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Explore · π-electron model

π electron density and pKa maps

Build a molecule, choose a site and inspect density, charge, potential or orbitals. pH changes the populated states.

Any molecule

Try:

The server builds one RDKit conformer and runs the same orbital layer as the curated set; your browser draws the maps.

Solution mode titrates every ionisable site of the molecule together: each charged group makes it harder for its neighbours to lose a proton (or easier, for opposite charges). Below the map: every step from pH 0 to 14.

Test

Forecast against measured pKa

Read the plot, not a claim. R² and leave-one-out error update for the selected family and descriptor. Hollow points are cases declared outside the π-only model.

Use misses. A systematic miss tells us which omitted interaction is worth testing next.

All values as a table
Model, equations & limits

π density is evaluated from the Löwdin-orthogonalized Hückel density matrix. Atomic and interference terms sum to the same total electron count.

ψk = Σr crk λrorbital
ρ = λTPλπ density
V(r) = ke Σ Qj/|r-rj|electrostatic potential

The lightweight model omits explicit solvent and much σ-inductive physics. Full assumptions, validation and references are kept in π-density docs and pKa validation.