Ethane ionization potential

In the cyclophane 1, although the overlap between the n-system (2p) and the bridging cr-bonds (2s2p) is most effective, these orbital energy levels match worst, the first ionization potentials being 9.25 eV for benzene and 12.1 eV for ethane. As a result, the HOMOs are the almost pure it MOs with the b2g and b3g combinations. Both the PE spectrum and theoretical calculation demonstrate the degeneracy of the two HOMO levels. The absorption bands are attributed to the 17-17 transitions associated with the HOMOs. 

Fig. 23. Adiabatic ionization potentials for methane, ethane, propane, and butane arranged as an energy level diagram.

Fig. 5. Rate of H—D exchange versus ionization potential of alkanes and aromatic compounds 1 = methane 2 = ethane 3 = propane 4 = n-butane 5 = n-pentane 6 = n-hexane 7 = cyclopentane 8 = cyclohexane 9 = benzene 10 = naphthalene 11 = phenanthrene 12 = 2,2-dimethylbutane (see text) 13 = 1,1-dimethylpropy I benzene (see text) 14 = 2-methylpropane 15 = 2-methylbutane 16 = 2,2-dimethylpropane 17 = 2-methylpentane 18 = 3-methylpentane 19 = 2,3-dimethylbutane 20 = 2,2-dimethylbutane.

The best estimates have been obtained to date by using the MINDO and PNDO methods. In Tables 6 to 8 we show the ionization potential values obtained by each of these methods for alkanes and cycloalkanes, alkenes, acetylenes and aromatic compounds. Dewar and Klopman (PNDO) and Dewar et al. (MINDO/2) also compared their calculated inner orbital energies with experimental ionization potentials obtained from photoionization spectra. The ionization potentials of methane and ethane have also been calculated by the PNDO method along the more sophisticated procedure of minimizing separately the energy of the ion and that of the molecule. In these cases, the experimental value of the first ionization potential was reproduced accurately 48>. 

Our intuition derived from the per and 7r-fluoro effects suggests that fluorination of the nonplanar ethane should be accompanied by an increased ionization potential. Reference 3 corroborates this C2H6 and C2F6 have ionization potentials of 11.52 and 13.4 eV respectively. Likewise, our intuition suggests that the ionization energies of planar CH3 and planar CF3 should be comparable. From the definition of the inversion barrier, AE nv. as the energy difference of the planar and pyramidal forms and the identity for adiabatic ionization potentials (equation 3),... 

The first ionization potential of ethane was measured by photoionization techniques more than 30 years ago [56-62] and it was found to be between 11.4 and 11.65 eV. Some indication of vibrational fine structure was found by Chupka and Berkowitz [62]. The classic Hel photoelectron spectrum of ethane was recorded by liirner s group (Baker et al. [25, 57] it is reproduced on Figure 3. 

The first ionization potential may prove useful in sorting out and ordering the data for binaries of inorganic compounds, but it is certainly of little use in the prediction of ky s for hydrocarbon-hydrocarbon binaries. For example, the I of n-pentane (10.55 eV) is very similar to that of ethylene (10.51 eV), but the kys for the n-pentane binaries are markedly lower than those for the corresponding ethylene binaries (4). On the other hand, the ethylene and ethane binaries have similar kys (Figure 2), even though the I of ethane is 1.25 eV higher than for ethylene (20). 

Hall correlated the ionization potentials of hydrocarbons, ethane to decane, assuming xmchanged localized orbitals and energies c, and y. ... 

Using the indirect method it is not necessary to make the difficult measurement of the ionization potential of the radical, and also the heat of formation of the radical is found more directly. Under the impact of electron bombardment, propane can dissociate into ethyl ions and method radicals. Ethane can dissociate to produce ethyl ions and hydrogen atoms, so that the difference between the energies of these two processes corresponds to that for the reaction between propane and a hydrogen atom to give ethane and a methyl radical. The heats of these processes are< ... 

Most organic compounds except permanent gases, C1-C4 alkanes, methanol, acetonitrile, and chloromethanes Low molecular weight compounds with high ionization potentials (e.g., formaldehyde, ethane, chloromethanes, acetylene, etc.)... 

Grassi et al [25]). Agreement with experimental values is also found for ionization potentials and for electron affinities for several molecules, but the reader is referred to the original paper [25] for further details. There it is noted that the above method could also be applied to the study of the torsional barrier in ethane and to the transition between the two geometries of malonaldehyde [27]. 

Figure 10.5 Effect of the number n of carbons, (a) On the ionization potential of C2-C4 hydrocarbons, = indicates olefin, (b) In the case of ODH, on the differenee of ionization potential AI between reactant and product indicates ODH of C alkane (e.g., C2 for ethane to ethene)...

PF and A for the pure solvent) and will be cancelled out when computing the binding constants or the correlation function. The quantity Eq( ) is essentially the rotational potential energy of the empty molecule, i.e., the doubly ionized acid, as given in Eqs. (4.8.26) V ,(< >) in Eq. (4.8.26) is the rotational potential energy of ethane (Eliel and Wilen, 1994) and is given by... 

The third class of organic donor molecules are a-donors, viz., alkanes and cycloalkanes. These substrates have inherently high ionization and oxidation potentials. Therefore, their radical cations are not readily available by photoinduced electron transfer, but typically require radiolysis and electron impact in the condensed phases or the gas phase, respectively. Thus, radical cations of simple alkanes (methane [206], ethane [207]) or unstrained cycloalkanes (cyclopentane, cyclohexane) [208] were identified and characterized following radiolysis in frozen matrices. In contrast, strained ring compounds have significantly lower oxidation potentials so that the radical cations of appropriate derivatives can be generated by photoinduced electron transfer. 

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