Four quick calculators for organic chemistry — molecular weight and unsaturation from a formula, stoichiometry, an acid–base equilibrium predictor, and a reagent finder — all running in the browser.
Molecular weight, percent composition, and degrees of unsaturation from a formula
Stoichiometry: percent yield, molarity, and dilution
Acid–base equilibrium predictor (direction and Keq from pKa)
Reagent finder by role, with conditions and common sources