hall_kier_alpha

skfp.descriptors.hall_kier_alpha(mol: Mol) → float

Hall-Kier alpha index.

Computes the Hall-Kier alpha index [1], which is a measure of molecular flexibility. It is calculated by summing atomic contributions alpha:

\[\alpha = \frac{r}{r(Csp^3)} - 1\]

where:

• r is the covalent radius of the atom

• r(Csp3) is the covalent radius of a sp3 hybridized carbon

Parameters:

mol (RDKit Mol object) – The molecule for which the Hall-Kier alpha index is computed.

References

[1]

Lowell H. Hall, Lemont B. Kier “The Molecular Connectivity Chi Indexes and Kappa Shape Indexes in Structure-Property Modeling” Reviews in Computational Chemistry vol 2 (1991): 367-422.

Examples

>>> from rdkit.Chem import MolFromSmiles
>>> from skfp.descriptors import hall_kier_alpha
>>> mol = MolFromSmiles("C1=CC=CC=C1")  # Benzene
>>> hall_kier_alpha(mol)
-0.78