Methanol protonated

Conjugate acid of benzoic acid Methanol Protonated form of tetrahedral intermediate... 

Monoprotonation of the [2.1.1]-cryptand occurs rapidly but protonation of the monoprotonated species by hydronium ion and other acids can be followed kinetically in various solvents (Cox et al., 1982, 1983). In methanol, protonation of ii+ species by substituted acetic and benzoic acids to give i+i+ has been studied using the stopped flow technique with conductance detection. The values of the rate coefficients (kHA) for protonation (81) vary with the acidity of the donor acid from kHA = 563 dm3mol-1s-1 (for 4-hydroxy-benzoic acid) to kHA = 2.3 x 105 dm3mol 1s 1 (for dichloroacetic acid). 

Direct Methanol Proton Exchange Fuel Cell... 

Sridharan and Mathai noticed that the transesterification of small esters under acid-catalyzed conditions was retarded by the presence of spectator polar compounds. " Thus, given that water can form water-rich clusters around protons (solvent-proton complexes) with less acid strength than methanol-only proton complexes, some catalyst deactivation may be expected with increased water concentrations. Also, water-rich methanol proton complexes should be less hydrophobic than methanol-only clusters, thus making it more difficult for the catalytic species (H" ) to approach the hydrophobic TG (and possibly DG) molecules and contributing to catalyst deactivation. Therefore, with water present in the feedstock or produced during the reaction in significant quantities, some catalyst deactivation can take place by hydration. 

The question of methanol protonation was revisited by Shah et al. (237, 238), who used first-principles calculations to study the adsorption of methanol in chabazite and sodalite. The computational demands of this technique are such that only the most symmetrical zeolite lattices are accessible at present, but this limitation is sure to change in the future. Pseudopotentials were used to model the core electrons, verified by reproduction of the lattice parameter of a-quartz and the gas-phase geometry of methanol. In chabazite, methanol was found to be adsorbed in the 8-ring channel of the structure. The optimized structure corresponds to the ion-paired complex, previously designated as a saddle point on the basis of cluster calculations. No stable minimum was found corresponding to the neutral complex. Shah et al. (237) concluded that any barrier to protonation is more than compensated for by the electrostatic potential within the 8-ring. 

Thus the 2 mol equivalents of protons which are necessary to dipro-tonate the coordinated dinitrogen are subsequently regenerated due to the relatively high acidity of coordinated methanol. Protons are consumed only in the neutralization of liberated phosphine. 

There is a discrepancy in the literature concerning 1,2-dihydro-isoquinoline itself. Thus, Huckel and Graner54 report its trimerization to 31 (m.p. 138°, the same melting point that Packham and Jackman11 ascribe to the monomer). It is thought63 that in a nonpolar solvent, 1,2-dihydroisoquinoline is relatively stable, but in methanol, protonation and trimerization occur certainly the mass spectrum of the compound (m.p. 138°) described by Packham and Jackman indicates that it is trimeric.63 The series of 1,2-dialkyl-1,2-dihydroisoquinolines described by Bradley and Jeffry30 was purified by distillation under reduced pressure. The stability of these compounds is quite remarkable in view of the known tendency for 1,2-dihydroisoquinolines to undergo disproportionation. Some other 1,2-dialkyl-1,2-dihydroisoquinolines have been described,7 as well as 1-aryl derivatives.7 The derivative (32) when heated with triethyl phosphite is transformed by an unknown mechanism, in 37% yield, into 33.64... 

The ester carbonyl group is not a strong enough electrophile to react with methanol. Protonation converts it to a strong electrophile (shown in step 3). 

The view of Clinton and Kochi (49) is that this unfounded homolytic decomposition of an alkylcopper and the thermodynamically unfavored abstraction of the methanolic proton are simply explained by protonolysis, as occurs in acetic acid (Eq. (6)]. 

H - methanol proton, H -zeolite proton in the neutral adsorption complex. Results for the free methanol and methoxonium species are also given. 

Recent PMR and UV studies have identified the positions of protonation of compounds 11 and 15. In methanol, protonation of 11 occurs initially at the oxo group to give the monocation 12. In water, however, monoprotonation gives the 1-protonated cation 13. In stronger acid the same dication (14) is formed in both solvents. In both methanol and water the 3-amino compound 15 gives the monocation 16, and then the diprotonated species 17 is formed at greater acidities. 

A common interpretation of this reaction invokes the use of the cerium(lll) chloride as a Lewis acid that bonds to the carbonyl system, to make 1,2-addition favored. However, lanthanoid ions are known to preferentially bind to alcohols rather than carbonyl groups.6 Additionally, if the cerium did bind with the carbonyl, one would expect that as dilution with methanol was increased, the observed regioselectivity, presumably due to this complexation, should be reduced. However, experimental results do not support this hypothesis. Since cerium complexation with methanol would result in increased acidity of the methanolic proton, the following scheme appears to be the more likely course of the reaction. 

A second synthetic example illustrates several useful features of cation rearrangements. When 121 (OPiv is a pivaloyl ester) was treated with p-toluenesulfonic acid in methanol, protonation occurred at the more basic... 

It was also tentatively proposed the chloride attacks the imido cluster generating the equivalent of an acyl chloride, which might then react more easily with methanol. Protonation of the imido nitrogen and reductive elimination would yield the final product, regenerating Ru3(CO)i2. 

Min et al. [35] experimented on high-catalyst loading with 60% carbon and 40% Teflon backing claimed to be the most efficient electrode for direct methanol/proton exchange membrane fuel cell (PEMFC). The catalysts used were platinum and ruthenium which formed an alloy at an atomic ratio 1 1. The formation of the alloy was seen in XRD as there were no pure metal peaks found. The alloy formation of Pt and Ru promotes oxidation of methanol at lower temperatures. The 60% carbon backing makes it evident that the lower the percentage of carbon increases the efficiency. 

When the anion reacts with a molecule of methanol, protonation occurs on the lobe of the p orbital away from the MeO group and the Z alkene is formed. 

R. C. Dunbar, Energy dependence of methanol proton transfer reaction rate, J. Chem. Phys. 52, 2780-2781 (1970). 

Scheme 4.1 Enhancement of the epoxidation activity of framework Ti by coadsorbed methanol. The methanol proton is transferred to form ROH (schematic).

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