The photoreactivity of differently substituted (chloromethoxybenzyl)trimethylsilanes in alcohols and alcohol/water mixtures has been investigated by means of a combined computational and experimental approach. Subsequent elimination of the chloride anion and the trimethylsilyl cation gives the corresponding methoxy-substituted alpha,n-didehydrotoluenes (alpha,n-MeO-DHTs). The rate of desilylation is evaluated through the competition with arylation via phenyl cation (ca. 10(8) s(-1)). alpha,2-MeO- and alpha,4-MeO-DHTs show a purely radical behavior (H abstraction from the solvent methanol), while alpha,3-MeO-DHT, shows mainly a ionic chemistry, as when the parent alpha,3-DHT is thermally generated. This is likely due to triplet-singlet surfaces crossing occurring during desilylation.