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The rates of the hydrolyses of N-(o-hydroxyphenyl)phthalimide (1) and N-(o-methoxyphenyl)phthalimide (2), studied at different pH, show that the hydrolysis of 1 involves intramolecular general base (IGB) assistance where the o-O- group of ionized 1 acts as IGB and H2O as the reactant. The rate enhancement due to the IGB-assisted reaction of H2O with ionized 1 is>8x10(4)-fold. Pseudo-first-order rate constant for the reaction of water with 2 is approximately 2x10(3)-fold smaller than the first-order rate constant (0.10 s-1) for pH-independent hydrolysis of 1 within the pH range of 9.60-10.10. Second-order rate constants (kOH) for hydroxide ion-assisted hydrolysis of ionized 1 and 2 are 3.0 and 29.1 M-1 s-1, respectively. The solvent deuterium kinetic isotope effect (dKIE) on the rate of alkaline hydrolysis of 1 and 2 reveals that the respective values of kOH/kOD are 0.84 and 0.78, where kOD represents the second-order rate constant for DO--assisted cleavage of these imides (1 and 2). The value of kwH2O/kdD2O is 2.04, with kwH2O and kdD2O representing pseudo-first-order rate constants for the reactions of ionized 1 with H2O and D2O, respectively.

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In this work, TiO2/SiO2 composite photocatalysts were prepared using biogenic silica extracted from bamboo leaves and titanium tetraisopropoxide as a titania precursor via a sol–gel mechanism. A study of the physicochemical properties of materials as a function of their titanium dioxide content was conducted using Fourier transform infrared spectroscopy, a scanning electron microscope, a diffuse reflectance ultraviolet-visible (UV-vis) spectrophotometer, and a gas sorption analyzer. The relationship between physicochemical parameters and photocatalytic performance was evaluated using the methylene blue (MB) photocatalytic degradation process under UV irradiation with and without the addition of H2O2 as an oxidant. The results demonstrated that increasing the TiO2 helps enhance the parameters of specific surface area, the pore volume, and the particle size of titanium dioxide, while the band gap energy reaches a maximum of 3.21 eV for 40% and 60% Ti content. The composites exhibit photocatalytic activity with the MB degradation with increasing photocatalytic efficiency since the composites with 40 and 60% wt. of TiO2 demonstrated the higher degradation rate compared with TiO2 in the presence and absence of H2O2. This higher rate is correlated with the higher specific surface area and band gap energy compared with those of TiO2.