Electronic Structure Of Ethylene Research Articles

AIM and NPA Studies of the Role of Polarization in Electronic Structures

Atomic charges, as measured by Atoms in Molecule (AIM) or Natural Population Analyses (NPA), of the enolate anions of acetaldehyde and crotonaldehyde and of pentadienyl anion and cation show both charge transfer and polarization effects. In general, normal resonance structures and "curved arrow" symbolism give good representations of π-electron distributions, but back-polarizations in the σ-system complicate these electronic structures and can obscure the correspondence to resonance symbols. Twisting a vinyl group to orthogonality disrupts the π-system, but the vinyl group retains significant charge transfers and polarizations. The role of polarization is also demonstrated by the effect of external positive and negative charges on the electronic structure of ethylene. The π-electronic changes again are straightforward but are changed significantly by σ-polarizations. The polarizability of ethane is about half that of ethylene.

Ethylene. Experimental Evidence for New Assignments of Electronic Transitions in the π → π* Energy Region. Absorption and Magnetic Circular Dichroism Measurements with Synchrotron Radiation

An exploration of the vacuum ultraviolet magnetic circular dichroism and absorption spectra of propylene and a comparison to ethylene spectra provides new information on the electronic structure of ethylene. Ethylene has three electronic transitions in the energy region previously assigned as two. The presently proposed assignments for these transitions are π → 3s(1Ag → 1B3u), π → π*(1Ag → 1B1u), and π → 3p. The lowest energy transition that was previously assigned as the beginning of the π → π* is assigned as the π → 3s transition. The π → π* and π → 3p transitions are accidentally degenerate in ethylene. The electronic transition with sharp structure doublets which was previously assigned as π → 3s is assigned as one of the π → 3p [π → 3pσ (1Ag → 1B2g), π → 3py (1Ag → 1B1g), or π → 3px (1Ag → 1A1g)] vibronically allowed electronic transitions. A case is presented that it is the π → 3pσ (1Ag → 1B2g) and/or the π → 3py (1Ag → 1B1g) electronic transitions that are responsible for the sharp structured doubl...

A semi-empirical theory of the electronic structure of ethylene with particular reference to the ionization potential

The electronic structure of the ethylene molecule is rescrutinized within the framework of the semi-empirical pi-electron theory. The lower electronic energy levels, twisting frequency, ionization potential and electron affinity are calculated without treating the so-called β parameter as empirical. A new approach for calculating the ionization potential is presented, in which an allowance is made for the change in the effective nuclear charge accompanying the actual ionization. The ionization potential is computed to be 10·757 ev, the observed value being 10·62 ev.