Methyl cations, monosubstituted

The preparation of acetic acid represents a special case. Olah and coworkers as well as Hogeveen and coworkers have demonstrated that CO can react with methane under superacidic conditions, giving the acetyl cation and by subsequent quenching acetic acid or its derivatives (see Section 7.2.3). Monosubstituted methanes, such as methyl alcohol (or dimethyl ether), can be carbonylated to acetic acid.115 Similarly, methyl halides undergo acid-catalyzed carbonylation.115,116 Whereas the acid-catalyzed reactions can be considered as analogs of the Koch reaction, an efficient Rh-catalyzed carbonylation of methyl alcohol in the presence of iodine (thus in situ forming methyl iodide) was developed by Monsanto and became the dominant industrial process (see Section 7.2.4). 

Proton magnetic resonance techniques have been used for the measurement of rates of hydrogen-deuterium exchange of pyrazine (in CHsOD-CHsONa at 164.6") (591) for a study of protonation of pyrazine (1472) for analysis of the reaction mixture from quatemization of 2-substituted pyrazines with methyl iodide (666) for elucidation or confirmation of the structures of alkylpyrazines obtained by alkylation of pyrazines with aldehydes and ketones in the presence of a solution of an alkali or alkaline earth metal in liquid ammonia, or a suspension of these metals in other solvents (614) for a study of changes in chemical shifts produced on ionization of 2-methyl and 2-amino derivatives of pyrazine in liquid ammonia (665) for characterization of methoxymethylpyrazines (686) for the determination of the position of the A -oxide function in monosubstituted pyrazine V-oxides and the analysis of V-oxidation reactions (838) for a study of the structure of the cations of fV-oxides of monosubstituted pyrazines (1136) and for the determination of the structure of the products of peroxyacetic and peroxysulfuric acid iV-oxidation of phenyl- and chlorophenylpyrazines (733b). 

The reaction of Mn(CO)5Br with methyl isocyanide in THF has been studied under a variety of conditions. Treatment at room temperature for 48 h yields [Mn(CO)3(CNMe)2Br], refluxing for 6 h yields [Mn(CO)2(CNMe)3Br] and refluxing for 24 h gives a mixture of [Mn(CO)2(CNMe)3Br], [Mn(CO)-(CNMe)4Br], and [Mn(CO)(CNMe)g]Br. The monosubstituted product, [Mn(CO)4(CNMe)Br] is obtained from a reaction between Mn2(CO)gBr2 and CNMe and the series of cationic complexes [Mn(CO)e- c(CNMe)J from treatment of [Mn(CO)5 (CNMe) Br] with aluminium trichloride and CO(x = 1—4). The reactions of Mn(CO)sX (X = Q or Br) and CNPh in THF have been reinvestigated as part of this study. The product distribution is again found to depend on the conditions employed and the compound previously reported... 

Some new reactions involving intermolecular reactions of fluoroaryl-substituted stabilized carbanions are summarized in Schemes 7—10. Studies on monosubstituted diethyl malonates have shown that the effect of a penta-fluorophenyl group on the acidity of the C—bond in this system is comparable to the effect of a 2- or 4-nitrophenyl group. Tris(polyfluoroaryl)methyl radicals have also (c/. Scheme 10) been generated by treatment with chromium(n) perchlorate of the corresponding cations generated from tris(polyfluoroaryl)carbinols and trifluoroacetic acid. ... 

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