AbstractWe have computed surface local ionization energies [ĪS(r)] and electrostatic potential minima (Vmin) for the conjugate bases of a series of cyclic hydrocarbons, using anab initioself‐consistent field–molecular orbital approach. Our ĪS(r) andVminresults are discussed in relation to the acidities of the parent hydrocarbons. A good correlation exists between experimentally determined pKavalues and the lowest surface Ī(r) values [ĪS,min], providing a predictive capability for estimating unknown pKa's. The electrostatic potential minima,Vmin, do not relate as well to pKaas does ĪS,min. Using our ĪS,minversus pKacorrelation, we predict the pKa's of the strained cage polyhedranes cubane, triprismane, and tetrahedrane to be 36, 32, and 26, res