Microdetermination of carbonyl compounds by reduction with alkaline sodium borohydride

Summary Alkaline sodium borohydride has been employed as a reducing reagent for the titrimetric determination of compounds containing the carbonyl function. The sample is dissolved in methanol and is then reduced with alkaline sodium borohydride. After completion of the reaction, the excess sodium borohydride is back titrated against standardized hydrochloric acid solution using methyl red as indicator. The stoichiometry between the carbonyl function and sodium borohydride is 41.

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Zusammenfassung Natriumborhydrid dient als Reduktionsmittel zur Titration von Carbonylverbindungen. Die Probe wird in Methanol gelöst und dann mit alkalischem Natriumborhydrid reduziert. Nach Ablauf der Reaktion wird der Überschuß mit Salzsäure gegen Methylrot zurücktitriert. Carbonylverbindung und Natriumborhydrid reagieren im Verhältnis 41.

     

Small-angle x-ray investigation of a densely packed micelle system in agave hybrid

Small-angle x-ray scattering methods were applied to calculate macromolecular parameters like specific inner surface (O/V), length of coherence (l_c), and the percentage of air present in agave hybrid, treating it as a densely packed colloidal system belonging to a general micelle system. The parameters were equal to O/V = 8.50 × 10^?6 Å^?1, l_c = 150 Å, and the percentage of air = 0.03. The Kratky camera with latest design was used for the experimental measurement. Because the sample agave ybrid is a natural fiber and a highly oriented system that is celluosic in character, the theories of Kratky and Porod have been used to evaluate these parameters.     

Kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium

The kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium has been carried out. The reaction is first order with respect to vanadium(V) and the substrate and is acid catalysed.Hammett acidity function (H ₀) andBunnett hypothesis have been applied. The formation of free radicals during the course of the reaction has been indicated. A probable reaction mechanism is proposed.

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Die Kinetik der Oxidation von Ethyldigol mit Vanadium(V) in wäßrigem saurem Medium

Zusammenfassung Es wurde die Kinetik der Oxidation von Ethyldigol mittels Vanadium(V) in wäßriger saurer Lösung untersucht. Die Reaktion ist erster Ordnung bezüglich Vanadium(V) und Substrat und ist säurekatalysiert. Es wurden dieHammett-Aciditätsfunktion (H ₀) und dieBunnett-Hypothese angewandt. Die Bildung von freien Radikalen während der Reaktion konnte bestätigt werden. Es wird ein Reaktionsmechanismus vorgeschlagen.

     

Retardation of Permanganate-Initiated Polymerization of Acrylonitrile by Phenol

The mechanism and kinetics of the retardation of the permanganate-initiated polymerization of acrylonitrile by phenol have been studied in the temperature range of 30 to 45°C. The effect of monomer, metal ion, phenol, sulfuric acid, organic solvents, and some inorganic salts on the polymerization has been studied. The most remarkable observation in the present investigation was the negative intercept obtained from a plot of [M]/R_p versus 1/[M] of the rate mechanism, This observation appears to be a general phenomenon for all inhibiting substrates. A reaction mechanism has been suggested and a suitable rate law has been proposed.     

Infrared Divergences in Light Front Field Theory and Coherent State Formalism

We discuss fermion self energy correction in light front QED using a coherent state basis. We show that if one uses coherent state basis instead of fock basis to calculate the transition matrix elements the true infrared divergences in δ m ² get canceled up to O(e ⁴). We show this in Light-front as well as in Feynman gauge.     

Ultrasonic and conductometric studies of NaCl solutions and study of ionicity of the liquid solution through the Walden plot and various ultrasonic parameters

Journal of Thermal Analysis and Calorimetry - In this paper, the thermo-physical and hydrodynamic properties of heat transfer nanofluids containing metal nanoparticles-decorated multi-wall carbon...     

Push–Pull Porphyrins via β-Pyrrole Functionalization: Evidence of Excited State Events Leading to High-Potential Charge-Separated States

A new set of free-base and zinc(II)-metallated, β-pyrrole-functionalized unsymmetrical push–pull porphyrins were designed and synthesized via β-mono- and dibrominated tetraphenylporphyrins using Sonogashira cross-coupling reactions. The ability of donors and acceptors on the push–pull porphyrins to produce high-potential charge separated states was investigated. The porphyrins were functionalized at the opposite β,β′-pyrrole positions of porphyrin ring bearing triphenylamine push groups and naphthalimide pull groups. Systematic studies involving optical absorption, steady-state and time-resolved emission revealed existence of intramolecular type interactions both in the ground and excited states. The push–pull nature of the molecular systems was supported by frontier orbitals generated on optimized structures, wherein delocalization of HOMO over the push group and LUMO over the pull group connecting the porphyrin π-system was witnessed. Electrochemical studies were performed to visualize the effect of push and pull groups on the overall redox potentials of the porphyrins. Spectroelectrochemical studies combined with frontier orbitals helped in characterizing the one-electron oxidized and reduced porphyrins. Finally, by performing transient absorption studies in polar benzonitrile, the ability of push–pull porphyrins to produce charge-separated states upon photoexcitation was confirmed and the measured rates were in the range of 10⁹ s⁻¹. The lifetime of the final charge separated state was around 5 ns. This study ascertains the importance of push–pull porphyrins in solar energy conversion and diverse optoelectronic applications, for which high-potential charge-separated states are warranted.     

Evaluation of a Novel Dechlorination Reaction as an Analytically Useful Derivatization Reaction Part 1. Stoichiometry,Mechanism and Yield Optimization

Abstract

A novel reaction for the dechlorination of polychlorinated biphenyls (PCBs) as well as most other chlorinated aromatic and aliphatic compounds is evaluated and discussed in terms of its potential for analytical purposes. The active dechlorinating agent is prepared through the reaction of molten sodium or potassium with polyethylene glycols (MW >200), in the absence of oxygen, to form the corresponding alkali metal glycolate, a powerful nucleophilic agent. Special emphasis is given to the mechanistic aspects of the reaction and their importance in terms of achieving high and reproducible yields with analytical quantities of substrate, in short periods of time. The contribution of the techniques: ESR, NMR, IR, UV, MS, GC-ECD, LC-EC, CIDNP-NMR, conductimetry and chloride analysis (amperometric) in elucidating the reaction mechanism and providing valuable kinetic data is illustrated. This reaction can potentially be applied to the determination of PCBs in waste oils.     

Ni(II) and Cu(II) complexes of bidentate thiosemicarbazone ligand: Synthesis,structural, theoretical,biological studies and molecular modeling

The conventional condensation and refluxing process was employed to synthesize Ni(II) and Cu(II) complexes of Methylcarbamatethiosemicarbazone ligand. Reactions were carried out at the pH of 7. The molar ratio of the ligand and metal salt was 2:1. The structures of the synthesized metal complexes were suggested by different analytical techniques such as magnetic susceptibility, molar conductance, IR, EPR and UV spectroscopy. Experimental studies confirmed the octahedral geometry for all the complexes. The geometry of the ligand and complexes were also confirmed by theoretical studies. The complexes were investigated for biological action against pathogenic fungi (C. krusei, C. albican) and bacteria (S. aureus, E. coli). The antimicrobial results confirmed superior inhibition potential of the metal complexes as compared with the parent ligand. The enhanced antimicrobial activities might be due to the chelation. Molecular-docking assays confirmed the strong interaction of ligand with target antimicrobial protein DNA gyrase-B.