Intermolecular reactions of triplet 2-pentanone with tributyl stannane (TBS) and n-butyraldehyde (BA) were studied in iso-octane. Three types of interactions between the triplet ketone (K) and additives TBS and BA were investigated, namely intermolecular hydrogen abstraction, triplet energy transfer and bimolecular deactivation. The overall quenching efficiencies were found to be high and similar for TBS and BA. However, intermolecular hydrogen abstraction is predominant in the K-TBS system, whereas triplet energy transfer prevails in the K-BA system. From the experimental data, rate constants were derived for the intermolecular primary processes of triplet 2-pentanone. Finally, competitive intramolecular and intermolecular hydrogen abstraction reactions of triplet 2-pentanone were studied and a rate constant for type II decomposition was derived.