The oxidation of 3,3′-dimethoxy benzidine with potassium bromate in acidic solutions

The kinetics and mechanism of the oxidation of 3,3′-dimethoxybenzidine (oda, o-dianisidine) by potassium bromate in aqueous acidic medium were studied by monitoring the formation rate of the reaction product, 3,3′-dimethoxy 4,4′-diphenoquinone at 447 nm. The reaction is, first order with respect to both the substrate and oxidant, and second order with respect to H⁺. The oda: bromate stoichiometric ratio is 1:1. Plausible mechanism and rate laws are proposed accounting the experimental findings. Computer simulations were done using the proposed mechanism.     

Studies on the molybdenum catalysed reaction between toluidine blue and stannous chloride

Summary The detailed kinetics of the reaction between toluidine blue (tolonium chloride) (TB⁺) and stannous chloride in acidic solution catalysed by Mo(VI) are studied. 1,10-phenanthroline activated the reaction. The scope of the reaction as indicator reaction, for the catalytic determination of molybdenum was explored. The effect of various interfering cations and anions on the method were investigated and optimum conditions for analysis of low concentrations of Mo (10^–6 mol/l range) are described. Limitations of the method and alternatives for overcoming the interferences are discussed.     

Bi2O3/FAp,a sustainable catalyst for synthesis of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives through green strategy

The bismuth loaded on fluorapatite (Bi₂O₃/FAp) proved to be an excellent catalyst for the synthesis of novel dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives via a three-component reaction involving the mixture of 1H-1,2,4-triazol-5-amine, ethyl cyanoacetate or ethyl acetoacetate, and different benzaldehydes in ethanol at room temperature. The catalyst material was characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The efficacy of Bi₂O₃/FAp as a heterogeneous catalyst was evaluated with the loading of different wt% of bismuth on FAp. The 2.5% bismuth on FAp performed extremely well as a catalyst with a high yield of products (92%–96%) in a short reaction time (25–35 min). The catalyst was recovered by simple filtration. It showed undiminished activity up to five runs. Simple work-up, room temperature reaction, short reaction time, high yields, no column chromatography, and good reusability of catalyst are the merits of the proposed protocol. In addition, this process offers 100% carbon efficiency and 98% atom economy with noteworthy fiscal and environmental benefits.     

Stability‐indicating HPLC method for simultaneous quantification of 14 impurities in excedrin tablet formulations and identification of new impurity by LC–MS in accelerated stability studies

We developed novel stability‐indicating HPLC method for simultaneous estimation of 14 impurities in excedrin tablet, a formulation with a combination of acetaminophen, aspirin, and caffeine. In addition, a new impurity that was generated through degradation of aspirin at high temperatures during the accelerated stability conditions was positively identified and confirmed, using liquid chromatography–mass spectrometry technique. The HPLC method was optimized using the Inertsustain C₁₈, 250 × 4.6 mm, 5.0 μm column, employing simple gradient method. Forced degradation studies were performed under acidic, basic, oxidative and thermal conditions to prove the scope and stability‐indicating the nature of the method. The optimized method was validated as per the International Conference on Harmonization guidelines. The HPLC method showed linearity from LOQ concentration to 21 μg mL^?1. Precision and intermediate precision values were <5% RSD. The validated HPLC method is currently applied for the routine testing of excedrin tablet formulations in quality control laboratories.     

One-pot green synthesis of novel 5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine derivatives with eco-friendly biodegradable eggshell powder as efficacious catalyst

Research on Chemical Intermediates - An eco-friendly and efficient green protocol is developed for the synthesis of sixteen&nbsp;pyrazolo-phthalazine derivatives (5a–p) by using...     

Overtone spectroscopy of some benzaldehyde derivatives

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm⁻¹ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted benzenes it is only 80% of the para-substituted shift.     

A kinetic study of the reduction of toluidine blue with thiourea in acidic solution

A detailed kinetic study of the reaction of toluidine blue (tolonium chloride) (TB⁺ Cl^?) with thiourea (TU) in aqueous hydrochloric acid solution is reported. The reaction was first order with respect to toluidine blue and the reductant and second order with respect to [H⁺]. Thiourea had a 2:1 stoichiometric ratio with TB⁺. Toluidine blue was reduced to a colorless base in two one-electron reduction steps and TU was oxidized to thioformamidinium ion, which dimerized rapidly to give stable dithioformamidinium ion. The energy parameters obtained for TB⁺-TU reaction were mean energy of activation (Ea′) = 26.7 ± 2.4 kJ M^?1; enthalpy of activation (ΔH^#) = 24.2 kJ M^?1; frequency factor (A) = 1.04 × 10⁴ M^?3 s^?1; and entropy of activation (ΔS^#) = ?176.35 J M^?1 s^?1. © John Wiley & Sons, Inc.     

Ozone initiated oxidation of long chained n -alkanes in the presence of activated charcoal or silica gel

Photolysis behavior of acetamiprid in different kinds of surfactant solutions were investigated. The results showed that acetamiprid was prone to photolysis when exposed to the irradiation of a mercury lamp, and the photolysis kinetics fit in well with the first-order kinetic equation. Surfactants did not participate in the acetamiprid’s photolysis process directly, whereas they all had obvious inhibiting effects on it.