Protonated methyl alcohol

Because the protonation of ozone removes its dipolar nature, the electrophilic chemistry of HOs, a very efficient oxygenating electrophile, has no relevance to conventional ozone chemistry. The superacid-catalyzed reaction of isobutane with ozone giving acetone and methyl alcohol, the aliphatic equivalent of the industrially significant Hock-reaction of cumene, is illustrative. 

Wender and coworkers conclude that cobalt-catalyzed benzyl alcohol homologation involves the intermediate formation of car-bonium ions (8). However, since the methyl cation (CH3+) is unstable and difficult to form (9), it is more likely that methanol homologation to ethanol proceeds via nucleophilic attack on a protonated methyl alcohol molecule. Protonated dimethyl ether and methyl acetate forms have been invoked also by Braca (10), along with the subsequent formation of methyl-ruthenium moieties, to describe ruthenium catalyzed homologation to ethyl acetate. 

Shida and Hamill23 found that the positive and negative molecular ions of 1,3-butadiene and its homologs have similar absorption spectra. Band maxima of the anions are not sensitive to substituent alkyl groups, whereas those of the cations are red-shifted as the number of substituent methyl groups increases. In alcoholic matrices the butadiene anions abstract the alcoholic proton to form an allylic radical (equation 23), as was proven by ESR spectroscopy. 

Abstract-—The hydrogen bonding chemical shift of the —OH proton of methyl alcohol has been separated into two parts, one due to the formation of dimer and the other to all other polymeric species. A molecule which is hydrogen bonded as dimer contributes only about one-third as much as a molecule in a higher polymer. The separation is based on correlation with the —OH stretching infrared data, and is confirmed by the examination of sterically hindered alcohols—both aromatic and aliphatic—which because of bulky substituents, can form dimers but not higher polymers. In these substances, the small H-bond shifts are also correlated with monomer-dimer equilibrium studies of the infrared spectra. 

Figure 4.2. H NMR spectrum of protonated methyl alcohol in HS03F-SbF5-S02 at — 60°C.

Whereas the C2—C4 alcohols are not carboxylated under the usual Koch-Haaf conditions, carboxylation can be achieved in the HF-SbF5 superacid system under extremely mild conditions.400 Moreover, Olah and co-workers401 have shown that even methyl alcohol and dimethyl ether can be carboxylated with the superacidic HF-BF3 system to form methyl acetate and acetic acid. In the carboxylation of methyl alcohol the quantity of acetic acid increased at the expense of methyl acetate with increase in reaction time and temperature. The quantity of the byproduct dimethyl ether, in turn, decreased. Dimethyl ether gave the desired products in about 90% yield at 250°C (90% conversion, catalyst/substrate ratio =1 1, 6h). On the basis of experimental observations, first methyl alcohol is dehydrated to dimethyl ether. Protonated dimethyl ether then reacts with CO to yield methyl acetate [Eq. (5.154)]. The most probable pathway suggested to explain the formation of acetic acid involves the intermediate formation of acetic anhydride through acid-catalyzed ester cleavage without the intervention of CO followed by cleavage with HF [Eq. (5.155)]. 

Which atoms in proUmated mcthylamine iCHs NH ) and protonated methyl alcohol iCHjOH . ) carry A formal charge Uae SpartanView to examine the electrostatic potential map fur each ion, and identify the most positive atom in each. Do the for-m l charge asrtgnnneiiu agree with the e lectriwtatk potential maps ... 

Busch, J. H., and de la Vega, J. R., Symmetry and tunneling in proton transfer reactions. Proton exchange between methyloxonium ion and methyl alcohol, methyl alcohol and methoxide ion, hydronium ion and water, and water and hydroxyl ion, J. Am. Chem. Soc. 99,2397-2406 (1977). 

The first reproducible results demonstrating efficient dinitrogen reduction with participation of protons were reported in 1970 [15]. Table 2 lists systems reducing N2 in the presence of water or methyl alcohol. They are mainly based on V and... 

It should also be noted fhat fhe boundary line of Ad values is tilted to the right side, as indicated by fhe dotted hne in 69a (Fig. 9.21), i.e. fhe MaNP plane dividing the space into two sectors of Ad is moved from the regular position of the C4—Cl hne to fhat of C4—CIO. This phenomenon implies fhat the MaNP ester moiety dechnes toward fhe aliphatic side of C-3, not toward fhe aromatic side of C-4a, because of steric hindrance. This conformation was in fact proved by the X-ray crystallographic analysis of ester 69a, which indicated fhat fhe ester plane was tilted from the alcohol methine proton plane by 41.7° to fhe methylene side at the C-3 position [45]. The Ad data of trons-methyl alcohol esters 70a/70b are similar to those of esters 69a/69b except for that of the methyl group, leading to the (3k,4S) absolute configuration of (-h)-70a. 

We realize from the above discussion that care must be exercised in deciding whether a substance has acidic or basic properties. Usually we are limited to the behavior of the substance in water. The fact that, in water, a compound develops neither acidic nor basic properties signifies merely that its acidic and basic properties are weaker than those of water, and does not prove that the substance is unable to supply or accept protons. Monovalent alcohols for example are weaker bases and (except for methyl alcohol) weaker acids than water. Addition of a small quantity (about 1%) of alcohol to an aqueous solution of an acid or base accordingly will effect scarcely any change. 

The reactions were carried out in isopropyl alcohol. This compound was selected as solvent because the natural lifetime of the aromatic radical anion with respect to protonation (1, 3) is longer than in methyl alcohol or ethyl alcohol. The isopropyl alcohol was obtained from Mathe-son, Coleman, and Bell and was freshly distilled over sodium metal through a glass-packed column for each set of runs. Anthracene from Matheson, Coleman and Bell, pyrene from Aldrich Chemical Co., m-terphenyl and p-terphenyl from City Chemical Corp. were purified as described (2). 9,10-Dimethylanthracene obtained from K and K Laboratories, Plainview, N. Y., was recrystallized from isopropyl alcohol solution. 

The resulting H3O ion can now transfer a proton to another H2O molecule. In other words, protons, although not free in solution, can be passed from one water molecule to another. Calculations from the known structure of water show that the proton must jump a distance of 0.086 nm (0.86 A) from an HsO ion to a water molecule, but that as a result the proton moves effectively through a distance of 0.31 nm (3.1 A). The conductivity by this mechanism therefore will be much greater than by the normal mechanism. This proton transfer must be accompanied by some rotation of HsO" " and H2O molecules in order for them to be correctly positioned for the proton transfers. Similar types of mechanisms have been proposed for other hydroxylic solvents. In methyl alcohol, for example, the process is ... 

Formed in superacid media species exhibiting electrophilic properties are able to attack alkanes primarily via electrophilic addition to C-H bond followed by other reactions. In particular, Olah et al. observed O atom insertion in hydrogen peroxide reaction with methane in Magic Acid above 0 °C to produce methanol with very high (>95%) selectivity [54a]. The particle (OH)"", which may be considered to be a protonated oxygen atom in the singlet state is apparently the active species in the reaction. Methyl alcohol formed is immediately protonated to methyloxonium ion, and this prevents further... 

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