Photo-oxidations of hydrogen-bonded phenols using excited-state polyarenes are described to derive fundamental understanding of multiple-site concerted proton-electron transfer reactions (MS-CPET). Experiments have examined phenol bases having -CPh2NH2, -Py, and -CH2Py groups ortho to the phenol hydroxyl group and tert-butyl groups in the 4,6-positions for stability (HOAr-NH2, HOAr-Py, and HOAr-CH2Py, respectively; Py = pyridyl; Ph = phenyl). The photo-oxidations proceed by intramolecular proton transfer from the phenol to the pendent base concerted with electron transfer to the excited polyarene. For comparison, 2,4,6-(Bu3C6H2OH)-Bu-t, a phenol without a pendent base and tert-butyl groups in the 2,4,6-positions, has also been examined. Many of these bimolecular reactions are fast, with rate constants near the diffusion limit. Combining the photochemical k(CPET) values with those from prior thermal stopped-flow kinetic studies gives data sets for the oxidations of HOAr-NH2 and HOAr-CH2Py that span over 10(7) in k(CPET) and nearly 0.9 eV in driving force (Delta G degrees'). Plots of log(k(CPET)) vs Delta G degrees', including both excited-state anthracenes and ground state aminium radical cations, define a single Marcus parabola in each case. These two data sets are thus well described by semiclassical Marcus theory, providing a strong validation of the use of this theory for MS-CPET. The parabolas give lambda(CPET) congruent to 1.15-1.2 eV and H-ab congruent to 20-30 cm(-1). These experiments represent the most direct measurements of H-ab for MS-CPET reactions to date. Although rate constants are available only up to the diffusion limit, the parabolas clearly peak well below the adiabatic limit of ca. 6 X 10(12) s(-1). Thus, this is a very clear demonstration that the reactions are nonadiabatic. The nonadiabatic character slows the reactions by a factor of similar to 45. Results for the oxidation of HOAr-Py, in which the phenol and base are conjugated, and for oxidation of 2,4,6-tBu(3)C(6)H(2)OH, which lacks a base, show that both have substantially lower lambda and larger pre-exponential terms. The implications of these results for MS-CPET reactions are discussed.