Chromium-Assisted Oxidations with Sodium Perborate by Phase Transfer Catalysis

Oxidation by sodium perborate of selected alcohols and unsaturated compounds to ketones and acids was achieved at 60–80°C in the presence of catalytic amounts of chromium(VI) oxide and methyltridecylammonium chloride.     

ACTIVATED NITRILES IN HETEROCYCLIC SYNTHESIS: NOVEL SYNTHESIS OF PYRROLO[1,2-c]IMIDAZOLE AND PYRANO[2,3-d]IMIDAZOLE DERIVATIVES

Abstract

Several new pyrrolo[1,2-ylidene ethyl cyanoacetate (lc, d) with each of (2) and (11) afforded the 5-ylidene-2-thiohydantoins (Sa, b), (Wn. b) respectively. Compounds Sn, b react with each of malononitrile and ethyl cyanoacet-ate to give the corresponding pyrroloimidazole derivatives (h,b) and (an, b) respectively. The structure of the isolated products were established by elemental analyse and spectral data studies.     

Quantitative Analysis of Ozone and Nitrogen Oxides Produced by a Low Power Miniaturized Surface Dielectric Barrier Discharge: Effect of Oxygen Content and Humidity Level

Plasma Chemistry and Plasma Processing - This study presented a quantitative evaluation of the performance of a low power miniaturized SDBD source for the production of ozone and nitrogen oxides as...     

Thermodynamics and molecular bases of the interaction of ampicillin and streptomycin at their binding sites of bovine serum albumin

Among the biological parameters of chemotherapeutics, serum albumin binding is a critical factor in determining drug distribution and bioavailability. In this study, the binding properties as well as the interaction of ampicillin and streptomycin at their binding sites of bovine serum albumin (BSA) were investigated. The binding constant varied from 3.2 × 10³ M^?1 at 298 K to 37.5 × 10³ M^?1 at 313 K for ampicillin, and from 10.7 × 10³ M^?1 at 298 K to 3.5 × 10³ M^?1 at 313 K for streptomycin. By increasing the temperature, from 298 to 313 K, the binding affinity decreased by about 11-fold for ampicillin. Conversely, streptomycin showed stronger binding at higher temperature, which is decreased by threefold at 298 K. Interestingly, the affinity of ampicillin with the free BSA was ~4-fold higher than the binding with BSA/streptomycin complex. In contrast, the affinity of streptomycin with the free BSA was ~6-fold lower than the binding with BSA/ampicillin complex. Mutual binding experiments indicate that ampicillin and streptomycin are sharing both of common and different binding sites on BSA. Dissection of the forces of interactions indicated that rigid-body binding was the mode of binding of ampicillin and streptomycin with BSA with minor degree of conformational changes. Both of ampicillin and streptomycin can bind with free BSA. Furthermore, the binding of ampicillin with BSA improves the binding of streptomycin, while the binding of streptomycin with BSA adversely affect the binding of ampicillin.     

Radical/Ion pair formation in the electrochemical reduction of arene sulfenyl chlorides

Important aspects of the electrochemical reduction of a series of substituted arene sulfenyl chlorides are investigated. A striking change is observed in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the arene sulfenyl chloride. With p-substituted phenyl chlorides a "sticky" dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With o-nitropheyl sulfenyl substituted chlorides a stepwise mechanism is observed where through space S...O interactions play an important role stabilizing both the neutral molecules and their reduced forms. Disulfides are generated through a nucleophilic reaction of the two-electron reduction produced anion (arenethiolate) on the parent molecule. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with the gas phase chemical quantum calculations results helped rationalize both the observed change in the ET mechanism and the occurrence of the "sticky dissociative" ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in gas phase. This study shows that despite the low magnitude of in-cage interactions in acetonitrile as compared to in the gas phase, their existence strongly affects the kinetics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents.     

