Stabilities of some 2‐( para ‐substituted‐phenyl)‐4,4,5,5‐tetramethyl‐1,3‐dioxolanes relative to their conjugate dioxolenium ions, radicals and carbanions as determined by thermodynamics for hydride and electron transfer in solution

A calorimetric method is described for the determination of the hydride affinities, Δ H   H   −(R + ) of seven dioxolenium ions from the title compounds and also tropylium, trityl and 9‐phenyl xanthylium cations by hydride transfer to the carbocations from BH 3 CN − . Cyclic voltammetric methods yield free energies for reduction of the cations to the conjugate radicals and to the carbanions. The Δ H   H   −(R + ) values correlate well with the first reduction potentials of the cations.