Specific influence of salts on the hydrolysis reaction rate of p-nitrophenyl anthranilate in binary acetonitrile–water solvents

Spectrofluorometric investigations on the solvent effects on the photocyclization reaction of diclofenac

The solvent effects on the photochemical conversion rate of the photosensitizing drug diclofenac (DCF) were investigated using steady-state fluorescence spectroscopy. The spectral information obtained for the photochemical reaction of DCF in a set of neat solvents demonstrates that the photoconversion reaction rate of DCF is not only medium polarity dependent but also hydrogen-bonding dependent. The solvent effects were qualitatively and quantitatively assessed employing various solvatochromic models, including multi-parameter linear regression analysis (MLRA). Interestingly, the MLRA results (R = 0.99) revealed that the photoconversion rate increases with increasing solvent polarizability (π*) and H-bond donor capability (α), whereas the rate decreases with increasing hydrogen-bond acceptor capability (β). However, predominant effect of the solvent acidity compared to basicity and polarizability was observed. A hypothesis rationalizing the effects of H-bonding and medium polarity on DCF photoconversion reaction is presented and discussed.

Dilute nitric or nitrous acid solution containing halide ions as effective media for pure gold dissolution

Bromide salts are more effective than chloride salts in gaining the ability of dissolving gold in dilute aqueous nitric acid solution. At 60 °C, a piece of gold-wire (ca. 20 mg) is dissolved in 20 mL of as low as 0.10 mol L⁻¹ HNO₃ solution containing 1.0–5.0 mol L⁻¹ NaBr and the dissolution rate constant, log(k/s⁻¹), increases linearly with increasing NaBr concentration.