The reactions of nitronates of ring-substituted phenylnitromethanes and enolates of ring-substituted 1-phenyl-2-propanones with MeOBs gave exclusively the O-methylated and C-methylated products, respectively. DFT calculations suggested that two factors, namely, intrinsic barriers and metal-cation coordination, control the C/O selectivity. The kinetic preference for O-methylation in the reactions of nitronates arises from the intrinsic barriers, which are ca. 10 kcal/mol lower for O-methylation than for C-methylation. The situation is the same for the gas-phase reaction of an enolate, in which the O-methylation is more favorable than the C-methylation. The experimentally observed C-selectivity of enolate reactions in solution is due to the metal-cation coordination, which hinders O-methylation for enolates. The effects of the enolate reactivity and the solvent on the C/O selectivity are also rationalized to arise from the two factors.

The formation reaction of peroxodiphosphate (denoted by PDP and meaning P2O84−, HP2O83− etc.) by the reaction of molecular oxygen (O2) with the phosphinate ion (PH2O2−) was extremely accelerated by irradiation with visible light of aqueous solutions containing the tris(2,2′-bipyridine)ruthenium(II) ion ([Ru(bpy)3]2+). The [Ru(bpy)3]2+ acted as a photocatalyst during the reaction. The reaction mechanism consists of a chain reaction being accompanied by the O2-quenching of a photoexcited ruthenium(II) complex ([Ru(bpy)3]2+*) to make the superoxide (O2−•) and [Ru(bpy)3]3+, followed by the reduction of [Ru(bpy)3]3+ by PH2O2− to make [Ru(bpy)3]2+ and PH2O2•. However, such PDP once formed in the presence of O2 began to decrease with a rate law of -d[PDP]/dt = kobsd[PDP] after the solution was saturated with N2 gas, and when the solution was again saturated with air, the PDP began to increase again with light irradiation and remained constant in the dark. Such behaviors are discussed while presenting the reaction mechanisms.

The chromate (VI) ion HCrO4− at pH 2—4 was not appreciablly reduced by the phosphinate ion PH2O2− in the absence of molecular oxygen (O2), but was reduced in the presence of O2, forming peroxodiphosphate ions (denoted by PDP and meaning all forms of P2O84−, HP2O83− etc.) in much higher concentrations than those of the added chromate(VI). Both the rates of the chromate decay and the PDP formation increased with decreasing pH. When the chromate(VI) ion disappeared completely, PDP formation stopped and its concentration remained constant. However, such PDP once formed in the presence of O2 began to decompose after the solution was saturated with N2 gas; its decomposition ceased again when the solution was again saturated with air. Such behaviors are discussed while presenting the reaction mechanisms.