The rates of the acid-catalyzed hydrolysis of methyl dimethyl-, diethyl-, diisopropyl-, and di-tert-butylphosphinate in D2SO4–D2O and of p-methoxybenzyl, p-chlaorobenzyl, p-nitrobenzyl, and benzyl diethylphosphinate in H2SO4 – 70% w/w DMSO-H2O have been studied. The bell-shaped pH-rate profiles, the Bunnett–Olsen Φ (0.91 to 1.28), Bunnett w (2.28 to 3.52) and w* (−0.94 to +0.17), and Yates-McClelland r (0.61 to 2.6) values, and the entropies of activation (−18 to −24 eu) all support an A2 mechanism for the methyl esters. The suggested mechanism for the benzyl esters is a unimolecular hydrolysis (Aa11). This conclusion is supported by the pH-rate profiles, the Φr values (−0.12 to −0.29) and the entropies of activation (−4 to −7 eu). The pKa's of the esters are also reported and they range between −2.4 to −3.3.
In this study, several unsymmetrical Schiff bases and their cobalt and manganese complexes have been synthesized and characterized. The unsymmetrical Schiff bases were prepared from reaction of o-phenylendiamine derivatives with 1-hydroxy-2-acetonaphthone and then the product was reacted with the following aldehydes: salicyaldehyde, 2-hydroxynaphthaldehyde, 2-pyridinecarboxaldehyde and 2-qinolinecarboxaldehyde to produce the desired tetradentate unsymmetrical Schiff base ligands H2SL, H2NL, HPYL and HQN, respectively. Reaction of these ligands with cobalt and manganese salts produced complexes of the general formula [M(SL)], [(NL)], [M(PYL)] and [M(QL)]. All the complexes were characterized by elemental analysis, infrared spectroscopy, UV-visible spectroscopy, electrical conductivity and magnetic susceptibility measurements. The prepared complexes were examined for their anti-bacterial activity using gram-positive and gram-negative pathogens. The following complexes showed strong antibacterial activity against Staphylococcus aureus: MnSL1, MnSL2 and MnSL3. The genotoxic activity of four complexes, which are MnNL1, MnSL1, CoNL1 and CoSL1, were examined using 8-hydroxy-2-deoxy guanosine (8-OHdG) assay in cultured human blood lymphocytes. All examined complexes were found to be genotoxic at examined concentrations (0.1-100 µg/mL), but with variable magnitudes (p < 0.05). The levels of 8-OHdG induced by MnNL1 and MnSL1 were significantly higher than that induced by CoNL1 and CoSL1 ones. In general, the order of mutagenicity of the compounds is MnSL1 > MnNL1 > CoSL1 > CoNL1. In conclusion, some of the prepared complexes showed some biological activities that might be of interest for future research.
The rate of the oxidation of triethylamine by ferricyanide ions in sodium hydroxide or potassium hydroxide solutions has been determined spectrophotometrically at 25℃. Analysis of the kinetic data indicates that the hydroxide ion does not appear in the rate law. Strong retardation of the oxidation of triethylamine, caused by the addition of ferrocyanide ions, has been observed. A plausible mechanism is suggested, and a suitable rate law, congruent with the experimental observations, has been derived.
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