A detailed analysis of the global and local reactivity patterns of neutral and charged peroxides, including hydrogen peroxide (HOOH), peroxynitric acid (HOONO2), the peroxymonocarbonic ion (HOOCO2-), and the peroxymonosulfate ion (HOOSO3-) in the presence of a polar solvent (water) is presented. The polar solvent effects are included using an isodensity surface polarized continuum model (IPCM). The (1,2) hydrogen-shift reaction for these peroxides is studied. The transition states involved in the (1,2) hydrogen shift have been located and characterized at the B3LYP/6-311G** level of theory. The global analysis shows that, although the replacement of one hydrogen atom in HOOH by a neutral NO2 group enhances both the global softness and global electrophilicity, the substitution of one hydrogen atom by charged CO2- and SO3- groups results in a significant electrophilic deactivation of HOOCO2- and a moderate electrophilic activation of HOOSO3- This result is observed in both the ground state and in some activated forms involved in the (1,2) hydrogen rearrangement. The local analysis, however, shows that the transition-state structures for the same rearrangement of HOOH and the HOOCO2- ion display an electrophilicity-enhanced pattern at the oxygen atom that is being deprotonated, thereby suggesting that this activated form is more likely to be involved in the oxygen-transfer reactions. The site-activation analysis performed on the basis of the variations in local softness from the ground to the transition states is also consistent with this local reactivity picture.