Methanol ionization potential

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

The difference between the ionization potential of methanol (10.9 e.v.) and the appearance potential of CH2OH + (11.9 e.v.) (4) is sufficiently large that, by controlling the electron energy, Reaction I can be studied to the effective exclusion of Reaction N. 

A mixture of water/pyridine appears to be the solvent of choice to aid carbenium ion formation [246]. In the Hofer-Moest reaction the formation of alcohols is optimized by adding alkali bicarbonates, sulfates [39] or perchlorates. In methanol solution the presence of a small amount of sodium perchlorate shifts the decarboxylation totally to the carbenium ion pathway [31]. The structure of the carboxylate can also support non-Kolbe electrolysis. By comparing the products of the electrolysis of different carboxylates with the ionization potentials of the corresponding radicals one can draw the conclusion that alkyl radicals with gas phase ionization potentials smaller than 8 e V should be oxidized to carbenium ions [8 c] in the course of Kolbe electrolysis. This gives some indication in which cases preferential carbenium ion formation or radical dimerization is to be expected. Thus a-alkyl, cycloalkyl [, ... 

Lewis Bases. A variety of other ligands have been studied, but with only a few of the transition metals. There is still a lot of room for scoping work in this direction. Other reactant systems reported are ammoni a(2e), methanol (3h), and hydrogen sulfide(3b) with iron, and benzene with tungsten (Tf) and plati num(3a). In a qualitative sense all of these reactions appear to occur at, or near gas kinetic rates without distinct size selectivity. The ammonia chemisorbs on each collision with no size selective behavior. These complexes have lower ionization potential indicative of the donor type ligands. Saturation studies have indicated a variety of absorption sites on a single size cluster(51). 

Fio. 12. Fhotoelectron spectrum of methanol vapour using the helium resonance line (21-21 e.v.). Ionization energy increases from left to right. The adiabatic ionization potentials measured (Al-Jobomy and Turner, 1964) are indicated by vertical arrows, and can be compared with (probably) vertical I.P. values derived from electron impact appearance potentials by Collin (1961) (dotted arrows). 

The acridizinium (benzo[6]quinolizinium) ion, being isoelectronic with anthracene, is fluorescent (55JA4812). The fluorescent quantum yield for acridizinium perchlorate in methanol was reported to be 0.52 (80MI21000). The rate of quenching of this fluorescence by alkyl halides was found to be related to the ionization potential of the halide (78MI21001). Quenching by anions was also measured (79JPR420). 

In the second mechanism, the electron transfer from the nucleophile cluster into the aromatic ring should be facilitated by the decrease of the ionization potential (IP) of the solvent clusters as n increases. This mechanism is convincing for the ammonia or methanol clusters which show relatively low IPs when cluster size is increasing however, for water clusters, the IPs of n > 3 clusters are not known. The IPs of water and its dimer are 12.6 and 11.2 eV, respectively (Ng et al. 1977). However, these IPs are certainly higher than the one of PDFB (9.2 eV), which is not in favor of a sequential electron transfer followed by a proton transfer mechanism. This mechanism is more likely possible if one assumes, in agreement with Brutschy and coworkers, that the barrier to the reaction is lowered by a concerted electron transfer/proton transfer mechanism (Brutschy 1989, 1990 Brutschy et al. 1988, 1991, 1992, in press). 

Dougherty (1975) has pointed out that the first ionization potential (IP) of a solvent may reflect its nucleophilicity. Earlier we had considered this possibility, but were disappointed to find a lack of correspondence between the two parameters (Table 8). The IP of water is over 2 eV higher than that of ethanol, whereas water and ethanol have similar N values. The IP of acetic acid is also less than that of the more nucleophilic methanol. However, in agreement with qualitative expectations, the IP of 2,2,2-trifluoroethanol is higher than the other, more nucleophilic alcohols, and the IP of... 

Talamoni and coworkers17 found that in methanol, allylamine has no influence on the yield of 0-Ps. Other amines, such as w-propylamine and triethylamine, increase the yield of the o-Ps. The authors ascribe this difference to the higher ionization potential of allylamine, making positive charge transfer from the solvent ions (the holes) ineffective. The ionization potential of allylamine (9.6 V) is considerably higher than that of other amines (w-propylamine 8.8 eV, triethylamine 7.8 eV, aniline 7.7 eV). They found a correlation between the ionization potentials and the enhancement factors. In water, allylamine also enhances the formation of 0-Ps, due to the much higher ionization potential of water, 12.6 eV (while the value for methanol is only 10.8 eV). 

Three-ring organosulfur compounds have an ionization potential (IP) that ranges around 8 eV, which is lower than that of methanol (10.85 eV), so that electron abstraction from an organosulfur compound should be favored over abstraction from methanol when an organosulfur compound is present. Thiophene and benzo[3]thiophene have an oxidation potential in excess of -I-1.8V versus NHE and are not oxidized prior to the solvent in the mixture. 

Selective synthesis of 2-methyl naphthalene has been studied over HZSM-5, HZSM-11, HSABO-11, HZBS-11, Zn-ZSM-11, Ga-ZSM-11, HY and HZSM-20 type zeolites. The nature of the naphthalene-methanol interaction has been investigated in order to elucidate the reaction mechanism. According to the data obtained by FT-IR, TPD of naphthalene, ionization potential and proton affinity of different aromatic rings, zeolites with medium pores and with sites of medium or high acid strength are necessary for the reaction. The results seem to be consistent with the Rideal type mechanism. 

Ionization potential of Continued) butenone, 123 cyclic diacetylenes, 305 cyclohexene, 48, 102 cis-cyclooctene, 102 Zraus -cyclooctene, 102 DABCO, 81 dimethyl ether, 123 ethylene, 80, 319 formaldehyde, 123, 319 hydrogen atom, 55, 75 methanol, 123 methyl acetate, 123 methyl acrylate, 123 nitrous oxide (N2O), 172 norbornadiene, 48 norbornene, 48 oxetane, 123 tetrahydrofuran, 123 trimethylamine, 81 water, 123... 

It is qualitatively apparent that reactions of methanol ion will be enhanced at higher ionizing voltages since the ionization potential of methanol exceeds that of acetaldehyde by approximately 0.64 e.v. (30). Unfortunately, quantitative measurements in the range where only acetaldehyde ions should be observed is not practical with our equipment because of lack of sensitivity and the energy spread of the electron beam. However, earlier investigations by Hutchison and Pobo (16) and Harrison et al. (10,12, 26, 27) have shown that relative cross sections can be obtained quantitatively on the following basis. 

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