The investigation of proton exchange dynamics at carbon atoms has been so far limited to molecules activated by an electron-withdrawing substituent or by the removal of one electron yielding the corresponding cation radical. A method is proposed to overcome this limitation and extend the gathering of data to nonactivated carbon acids, RH. It consists of using photoinjected electrons to generate the radical R. from a rapidly or concertedly cleaving substrate, RX. The variations of the radical "polarogram" (in which R. is converted into R-) upon addition of an acid are then exploited to derive the protonation rate constant of R-. The method is demonstrated with the example of the diphenylmethyl carbanion. The Brönsted plot thus obtained indicates that proton transfer to this carbanion is intrinsically slow, with a barrier on the order of 1 eV. An inverted region behavior seems to appear at large driving forces.