Lysinibacillus Isolate MK212927: A Natural Producer of Allylamine Antifungal ‘Terbinafine’

Resistance to antifungal agents represents a major clinical challenge, leading to high morbidity and mortality rates, especially in immunocompromised patients. In this study, we screened soil bacterial isolates for the capability of producing metabolites with antifungal activities via the cross-streak and agar cup-plate methods. One isolate, coded S6, showed observable antifungal activity against Candida (C.) albicans ATCC 10231 and Aspergillus (A.) niger clinical isolate. This strain was identified using a combined approach of phenotypic and molecular techniques as Lysinibacillus sp. {"type":"entrez-nucleotide","attrs":{"text":"MK212927","term_id":"1520090447"}}MK212927. The purified metabolite displayed fungicidal activity, reserved its activity in a relatively wide range of temperatures (up to 60 °C) and pH values (6–7.8) and was stable in the presence of various enzymes and detergents. As compared to fluconazole, miconazole and Lamisil, the minimum inhibitory concentration of the metabolite that showed 90% inhibition of the growth (MIC₉₀) was equivalent to that of Lamisil, half of miconazole and one fourth of fluconazole. Using different spectroscopic techniques such as FTIR, UV spectroscopy, 1D NMR and 2D NMR techniques, the purified metabolite was identified as terbinafine, an allylamine antifungal agent. It is deemed necessary to note that this is the first report of terbinafine production by Lysinibacillus sp. {"type":"entrez-nucleotide","attrs":{"text":"MK212927","term_id":"1520090447"}}MK212927, a fast-growing microbial source, with relatively high yield and that is subject to potential optimization for industrial production capabilities.     

Capillary electrophoretic analysis of sulfur and cyanicides speciation during cyanidation of gold complex sulfidic ores

A capillary electrophoretic protocol for the separation and quantification of the most important species potentially liberated during the cyanidation of gold sulfide‐rich ores was accomplished in this study. The separation of 11 ions: S₂O₃^2–, Cu(CN)₃^2–, Fe(CN)₆^4–, Fe(CN)₆^3–, SCN^–, Au(CN)₂^–, Ag(CN)₂^–, SO₄^2–, OCN^–, SO₃^2–, and HS^– was achieved using an indirect UV detection method. The robustness of the analytical protocol was tested by analyzing ions speciation during the cyanidation of two gold sulfide‐rich ores. The 1‐h cyanidation of the two ores released up to six complexes into solution: S₂O₃^2–, Cu(CN)₃^2–, SCN^–, Fe(CN)₆^4–, OCN^–, and SO₄^2–. The mineralogy of the ore was found to influence directly the nature and the amount of the dissolved species. Conserving the cyanidation solution for 72 h after sampling resulted in 96% total sulfur recovery. These results allow us to conclude that the analytical protocol developed in this study can become very useful for the optimization of precious‐metals cyanidation plants.     

Regioselective bond cleavage in the dissociative electron transfer to benzyl thiocyanates

The electrochemical reduction of benzyl thiocyanate and p-nitrobenzyl thiocyanate was investigated in acetonitrile at an inert electrode. These two compounds reveal a change in the reductive cleavage mechanism, and more interestingly, they show a clear-cut example of a regioselective bond dissociation. Both phenomena may be understood on the basis of the dissociative ET theory and its extension to the formation/dissociation reactions of radical ions. While the effect of the standard oxidation potential of the leaving group seems to be predominant in understanding the change in the ET mechanism by changing the driving force, the regioselective cleavage is dictated by changes in the intrinsic barrier related to the nature of the substituent on the aryl moiety.     

Vibrational Study of Dipotassium Zinc Bis(Dihydrogendiphosphate) Dihydrate,K2ZN(H2P2O7)2·2H2O

Abstract

Infrared and Raman spectra of dipotassium zinc bis(dihydrogendiphosphate) dihydrate, K₂Zn(H₂P₂O₇)₂ .2H₂O have been collected and interpreted using factor group analysis. Noncoincidence of the Raman and infrared spectra bands confirms a centrosymmetric structure for K₂Zn(H₂P₂O₇)₂ .2H₂O previously investigated by X-ray structural study, as well as the joint appearance of ν_as POP and ν_s POP point to a bent POP configuration.