Huckel Analysis

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.

Options

Type
  • 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.
Subtype
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

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

Output Ports

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Output table that contains huckel analysis.

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Installation

To use this node in KNIME, install the extension ChemAxon/Infocom JChem Extensions Feature from the below update site following our NodePit Product and Node Installation Guide:

v5.9

A zipped version of the software site can be downloaded here.

Plugin provider: Infocom Corporation
Plugin version: 4.7.0.v250304
On NodePit since: 2025-12-17
Last update: 2026-01-06
Tags: Streamable
KNIME versions: v5.9, v5.8, v5.7, v5.6, v5.5, v5.4, v5.3, v5.2, v5.1, v4.7, v4.6, v4.5, v4.4, v4.3, v4.2, v4.1, v4.0

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