Ethyl 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. 

H NMR, 4, 1042 ionization potentials, 4, 1046 synthesis, 4, 1066 UV spectra, 4, 1044 Selenolo[2,3 -cjthiophenes H NMR, 4, 1042 synthesis, 4, 1067 UV spectra, 4, 1044 Selenolo[3,2-6]thiophenes dipole moments, 4, 1049 H NMR, 4, 1042 ionization potentials, 4, 1046 synthesis, 4, 1066 UV spectra, 4, 1044 Selenolo[3,4-6]thiophenes synthesis, 4, 1067 Selenolo[3,4-c]thiophenes addition reactions, 4, 1062 synthesis, 4, 1076 Selenomethionine applications, 4, 970 Selenophene, 3-acetamido-reactions, 4, 953 Selenophene, 2-acetyl-mercuration, 4, 946 nitration, 4, 947 Selenophene, 2-alkyl-reactions, 4, 45 synthesis, 4, 135, 967 Selenophene, 3-alkyl-synthesis, 4, 135, 967 Selenophene, 3-aryl-synthesis, 4, 963 Selenophene, 2-benzyl-reactivity, 4, 946 Selenophene, 2-benzyl-5-ethyl-reduction, 4, 950... 

In 1977, Scharf and Mattay [123] found that benzene undergoes ortho as well as meta photocycloaddition with 2,2-dimethyl-1,3-dioxole and, subsequently, Leismann et al. [179,180] reported that they had observed exciplex fluorescence from solutions in acetonitrile of benzene with 2,2-dimethyl-l,3-dioxole, 2-methyl-l,3-dioxole, 1,3-dioxole, 1,4-dioxene, and (Z)-2,2,7,7-tetram-ethyl-3,6-dioxa-2,7-disilaoct-4-ene. The wavelength of maximum emission was around 390 nm. In cyclohexane, no exciplex emission could be detected. No obvious correlation could be found among the ionization potentials of the alkenes, the Stern-Volmer constants of quenching of benzene fluorescence, and the fluorescence emission energies of the exciplexes. Therefore, the observed exciplexes were characterized as weak exciplexes with dipole-dipole rather than charge-transfer stabilization. Such exciplexes have been designated as mixed excimers by Weller [181],... 

In spite of these deviations, the ionization potential rule still has considerable predictive value, although it may be a little too restricted to cover all the addends [116,184], A slight modification of the rule was introduced by Gilbert et al. [12] who proposed that it might be more meaningful to relate the relative effi-ciences of the meta and ortho photocycloaddition with the difference in ionization potential only within a series of structurally very similar alkenes. It was also recognized that ionization potentials relate to properties of the ground state of the reactants rather than of the excited state [185], Nevertheless, the IP rule retains its predictive value in a series in which various arenes are irradiated in the presence of the same alkene [133], Ethyl vinyl ether and benzonitrile (IP = 10.02 eV) yield... 

In spite of the favourable steric arrangement, propargyl cations, although more stable than vinyl and ethyl cations, are less stable than allyl cations. This is indicated by the ionization potentials of the simple parent radicals, 8-25 and 8-16 eV (Lossing, 1963) respectively, and by the lower (by a factor of ca. 104) rate of unimolecular solvolysis in ethanol-water 4 1 of propargyl (174) than of allyl halides (175) (Burawoy and... 

Let us look more closely at such cations, using the parent allyl cation, CH2 CH—CH2, as our example. Bond dissociation energies showed us that allyl radicals are unusually stable, and we attributed this stability to resonance between equivalent structures (Secs. 6.24-6.25). The ionization potential (188 kcal) of the allyl radical enables us to calculate that the allyl cation, too, is unusually stable. Even though we have just drawn its structure as that of a primary cation, it is 24 kcal more stable than the ethyl cation, and just about as stable as the isopropyl cation. We can now expand the sequence of Sec. 5,18. 

The ionization potentials (IP), electron affinities (EA), and absolute electronegativities of fluoroalkyl radicals are useful in order to elucidate the nucleophilic and electrophilic reactivities of the fluoroalkyl radicals. Table 1.36 summarizes available IP and EA data, indicating that (1) all of the a-fluoromethyl radicals have lower IPs than methyl radicals in spite of the strong inductive effect of the fluorine atom, and (2) trifluoromethyl and pentafluoroethyl radicals are, of course, more electrophilic than methyl and ethyl radicals because of their higher values of EA [30]. The former result may arise from the electron-donating conjugation of lone-pair electrons on the fluorine atom, and the latter is due to the strong inductive effect of the fluorine atom. 

We recall that ethyl cation has a bridged, nonclassical structure, and that the classical CH3CH2+ is calculated by high level quantum chemical calculations (36) to be ca. 6 kcal mol 1 less stable. Combining this difference with the experimentally measured heats of formation of ethyl cation and of the neutral ethyl radical, we derive the "classical" ionization potential of CH3CH2 to be 8.4 eV = 193 kcal mol"1. Consider now the geminally-fluorinated ethyl radicals CH3CF2 ,... 

CF3CH2-, and CF3CF2 . The ionization potentials of the first two radicals, 7.9 eV and 10.6 eV (= 182 and 244 kcal mol 1) are consistent with our earlier logic. By analogy to CH3 and CF3, were CH3CF2 planar it would be expected to have an ionization potential no higher than the parent unfluorinated ethyl radical. However,... 

By contrast, perf luoro/ir-f luoro effect reasoning correctly suggests B-fluorination of ethyl radical will increase the ionization potential because the species is nonplanar. For perfluoroethyl radical, the two fluorination effects on ionization potentials run counter to each other. Experiment does not help us decide which effect dominates because the heat of formation of C2F5+ is known no better than 15 kcal mol"1. That is, from appearance potentials of this ion from C2F5Z with Z = F, I, CF3 and C2F5 we obtain ionization potentials of 228, 218, 208 and 199 kcal mol"1 (ca. 9.88, 9.45, 9.02 and 8 63 eV). This is clearly too wide of a spread of values to be of thermochemical use to derive meaningful substituent effects. 

This type of interaction is possible with thiophenol and anthracene whose ionization potentials are, respectively, 8.3 and 7.5 eV [345], but less probable with ethyl- and butylamine which have ionization potentials close to that of pyridine (respectively, 9.19 and 8.79) [345]. Amines and thiophenol can also interact with the radicals formed in the polymer according to... 

From the adiabatic ionization potential of ethyl radical, 8.117 0.008 eV determined by photoionization mass spectrometry and AfH°n,(C2Ft5) = 28.35 0.41 kcal mol from Ref. 96. Thermal corrections as in Ref. 95. 

The relative product distribution produced by photons of 10-e.v. energy in the krypton resonance radiation photolysis will also be taken as representative of excited neutral decomposition induced by electron impact at energies exceeding the ionization potential of ethyl chloride (10.9 e.v.). That is, the contribution to the radiolysis products from excited neutral molecule decomposition will be assumed to have the same relative distribution as that observed in the photolytic decomposition. While superexcited molecules will also be produced in the radiolysis, there is considerable evidence to support the view that their modes... 

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