Orbit-transition diagram

Figure 7.9 Electronic transitions in the Bohr model for the hydrogen atom, (a) An energy-level diagram for electronic transitions, (b) An orbit-transition diagram, which accounts for the experimental spectrum. (Note that the orbits shown are schematic. They are not drawn to scale.) (c) The resulting line spectrum on a photographic plate is shown. Note that the lines in the visible region of the spectrum correspond to transitions from higher levels to the n = 2 level.

We have now considered three viewpoints from which thermal electrocyclic processes can be analyzed symmetry characteristics of the frontier orbitals, orbital correlation diagrams, and transition-state aromaticity. All arrive at the same conclusions about stereochemistiy of electrocyclic reactions. Reactions involving 4n + 2 electrons will be disrotatory and involve a Hiickel-type transition state, whereas those involving 4n electrons will be conrotatory and the orbital array will be of the Mobius type. These general principles serve to explain and correlate many specific experimental observations made both before and after the orbital symmetry mles were formulated. We will discuss a few representative examples in the following paragraphs. 

Orbital interaction diagram and EHT calculations show that the 1,2 intramolecular shift of hydrogen is symmetry disfavored [10]. In presence of a transition metal fragment to which the alkyne coordinates, the activation energy is considerably lower. This has been attributed to the tendency of H to shift as a proton rather than as a hydride. 

Fig. 8. Orbital correlation diagram for the addition of methylene to ethylene through transition state a (Pig. 7) 109)...

Zeise s salt, KPtCI3(//2-C2H4), exemplifies transition metal bonding to unsaturated hydrocarbons. The orbital interaction diagram for the T-shaped metal fragment PtClT and... 

Figure 4.89 (a) Orbital energy diagram of a closed-shell molecule (C) and its radical anion, illustrating the much smaller first transition in the latter (R). (b) Absorption spectra of naphthalene and of its radical cation H = HOMO, L = LUMO, S = SO MO (singly occupied molecular orbital)... 

Figure 5 Orbital correlation diagram for the suprafacial [1,3] shift of a proton in propene. The transition-state orbitals are based on the Hiickel orbitals for cyclobutadiene...

Figure 4 Molecular orbital correlation diagram for the ortho addition of benzene to ethene. A plane of symmetry (a) is retained during the transition from benzene plus ethene to bicyclo[4.2.0]octa-2,4-diene.

Fig. 1. Schematic orbital energy diagram representing various types of electronic transitions in octahedral complexes. A line connects an atomic orbital to that molecular orbital in which it has the greatest participation. 1 metal centered (MC) transitions 2 ligand centered (LC) transitions 3a ligand-to-metal charge transfer (LMCT) transitions 3b metal-to-ligand charge transfer (MLCT) transitions...

Fig. 34. Copper d orbital and peroxide n orbital splitting diagram for a copper-peroxide monomer intensity of the charge transfer transition, based on orbital overlap considerations, is indicated by width of the arrows...

A typical example of the three dominant bonding molecular orbitals obtained from the orbital interaction diagram of the cyclopropenylium ring and group 10 (Ni, Pd, Pt) transition metal ML2 unit is shown below. 

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