Ionization potential minimum values

The minimum energy I required for ionization is called the (first) ionization potential. The W value is the average energy required to produce a pair of ions in the medium. Experimentally this value is obtained by dividing the absorbed dose by the total number of collected ions. The W value depends primarily on... 

The orbital energies form the well-known HF energy bands, where n is the band index. According to Koopmans theorem [43], the band energies for the occupied bands i and unoccupied bands a, are equal to the corresponding ionization potentials and electron affinities, respectively. When (aka) and (zk,) are the lowest unoccupied and the highest occupied orbitals, respectively, A HF(ikt ak ) reaches its minimum. This minimum value is called the HF band gap. Let us denote it as E F. 

According to the data presented, the value of the ionization potential (IP) for the transition states is correlated with the activation eneigy and increases as the number of alkyl substituents at the double bond grows. For ethylene of the transition state Ic the IP value amounts to 12.28 eV whereas this value of butane-2 is already 12.28 eV. The exception is the isobutylene the IP and A Gt 298 values of which are minimum in the considered alkene series. It is probably e qilained by F effect of two methyl substituents leading to a considerate distortion in electronic density of the double bond. 

Rate constants ( 2) for cycloadditions of phenyl azide to substituted ethylenes and acetylenes stretch over seven magnirndes high values were observed for enamines, moderate k2 for the acrylic ester type, and the rate minimum was found for common alkenes and alkynes (Huisgen, Szeimies, Mobius, 1967). hi the PMO treatment of concerted cycloadditions, Reiner Sustmann found the key to the understanding of substituent effects e.g., a plot of k2 for the cycloadditions of Ph-Ns versus the ionization potential of substituted ethylenes and acetylenes furnished a degenerate U shape (1971). Such a plot is a distinguishing feature for each 1,3-dipole and reflects the specific mix of nucleophilic and electrophilic activity, modified by steric effects. 

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