 320 [Eq. (3.87)].624 In a similar manner, protonation of a-alkoxyacetic chlorides625 or acids626 also leads to carboxonium ions. The latter approach was used to generate cyclic alkylcarboxonium ion 321 [Eq. (3.88)]. [Pg.186]

Even diazomethane has been protonated708 in the superacid media. In Magic Acid media, both methyldiazonium ion 397 as well as iV-protonated diazomethane 398 are formed [Eq. (3.113)]. [Pg.202]

In the case of phenols, either C- or (9-protonated ion 12 or 13 are formed, depending upon the acidity of the medium. In relatively weak acid medium such as H2SO461 only O-protonation is observed. However, in HSO3F only the C-protonated species is formed.62 In a much stronger acid system such as HSC F-SbFs (Magic Acid), both C-or O-protonated dication 14 can be observed. Both the C- and O-protonated ions were shown to exist in the gas phase by IR photodissociation spectroscopy.63... [Pg.317]

The synthesis under stable ion conditions and characterization by 1H, 13C, and 29Si NMR spectroscopy of the [(trimethylsilyl)methyl]oxonium ion 15 have been reported by Olah et al.67 Protonation of the corresponding alcohol with Magic Acid gives ion 15, which is stable and can be isolated at room temperature [Eq. (4.9)]. [Pg.318]

The study of 2,6-disub stituted benzenediazonium ions492 did not show the presence of any persistent C-protonated benzenediazonium dication even in Magic Acid [Eq. (4.138)], reinforcing the notion that charge delocalization into the aromatic ring plays a significant role. [Pg.386]

For this reason when Magic Acid (HS03F-SbF5,1 1 molar ratio) is used under the same experimental conditions as above at room temperature, isobutane undergoes very slow ionization and the formation of the ferf-butyl ion can be monitored. However, recovered isobutane shows no exchange because the reversible protonation via carbonium ion transition state does not take place and because the ferf-butyl ion, stable in this solution at room temperature, does not deprotonate. [Pg.516]

Because neither hydrogen peroxide nor Magic Acid-S02C1F alone led to any reaction under the conditions employed, the reaction must be considered to proceed via electrophilic hydroxylation. Protonated hydrogen peroxide inserts into the C H bond of the alkane. A typical reaction path is as depicted in Scheme 5.60 for isobutane. [Pg.661]

It is well-recognized that phenols are completely protonated in superacidic solutions.420 This raised the possibility that protonated phenols, once formed in these media, might resist further electrophilic attack. Electrophilic hydroxylations of aromatics with hydrogen peroxide (98%) in superacidic media has been achieved by Olah and Ohnishi617 in Magic Acid, which allows clean, high-yield preparation of monohydroxylated products. Benzene, alkylbenzenes, and halobenzenes are efficiently hydroxylated at low temperatures. The obtained yields and isomer distributions are shown in Table 5.36. Subsequently, Olah et al.618 found that benzene and... [Pg.663]

Straight-chain alkanes also efficiently react with ozone in Magic Acid at —78°C in SO2CIF solution. Ethane gave protonated acetaldehyde as the major reaction product together with some acetylium ion (Scheme 5.62). Reaction of methane, however, is rather complex and involves oxidative oligocondensation to terf-butyl cation, which reacts with ozone to give methylated acetone (Scheme 5.63). [Pg.670]

Finally, it is noteworthy that direct n.m.r. evidence on the formation of edge-protonated cyclopropanes in cold solutions of magic acid containing c-CsHg was recently reported (Olah and Lukas, 1968). [Pg.140]

Much interest has been devoted to the related stable (f/ -bicyclo[5.1.0]octa-2,4-di-enylium)Fe(CO)3 cation complex, mainly in connection with the question of the possible homoaromaticity of these cations (equation 148) . The complex was first prepared by the formal electrocyclic ring closure of protonated (cyclooctatetraene)Fe(CO)3 at -60 (Scheme 7) and has later been proved by NMR studies in magic acid solutions... [Pg.554]


See other pages where Magic Acid protonation is mentioned: [Pg.133]    [Pg.133]    [Pg.98]    [Pg.100]    [Pg.192]    [Pg.164]    [Pg.286]    [Pg.286]    [Pg.142]    [Pg.262]    [Pg.22]    [Pg.447]    [Pg.494]    [Pg.554]    [Pg.13]    [Pg.22]    [Pg.174]    [Pg.201]    [Pg.343]    [Pg.460]    [Pg.509]    [Pg.672]    [Pg.866]    [Pg.53]    [Pg.134]    [Pg.135]    [Pg.646]    [Pg.132]    [Pg.689]   
See also in sourсe #XX -- [ Pg.154 , Pg.174 , Pg.202 ]




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