Descriptors Explained

Visual SmallMol computes standard molecular descriptors for small molecules. All methods are deterministic and citable. Use Molecular Properties to get these values from a SMILES string and download a PDF report; see Data sources for references.

Molecular weight (MW)

Monoisotopic and average mass from IUPAC atomic weights. Same standard used for peptides and small molecules.

logP (partition coefficient)

Octanol–water partition coefficient (log P) estimates lipophilicity. Used in drug-likeness and ADME prediction. Computed from structure using standard algorithms (e.g. fragment-based or atom contribution methods).

TPSA (topological polar surface area)

Topological polar surface area (Å²) is used to predict membrane permeability and oral bioavailability. Based on nitrogen and oxygen surface areas.

Lipinski rule of five

Drug-likeness check: MW ≤ 500, logP ≤ 5, H-bond donors ≤ 5, H-bond acceptors ≤ 10, rotatable bonds (often considered). Used in the Calculator (Lipinski Rule Check) for quick assessment.

Rotatable bonds

Count of single bonds that allow free rotation (excluding terminal groups and rings). High counts can affect oral bioavailability.

Molecular Properties · Data Sources · Docs