Current Physical Chemistry - Volume 8, Issue 1, 2018

Objective: Storage time without use (STWU) in the supporting electrolyte solution for time periods beyond 30 hours deactivates poly(o-aminophenol) (POAP) films. Observations: Deactivated POAP films exhibit a lower conductivity than freshly prepared (nondeactivated) films Considering the interest in POAP synthesized in acid medium in both basic and applied research, not much attention has been paid to the decay of the electroactivity of POAP caused by its extensive use. Conclusion: Deactivation of poly(o-aminophenol) (POAP) film electrodes by STWU in the supporting electrolyte solution is reviewed in this work.

Background: Synthetic dyes have attracted significant attention in the leather tanning, textile, paper and pulp as well as in the food industry. As most of the synthetic dyes are nonecofriendly, numerous methods have been devised to treat such water in low cost. Oxidation kinetics of food dye i.e. Quinoline Yellow (QY) by Chloramine-T (CAT) in both acidic and alkaline media has been investigated using conventional spectrophotometric technique. Method: The experimental rate law was found to be –d[CAT]/dt = k[QY][CAT]1[H+]y[PTS]-Z, –d[CAT]/dt= k[QY][CAT]1[OH-]-y[PTS]-Z in acid and alkaline medium, respectively. Result: Increasing ionic strength had no effect on the rate of the reaction and also the solvent isotopic effect was examined. The dielectric effect and reduction product, ptoluenesulphonamide (PTS) was negative. The reaction was studied at different temperatures and the activation parameters were computed. The result of this study helped in deducing the plausible mechanism and rate law.

Aim: The kinetics and mechanism of Ruthenium catalysed oxidation of Esmolol by Cerium(IV) sulphate in aqueous H2SO4 at a constant ionic strength of 0.50 mol dm-3 was studied spectrophotometrically. Observation: The reaction showed first order kinetics in both Cerium(IV) and Ruthenium(III) whereas fractional order in Esmolol. Addition of products showed no effect on the rate of the reaction. The main product, methyl-3-(4-(2-hydroxy-3-oxopropoxy) phenyl) propanoate, was identified with the aid of IR and Mass Spectral data. Stoichiometry with respect to the drug substrate and reagent was established as 2:1. Added H2SO4, SO4 2- and HSO4- showed negligible influence on the rate of the reaction in the specified concentration limits. HCe(SO4)3-was found to be the predominant reactive species under the specified experimental conditions. Conclusion: The rate constants (k), catalytic constant (kc) and equilibrium constant (K6) for the proposed mechanism were determined. The kinetic and thermodynamic activation parameters were computed for both the slow rate determining step and complex forming equilibrium step. The catalyst exerted its influence by forming a complex with the drug substrate through metal-substrate bonding in the pre-rate determining step.

Background: Methionine, Met, is one of the sulfur containing amino acids required in the human body by certain biochemical reactions. Since Met is not biosynthesized in humans, it needs to be supplied externally in diet. Met is highly susceptible to oxidation. Objective: The oxidation of Met to its sulfone by CAB in aqueous perchloric acid medium at 323 K has been kinetically studied. Method: Effect of varying ionic strength, solvent composition, dielectric constant has been determined. Effect of reduction product of Chloramine-B (CAB), benzenesulfonamide, on the reaction rate has also been investigated. Conclusion: The experimental rate law obtained is: rate = k#128; [CAB] [H2O]. Activation parameters have been evaluated using Arrhenius and Eyring plots. A mechanism consistent with the observed kinetic data has been discussed. A rate law has been derived based on the mechanism.

Background: The study of various physical behavior of macromolecules in solution is important in understanding the mechanism of transport process. Therefore, our keen intreset to study of various physical parameters of Cu (II) surfactants in benzene a non –polar solvent. Objective: The present work deals with the study of density, molar volume, apprent molar volume of copper surfactants derived from mustard oil in a binary system. Method: Complexes derived from mustard oil with urea / thiourea / 2-amino-6-chloro benzothiazole ligand were synthesized. The synthesized complexes were characterized by elemental analysis, melting points and their IR, NMR and ESR spectral studies. Results: The results were used to determine the critical micelle concentration (CMC), various interactions and the effect of chain length of the soap molecule in non- aqueous, non- polar solvent. The CMC values are found to decrease with increase in average molecular weight of the soap complexes. The apparent molar volume has been examined in terms of Masson equation. Conclusion: This study helps in interpretation of solute solvent interactions, structural insight of micelle and colloidal chemical behavior in binary systems. Study of these factors is essential as it indirectly makes them responsible for their immense applicability in wide areas of field.

Background: The vibronic structures of the first electronically excited state (S1) and ionic ground state (D0) of 2-, 3- and 4-picoline were investigated by means of resonance enhanced multi photon ionization (REMPI) and mass analyzed threshold ionization (MATI) spectroscopy. Objective: The experimental results were supported by geometry optimizations and frequency analyses at the (time-dependent) density functional theory ((TD)DFT) level of theory. Furthermore, the (TD)DFT results were used to calculate the vibrational intensities in the REMPI and MATI spectra by a multidimensional Franck-Condon approach. Method: The experimental data and theoretical predictions matched well for 2- and 4-picoline whereas deviations were observed in the case of 3-picoline. The latter was attributed to a vibronic coupling of the S1 state (1π*←n) to a higher lying 1π*←π state, which is likely to occur for all picolines with 3-picoline exhibiting the strongest coupling. The S1 excitation energies of 2-, 3- and 4-picoline were determined to be 34766 ± 3 cm-1 (4.3104 ± 0.0004 eV), 34660 ± 3 cm-1 (4.2973 ± 0.0004 eV) and 35177 ± 4 cm-1 (4.3614 ± 0.0005 eV) respectively. Results: They are in excellent agreement with the literature. The MATI spectra yielded an adiabatic ionization energy of 72371 ± 5 cm-1 (8.9729 ± 0.0006 eV), 72613 ± 5 cm-1 (9.0029 ± 0.0006 eV) and 72932 ± 4 cm-1 (9.0424 ± 0.0005 eV) for 2-, 3- and 4-picoline respectively. Conclusions: These are the most accurate values reported to this day. In addition, the geometry and vibronic structure of the first electronically excited state and ionic ground state have been determined.