Highest occupied molecular orbital HOMO energy

The second characteristic center of reactivity within phosphaal-kenes is the (p-p)-n bond. The reactivity is more similar to the C=C than to the corresponding C=N or P=N double bond. This is in accordance with the highest occupied molecular orbital (HOMO) energy levels of the phosphaalkenes, which frequently are n orbitals, as with olefins (51). The olefinic character is also demonstrated by the lower polarity of the P—C bond in comparison with the C—N or P—N bond. 

The highest occupied molecular orbital (HOMO) energy of the cis- and /ra r-isomers of dibenzodioxadiselenaful-valene 3 were calculated at the B3LYP/6-311+G(2d,p) level <2004JOC9319>. 

The standard potentials f/R,oo, which hold for Oox = red in Eq. (21) or y = 1/2 in Eq. (22), depend directly on the chemical nature of the compound. Consequently, they are linked to the corresponding electronic energy levels derived from the molecular orbital (MO) theory. A linear dependency between [/r,oo and the corresponding eigenvalue coefficients for the lowest unoccupied molecular orbital (LUMO) or highest occupied molecular orbital (HOMO) energy levels was found... 

Methods other than thermodynamic cycles are often used to calculate acid dissociation constants. Previous publications implement the theoretical relationship between pKa and structural property [6], bond valence methods and bond lengths [33], pKa correlations with highest occupied molecular orbital (HOMO) energies and frontier molecular orbitals [34], and artificial neural networks [35] to predict pKa values. In addition much work has been done using physical properties as quantitative structure-activity relationship (QSAR) descriptors, and regression equations with such descriptors to yield accurate pKa values for specific classes of molecules [36-47]. The correlation of pKas to various molecular properties, however, is often restricted to specific classes of compounds, and it is... 

Table III. Highest Occupied Molecular Orbital (HOMO) Energies, Mulliken Charges, g0> and Calculated and Experimental Proton and Methyl Cation Affinities of Some Oxyanions...

Energy Calculations. Because cinnoline is insufficiently stable for experimental study, the total and bond separation energies for cinnoline have been calculated for comparison with those of related heterocycles. Highest occupied molecular orbital (HOMO) energies have been used to calculate pXa values for cinnoline and other benzodiazines. ... 

As early as 1979, Catalan and Macias demonstrated linear relationships between the gas-phase acidities of monosubstituted phenols and benzoic acids and a variety of molecular indices calculated by Intermediate Neglect of Differential Overlap (INDO) and ab initio methods [171]. Among these indices the calculated energy difference AE = E(AH) -E(A ) provided especially good linear relationships with the acidities. La Manna, Tschinke, and Paoloni reported a linear relationship between the gas-phase acidities of substituted benzoic acids and the highest occupied molecular orbital (HOMO) energies of the corresponding anions [227]. 

In 1995 Soscun Machado and Hinchliffe [373] used Hartree-Fock 6-31G and 6-31G calculations to estimate the pK s of a set of mono cyclic and bicyclic azines. For three classes (see representatives below) they found good correlations (r = 0.91-0.99) between the energies of the highest occupied molecular orbital (HOMO) energies enoMo the pK s. 

As mentioned, the applications of chiral secondary amines in domino processes have been numerous, mainly because of the dual mechanism of activation allowing easy incorporation of other reactions [7, 8]. The first of these processes involves an iminium-enarnine (Scheme 7.1a), and the second an enamine-iminium activation (Scheme 7.1b), both of which can be in operation in domino reactions involving Michael reactions. These modes of action rely on the lower energy lowest unoccupied molecular orbital (LUMO) for the iminium ion and a rise in the highest occupied molecular orbital (HOMO) energy for enamine activation, which are discussed in further detail in Chapter 10 of this book [9, 10]. In the... 

The calculated singlet-triplet gap for 20 is 17.0 kcal moP compared to a value of 51.8 kcal mol for CH2=C=0, and the smaller gap for 20 arises from an increase in the (highest occupied molecular orbital) HOMO energy, whereas there is Httle effect on the (lowest unoccupied molecular orbital) LUMO. The X-ray stmcture for 20 shows a long bond between the N... 

Table 1.1 summarizes the geometrical parameters, total energies, binding energies (BEs), and highest occupied molecular orbital (HOMO) energy. From Table 1.1 it is... 

---