Photophysical Investigations of Carmoisine Interacting with Conventional Cationic Surfactants Under Different pH Conditions

The present study describes the extent of interactions of an efficient food dye, Carmoisine (CAR), with conventional cationic surfactants, hexadecyltrimethylammonium bromide, and ethylhexadecyldimethylammonium bromide (EHDAB). The study was carried out by quantifying the spectral changes of CAR as a function of premicellar to postmicellar surfactant concentrations at various pH conditions. The quantification of CAR molecules entrapped by cationic micellar systems has been estimated with the help of mathematical models. Binding parameters of each surfactant were calculated using differential spectroscopic method. The enhanced solubilization of dye by switching the pH was observed. In support of the electrostatic forces, the larger and more hydrophobic head group favors the promising solubilization of CAR in the outer region of the micellar interior. These findings extend the proficiency of dye molecule as a reporter for sensing electrostatic environment in lipidic membranes and related organized assemblies.     

Easy preparation of 1,4,5-trisubstituted 5-(2-alkoxy-1,2-dioxoethyl)-1,2,3-triazoles by chemoselective trapping of copper(I)–carbon bond with alkoxalyl chloride

We found that alkoxalyl chloride (ClCOCO₂R) did not carry out an acylation on 1-copper(I) alkyne in solvent without additives, but chemoselectively on 5-copper(I) 1,2,3-triazole (an intermediate in cycloaddition of 1-copper(I) alkyne and azide). Thus, a one-pot preparation of 1,4,5-trisubstituted 5-(2-alkoxy-1,2-dioxoethyl)-1,2,3-triazole was achieved by simply stirring the mixture of 1-copper(I) alkyne, azide, and alkoxalyl chloride at room temperature for 4 h.     

UV-Visible Spectrometric Study and Micellar Enhanced Ultrafiltration of Alizarin Red S Dye

Ultraviolet spectrometric study of alizarin red S (ARS) showed the substantial change in dye spectra by cationic CTAB as compared to anionic SDS and nonionic TX-100 surfactant. High spectral change by CTAB confirms the anionic nature of ARS dye and thus ARS-CTAB complex formation takes place due to electrostatic force of attraction. A little spectral change by SDS is the result of similarly charged repulsive forces that overcome weak hydrophobic-hydrophobic interaction between dye and surfactant micelles. TX-100 exhibited moderate spectral effect responsive to weak hydrophobic-hydrophobic interaction alone. MEUF study of ARS dye justified the spectral changes and dye rejection percentage (R) decreases in the following order: cationic > nonionic > anionic surfactant. Permeate flux (J) slightly decreases in presence of CTAB and it remains virtually constant for both SDS and TX-100. Addition of copper salt (i.e., CuCl₂) in dye-CTAB complex solution, favors rejection (%) removing dye and copper simultaneously via micellar enhanced ultrafiltration.     

FI-spectrophotometric determination of uranium after preconcentration on an anion exchange resin

An economical, fast, sensitive and selective method for the determination of uranium (VI) from sulfate media based on the flow injection on-line preconcentration in a minicolumn having amberlite IRA-402 (strong anion exchange) resin is described. Uranium (VI) was selectively adsorbed on the resin as uranyl trisulfate complex from aqueous solution of pH 2 in the minicolumn (2.56 mm i.d. and 7.5 cm in length) at a flow rate of 10 ml min^?1. The adsorbed uranyl trisulfate complex was eluted by HClO₄ (0.1 mol l^?1, 6.5 ml min^?1) and mixed with arsenazo-III (0.05 %, 6.5 ml min^?1), and passed through the flow through cell of spectrophotometer where its absorbance was measured at 653 nm. Various parameters affecting adsorption and elution of the uranium complex were optimized. For data analyses peak absorbance was used. For 60 and 180 s preconcentration time, enrichment factors (EF) 20 and 40, sampling frequency (SF) 45 and 18 h^?1; and detection limits (DL) (3σ) 14.2 and 8.6 μg l^?1 were obtained, respectively. To enhance the sensitivity of the system, two minicolumns (described above) were used for simultaneous preconcentration and elution purpose. For 60 and 180 s preconcentration time, EF 30 and 50, SF 42 and 17 h^?1 and DL (3σ) 4.4 and 3.44 μg l^?1 were obtained, respectively. The effect of various anions and cations was studied for single column manifold. High selectivity of this method was observed. All the anions and cations studied did not interfere up to 330 times higher mass ratio to 300 μg l^?1 U (VI) except Th(IV) which was tolerated up to 133 times by the addition of washing step in the manifold. The method based on single column manifold was applied on the spiked tap water, biological sample CRM (IAEA-V4) and synthetic leach liquor solution and good recovery was obtained. The method based on dual column manifold was validated on lake sediment SL-1 (CRM) and the results obtained were in good agreement at 95 % confidence level with the given value.     

