The photochemistry of a series of alkoxyacetophenone derivatives bearing remote phenolic groups has been studied using laser flash photolysis techniques. The compounds are structured with a p- or m-phenolic moiety attached via a m- or p-oxyethyl linkage to the carbonyl chromophore, and each have a lowest triplet state of pi,pi* configuration. The corresponding methoxy-substituted compounds have also been examined. The triplet lifetimes of the phenolic ketones vary with the positions of attachment (meta or para) of the oxyethyl spacer to the carbonyl and phenolic moieties, indicating a very strong dependence of the rate of intramolecular H-abstraction on geometric factors. For example, the: para,para'-linked phenolic ketone has a lifetime tau(T) approximate to 12 ns in dry MeCN solution at room temperature due to rapid intramolecular H-abstraction, while the meta,meta'-derivative exhibits a lifetime tau(T) greater than or equal to 11.5 mu s at infinite dilution and no detectable intramolecular reactivity. The presence of as little as 0.03 M water in the solvent leads to a significant increase in triplet decay rare in ail cases, in contrast to its retarding effect on the rate of bimolecular phenolic H-abstraction in model compounds. Semiempirical (PM3) calculations have been carried out to determine the optimum conformation for abstraction in each molecule as a function of substitution pattern. The variation in the rate constants for intramolecular H-abstraction throughout the series is consistent with a mechanism involving coupled electron/proton transfer within a hydrogen-bonded triplet exciplex, the overall rate of which depends critically on orbital overlap factors between the aromatic rings in the ketone and the phenol.