Aniline-co-o-anthranilic Acid Copolymer-Chitosan/Ag@AgCl Nanohybrid as a Carrier for (E)-N'-(Pyridin-2-ylmethylene) Hydrazinecarbothiohydrazide Release and Antimicrobial Activity.

Poly(aniline-co-o-anthranilic acid)-chitosan/silver@silver chloride (PAAN-CS/Ag@AgCl) nanohybrids were synthesized using different ratios of Ag@AgCl through a facile one-step process. The presence of CS led to the formation of the nanohybrid structure and prevented the aggregation of the copolymer efficiently. The synthesized nanohybrids were fully characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis. (E)-N'-(Pyridin-2-ylmethylene) hydrazinecarbothiohydrazide I was prepared using thiosemicarbazide and confirmed by 1H-NMR, 13C-NMR, and FTIR analyses. Loading of the azine derivative I using various concentrations at different pH values onto the nanohybrid was followed by UV-vis spectroscopy. Langmuir and Freundlich adsorption isotherm models were used to describe the equilibrium isotherm, and the adsorption followed the Langmuir adsorption isotherm. A pseudo-second-order model was used to describe the kinetic data. A PAAN-CS/Ag@AgCl nanohybrid loaded with azine I interestingly showed efficient antimicrobial activity against Escherichia coli and Staphylococcus aureus more than the azine derivative I. The release of azine I at different pH values (2-7.4) was investigated and the kinetics of release were studied using zero-order, first-order, second-order, Higuchi, Hixson-Crowell, and Korsmeyer-Peppas equations.

Effect of alkyl chain length, head group and nature of the surfactant on the hydrolysis of 1,3-benzoxazine-2,4-dione and its derivatives.

The alkaline hydrolysis of carsalam (2H-1,3-benzoxazine-2,4(3H)-dione), denoted as I, and its N-substituted derivatives i.e., N-methyl-1,3-benzoxazine-2,4-dione (II) and N-benzoyl-1,3-benzoxazine-2,4-dione (III) was studied spectrophotometrically at physiological temperature. The rate of hydrolysis was found to be independent on the substrate concentration. In case of I, the reaction was fractional order with respect to [OH(-)] while for II and III, reaction obeyed the first order kinetics. Effect of cationic surfactants with varying hydrophobic chains (cetyltrimethylammonium bromide, CTAB, tetradecyltrimethylammonium bromide, TTAB and dodecyltrimethylammonium bromide, DTAB) and with different head-group (cetyl pyridinium chloride, CPC) and anionic surfactant (sodium dodecyl sulfate, SDS) was also seen on the rate of alkaline hydrolysis of the carsalam and its derivatives. Cationic surfactants first catalyzed the rate of hydrolysis at lower concentrations followed by the inhibition at higher concentrations. The length of the alkyl chain had remarkable effect on the catalytic efficiency of the surfactants. Similarly N-substitution on substrate also increased the catalysis by micelles. The anionic surfactant SDS inhibited the rate of hydrolysis at all of the concentrations studied. The catalysis by cationic micelles followed by inhibition was treated in terms of the pseudophase ion-exchange model, while for the inhibition by SDS micelles the Menger-Portnoy model was used to fit the data. The effect of salts (NaCl, NaBr and (CH(3))(4)NBr) was also seen on the hydrolysis of II and it was found that all salts inhibited the rate of reaction. The inhibition follows the trend NaCl

Micellar effects on the alkaline hydrolysis of isatin and its derivatives.

Herein we have investigated the hydrolysis of 1H-indol-2,3-dione (isatin, I) and its derivatives of different hydrophobicities, viz. N-dimethylaminomethyl indol-2,3-dione (II), N-morpholinomethyl indol-2,3-dione (III), N-pipridinomethyl indol-2,3-dione (IV), N-heptylaminomethyl indol-2,3-dione (V), N-dodecylaminomethyl indol-2,3-dione (VI), N-hexylanilinomethyl indol-2,3-dione (VII), N-decylanilinomethyl indol-2,3-dione (VIII), and N-hexadecylanilinomethyl indol-2,3-dione (IX), in the presence of an excess amount of sodium hydroxide. All the isatin derivatives were synthesized in the laboratory. The progress of the reactions was studied by exploiting UV-visible spectrophotometry. The observed rate constant, k(w), increases linearly on increasing the hydroxide ion concentration, indicating first-order dependence on [OH(-)]. The effects of surfactants, cationic (cetyltrimethylammonium chloride, CTACl), and anionic (sodium dodecyl sulfate, SDS) were also investigated. The rate of reaction increased on increasing the concentration of CTACl and, after reaching a maximum, it started decreasing. Conversely, anionic micelles of SDS inhibited the rate of hydrolysis of isatin and its derivatives. The results of the effect of CTACl were analyzed using a pseudophase ion-exchange model while the inhibition by SDS was analyzed using a simple Menger-Portnoy model. The effects of added salts, such as NaBr, NaCl, and (CH(3))(4)NBr, were also seen on the isatin hydrolysis. It was found that the addition of salts decreased the rate enhancement efficiency of the CTACl.