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Huckel Analysis

StreamableChemAxon/Infocom JChem Extensions version 4.3.0.v202000 by Infocom Corporation

The Hückel Analysis Plugin is able to calculate different structural descriptors for aromatic atoms. Localization energies L(+) and L(-) for electrophilic and nucleophilic attack at an aromatic center are calculated by the Hückel method. A smaller L(+) or L(-) value means more reactive atomic location. Order of atoms in E(+) or in Nu(-) attack are adjusted according to their localization energies. The total π energy, the π electron density and the total electron density are also calculated by Hückel method. Depending on the chemical environment, the following atoms have optimal Coulomb and resonance integral parameters: B, C, N, O, S, F, Cl, Br, I. All other atoms have a default, non-optimized parameter. Theoretical background is taken from Isaacs' book. Additional literature for the Hückel's parameters is Streitwieser's book.


  • HMO E(+)/Nu(-) order: numbers the aromatic atoms according to their probability of being attacked by electrophiles or nucleophiles.
  • HMO Localization energy L(+)/L(-): gives the localization energies of the aromatic center (dimension β).
  • HMO Pi energy: calculates the π energy of the aromatic ring(s) (dimension β).
  • HMO Electron density: calculates the π electron density.
  • HMO Charge density: calculates total charge density on the ring atoms.
  • Localization energy L(+)/L(-): the same as the HMO Localization energy L(+)/L(-), but based on experimental (reaction) data.
  • Electron density: the same as the HMO Electron density, but based on experimental (reaction) data.
  • Charge density: the same as the HMO Charge Density, but based on experimental (reaction) data.
E(+) or Nu(-): for E(+)/Nu(-) order and localization energy L(+)/L(-), the electrophilicity and nucleophilicity approaches can be selected (at least one of them). Results for E(+) are coloured red, and Nu(-) blue.
Take major microspecies at pH
Calculates the values for the major microspecies at the given pH.
Structure column
The structure column.

Input Ports

Input table that contains structure in Structure(Mrv, Sdf, Smiles, etc.) format.

Output Ports

Output table that contains huckel analysis.

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