Ethylene electronic configuration

For some systems a single determinant (SCFcalculation) is insufficient to describe the electronic wave function. For example, square cyclobutadiene and twisted ethylene require at least two configurations to describe their ground states. To allow several configurations to be used, a multi-electron configuration interaction technique has been implemented in HyperChem. 

In terms of Lewis orbitals, the electronic configuration of ethylene can be written as... 

Duncanson (i) of the molecular orbital bonding concepts of Dewar (2), which he developed to explain the structure of Ag+-olefin complexes, led to the suggestion that ethylene is symmetrically coordinated to the metal. Platinum, atomic number 78, has the electronic configuration of the xenon core (Is 2s 2p 35 3p 3d Z = 54), then... 

Figure 7.7 (a) The potential energy of S0, Ti and Si states of ethylene and (b) its electronic configuration, as a function of twist angle during trans-cis isomerization. 

Figure 7.10 An orbital correlation diagram for ethylene dimerization. Left two widely separated ethylene molecules. Center two ethylene molecules close enough for significant interactions to occur. Right cyclobutane electron configurations correspond to the ground state for each stage.

The most common oxidation state of palladium is H-2 which corresponds toa electronic configuration. Compounds have square planar geometry. Other important oxidation states and electronic configurations include 0 ( °), which can have coordination numbers ranging from two to four and is important in catalytic chemistry, and +4 (eft), which is octahedral and much more strongly oxidizing than platinum (IV). The chemistry of palladium is similar to that of platinum, but palladium is between 103 to 5 x 10s more labile (192). A primary industrial application is palladium-catalyzed oxidation of ethylene (see Olefin polymers) to acetaldehyde (qv). Palladium-catalyzed carbon—carbon bond formation is an important organic reaction. 

Let us now apply this method to a specific example. Consider the ethylene molecule with D2h symmetry. As can be seen from the character table of the L 2h point group (Table 6.4.2), this group has eight symmetry species. Hence the molecular orbitals of ethylene must have the symmetry of one of these eight representations. In fact, the ground electronic configuration for ethylene is... 

Molecular orbital computational analysis by PM3 CI UHF semiempirical methods have been used to support the contention that preferable HSOMO-LUMO interactions produce a favored biradical and explain the site selectivity in the sensitized photochemical [2 + 2] cycloadduct formation of 2-pyrones with electron-deficient ethylenes <92BCJ354>. The lowest ionization energies, dipole moment, and dominant electronic configurations of a 5-methylidenated version of 7-nitroso-oxazolo[4,5- ]cyclopenta[e]pyrimidine of unknown origin were calculated by the ADC(3) ab initio method <92CPHii>. An extensive semiempirical and ab initio investigation into the mechanism of oxidation of methanol by PQQ is cited in Section 7.22.12.4. 

The electronic configurations of ethylene and buta-1,3-diene. In both buta-1,3-diene and ethylene, the bonding MOs are filled and the antibonding MOs are vacant. 

Q Show how to construct the molecular orbitals of ethylene, butadiene, and the allylic Problems 15-35 and 36 system. Show the electronic configurations of ethylene, butadiene, and the allyl cation, radical, and anion. 

The mechanism for polymerization of propylene with heterogeneous catalysts is very similar to that of ethylene. Studies with a homogeneous catalyst of a lanthanide element provided early mechanistic evidence. The complex used in these studies was 6.15. In 6.15 lutetium is in a 3+ oxidation state and has the electronic configuration of 4fu. In other words Lu3+ has a full/shell and 6.15 is a diamagnetic complex. 

The electronic configuration of titanium is [Ar] 3d24s2, which means that Ti(IV) compounds are d° species with free coordination sites 1-27,28). H-NMR and 13C-NMR data are known and have been occasionally discussed in terms of bond polarity 19), but such interpretations are obviously of limited value. The electronic structure of methyltitanium trichloride 17 and other reagents have been considered qualitatively 52) and quantitatively S3 56> using molecular orbital procedures. It is problematical to compare these calculations in a quantitative way with those that have been carried out for methyllithium 57> since different methods, basis sets and assumptions are involved, but the extreme polar nature of the C—Li bond does not appear to apply to the C—Ti analog. Several MO calculations of the w-interaction between ethylene and methyltitanium trichloride 17 (models for Ziegler-Natta polymerization) clearly emphasize the role of vacant coordination sites at titanium 58). 

The ground-state configuration of the two-ethylene system is a b u (see Table 7-1). This state is totally symmetric, Ag. The excitation of an electron from the HOMO to the LUMO will give an electron configuration agbiub2u. The direct product is ... 

Ethylene has the well-known classical >2/1 structure with a barrier to rotation. The next in complexity of the simple hydrides is the methyl radical CH3. The obvious (sp2) planar arrangement can only accommodate six of the seven valence electrons. The electronic configuration of this molecule can therefore not be described in terms of either atomic wave functions or hybrid orbitals. An alternative approach is to view the structure of the methyl radical as a reduced-symmetry form, derived from the structure of methane, to be considered next. 

On this basis, let us examine the [4 + 2] cycloaddition of 1,3-butadiene and ethylene, the simplest example of the Diels-Alder reaction. The electronic configurations of these compounds—and of dienes and alkenes in general—have been given in Fig. 29.5 (p. 931) and Fig. 29.6 (p. 932). There are two combinations overlap of the HOMO of butadiene ( 2) with the LUMO of ethylene (tt ) and overlap of the HOMO of ethylene (tt) with the LUMO of butadiene ( 3). In either case, as Fig. 29.20 shows, overlap brings together lobes of the same phase. There is a flow of electrons from HOMO to LUMO, and bonding occurs. 

Appendix 1. The Contributions of Various Electronic Configurations of the MIM model for the State Functions of the PPP model of St3rrene = Benzene(b) + Ethylene(e)... 

Figures are the squares of the coefficients in the state functions expressed as a linear combination of the electronic configurations of the MIM model. GrGround configuration, B Ben-zene, E Ethylene, COOtCarboxyl group. B y, B2u and E- y mean the LE of benzene.

Ethylene has two n electrons. The MO diagram of its n system therefore resembles the MO diagram of the molecule, which has a bonding a, MO and an antibonding MO. The electronic configurations of the molecule... 

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