Methane orbital energies

Fig. 1.18. Molecular orbital energy diagram for methane. Energies are in atomic units. ...

FIGURE 3.37 The molecular orbital energy-level diagram for methane and the occupation of the orbitals by the eight valence electrons of the atoms. 

Sander applied DFT (B3LYP) theory to carbenic philicity, computing the electron affinities (EA) and ionization potentials (IP) of the carbenes." " The EA tracks the carbene s electrophilicity (its ability to accept electron density), whereas the IP represents the carbene s nucleophilicity (its ability to donate electron density). This approach parallels the differential orbital energy treatment. Both EA and IP can be calculated for any carbene, so Sander was able to analyze the reactivity of super electrophilic carbenes such as difluorovinylidene (9)" which is sufficiently electrophilic to insert into the C—H bond of methane. It even reacts with the H—H bond of dihydrogen at temperamres as low as 40 K, Scheme 7.2) ... 

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>. 

Calculations were finally performed to investigate a mechanism of the methane production increase by CO2 injection to coal seam. Coal includes carbon, hydrogen, and other elements, as Figure 25.14 depicted a simple model of a coal surface. Figure 25.27 shows a molecular orbital energy level diagram for this... 

Fig. 5. (a) Orbital energies and excitations deduced from the analyzed vibronic spectra of dia-methane. (b) Energies of states and transitions for diazomethane deduced from the spectra, with levels of diazirine for comparison. 

Methane BDE, 76, 113 geometry of, 32 orbital energies, 26 point group of, 6 reaction with methyl radical, 149 total energy, 29... 

This reaction is considered as a model of the catalytic reaction. In this work, CpM(CO)2[B(OR)2] (M=Fe, Ru,or W) was employed as a catalyst. Interestingly, the reaction proceeds through the oxidative addition and the reductive elimination for both methane and benzene in the W complex, where the W(V) complex is involved as an intermediate. On the other hand, the Fe-catalyzed reaction proceeds in one step for both methane and benzene, where the Fe(V) species is not involved as an intermediate but the Fe center takes +V oxidation state in the transition state. Thus, the reaction is considered to be metathesis. In the Ru complex, the reaction proceeds through the Ru(V) intermediate for the C-H o-bond activation of benzene, while it proceeds in one step for the C-H o-bond activation of methane hke that of the Fe complex. The differences among three metals can be interpreted in terms of the d orbital energy and/or the d" d" s promotion energy, as discussed above. 

The nine lowest MOs therefore consist of three and six t2 MOs. The six t2 MOs belong to triply degenerate levels and thus fall into two different shells lt2 and 2 2. Each such shell contains three MOs of equal orbital energy and each shell holds six electrons. SCF MO calculations give the three lowest shells as la, la, and 1 2, with energies -11.20, -0.93, and -0.54 hartrees, respectively. The ground state of methane thus has the closed-shell electron configuration and is a Aj state. 

Fig. 1.10. Molecular orbital energies in atomic units for methane.

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