Historical variations of Bera Lake (Malaysia) sediments geochemistry using radioisotopes and sediment quality indices

The Bera Lake basin is a lacustrine mire system and the largest natural lake in Peninsular Malaysia. Three cores were collected from the lake sediments in order to assess sediment quality and ecological risks for aquatic life and human health. An index analysis approach (C _f , C _d , E _r , and IR) and fallout ²¹⁰Pb and ¹³⁷Cs radioisotopes were applied to assess the impacts of environmental evolutionary changes. Sediment chronology was determined using the Constant Rate of Supply model with the resultant ages verified by ¹³⁷Cs horizons. Although the general contamination factors indicate low risk conditions in Bera Lake the risks associated with individual layers ranged from moderate to considerable. Five deforestation phases can be identified in the dated sediment cores with distinct variations in heavy metal influxes since 1972. These phases are in excellent agreement with the dates of land clearance and development projects undertaken over the past four decades. This study has highlighted the capability of contamination factors and chronological methods in environmental evolutionary studies where catchments have experienced extensive land use changes. The destiny of heavy metal influxes into a lake can also be revealed using this methodology.     

Non-superimposable mirror image crystals of enantiomers by spontaneous resolution and the chiral discrimination mechanism

Non-superimposable mirror image crystals of both enantiomers(S/R) of cyclicγ-alkenyl alcohol(2) have been recognized and remarkably identified by the naked eye.More interestingly,both crystals are an outcome of most astonishingly H-bond and intermolecularσ/π-πinteractions.They accounted for the relatively rare and less predictable spontaneous resolution with optical purity >99%ee from the racemic mixture.The chiral discrimination mechanism of this spontaneous resolution has also been proposed.     

Enantioselective Synthesis and Application to the Allylic Imidate Rearrangement of Amine‐Coordinated Palladacycle Catalysts of Cobalt Sandwich Complexes

The reaction of (η⁵‐(N,N‐dimethylaminomethyl)cyclopentadien‐yl)(η⁴‐tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)‐N‐acetylphenylalanine gave planar chiral palladacycle di‐μ‐chloridebis[(η⁵‐(S_p)‐2‐(N,N‐dimethylaminomethyl)cyclopentadienyl,1‐C,3′‐N)(η⁴‐tetraphenylcyclobutadiene)cobalt]dipalladium [(S_p)‐Me₂‐CAP‐Cl] in 92 % ee and 64 % yield. Enantiopurity (>98 % ee) was achieved by purification of the monomeric (R)‐proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (S_p)‐Me₂‐CAP‐OAc which was applied to asymmetric transcyclopalladation (up to 78 % ee). The (R)‐N‐acetylphenylalanine mediated palladation methodology was applicable also to the corresponding N,N‐diethyl (82 % ee, 39 % yield) and pyrrolidinyl (>98 % ee, 43 % yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(S_p)‐Pyrr‐CAP‐Cl] and AgNO₃ (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (E)‐N‐aryltrifluoroacetimidate (up to 83 % ee), and this catalyst system is also applicable to the rearrangement of a range of (E)‐trichloroacetimidates (up to 99 % ee). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non‐racemic allylic amine derivatives.     

Effect of Nano‐support and Type of Active Metal on Reforming of CH4 with CO2

Two series of Co and Ni based catalysts supported over commercial (ZrO₂, CeO₂, and Al₂O₃) nano supports were investigated for dry reforming of methane. The catalytic activity of both Co and Ni based catalysts were assessed at different reaction temperatures ranging from 500—800 °C; however, for stability the time on stream experiments were conducted at 700 °C for 6 h. Various techniques such as N₂ adsorption‐desorption isotherm, temperature‐programmed reduction (H₂‐TPR), temperature‐programmed desorption (CO₂‐TPD), temperature‐programmed oxidation (TPO), X‐ray diffraction (XRD), thermogravimetric analysis (TGA) were applied for characterization of fresh and spent catalysts. The catalytic activity and stability tests clearly showed that the performance of catalyst is strongly dependent on type of active metal and support. Furthermore, active metal particle size and Lewis basicity are key factors which have significant influence on catalytic performance. The results indicated that Ni supported over nano ZrO₂ exhibited highest activity among all tested catalysts due to its unique properties including thermal stability and reducibility. The minimum carbon deposition and thus relatively stable performance was observed in case of Co‐Al catalyst, since this catalyst has shown highest Lewis basicity.     

Mild,Selective Oxidation of Aromatic Alcohols Using β-Cyclodextrin-Functionalized Glass Microparticles: Characterization,Stability, and Application

The surface of glass microparticle (GMP) was functionalized with β-cyclodextrin (→ GMP-β-CD) and was characterized by x-ray photoelectron spectroscopy (XPS). GMP-β-CD was used to catalyze oxidation of alcohols into aldehydes and katones with excellent yield (86–92%). The modified surface of GMP-β-CD showed no change or degradation after repeated use as confirmed from XPS analysis after 10 cycles.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]