Quadricyclane hydration kinetics in natural waters

Hydration rates of quadricyclane were measured over a pH range of 3 to 8 in phosphate buffer, carbonate buffer, and nitric acid solutions. Norbornadie ne was a minor impurity in the quadricyclane, and its hydration rate was al so measured. Hydration products were exo-5-norbornen-2-ol (bicyclo[2.2.1]he pt-5-ene-2-ol) and nortricyclyl alcohol (tricyclo[2.2.1.0(3,5)]heptane-2-ol ). Diol formation was not detected. Quadricyclane hydration in solutions co ntaining chloride ions formed the alcohols and their chlorinated analogs. A mechanism consistent with observed kinetics and reaction products involvin g two carbocation intermediates is proposed. Comparison of reaction rates w as used to determine the role of buffer catalysis and chlorination reaction s in natural waters. Phosphate buffer catalysis was shown to be important, and rate constants for all phosphate species were calculated. Comparison of hydration rates in nitric acid and carbonate buffer indicated that catalys is by carbonate species for this reaction is unimportant in surface waters. Catalytic effects of other buffers in some natural waters appear possible. Proper buffer selection is important if laboratory-measured hydration rate s of quadricyclane are to be applied to natural water systems.