Isotope effects in photochemistry.: 1.: o-Nitrobenzyl alcohol derivatives

The photolysis of o-nitrobenzyl alcohol derivatives shows a strong kinetic isotope effect (KIE up to 8.3) at the benzylic center. For some derivatives, the KIE is wavelength dependent, suggesting the involvement of higher excited states. In addition to the important mechanistic consequences, isotopic substitution is a convenient way to alter the quantum yield without changing the absorbance, as would the introduction of substituents. This paves the way for a subtle tuning of the reaction rates in photochemical reactions. We illustrated this feature in the sequential deprotection of a diester protected at both termini with photolabile groups. Copyright © 2004 American Chemical Society.