Factors influencing the mechanism of surfactant catalyzed reaction of vitamin C-ferric chloride hexahydrate system

The kinetics of vitamin C by ferric chloride hexahydrate has been investigated in the aqueous ethanol solution of basic surfactant viz. octadecylamine (ODA) under pseudo-first order conditions. The critical micelle concentration (CMC) of surfactant was determined by surface tension measurement. The effect of pH (2.5–4.5) and temperature (15–35°C) in the presence and absence of surfactant were investigated. Activation parameters, ΔE _a, ΔH ^#, ΔS ^#, ΔG ^≠, for the reaction were calculated by using Arrhenius and Eyring plot. Surface excess concentration (Γ_max), minimum area per surfactant molecule (A _min), average area occupied by each molecule of surfactant (a), surface pressure at the CMC (Π_max), Gibb’s energy of micellization (ΔG _M°), Gibb’s energy of adsorption (ΔG _ad°), were calculated. It was found that the reaction in the presence of surfactant showed faster oxidation rate than the aqueous ethanol solution. Reaction mechanism has been deduced in the presence and absence of surfactant.     

Microbial transformation of dehydroepiandrosterone

Transformation of dehydroepiandrosterone (DHEA) (1) was carried out by a plant pathogen Rhizopus stolonifer, which resulted in the production of seven metabolites. These metabolites were identified as 3beta,17beta-dihydroxyanandrost-5-ene (2), 3beta,17beta-dihydroxyandrost-4ene (3), 17beta-hydroxyandrost-4-ene-3-one (4), 3beta,11-dihydroxyandrost-4-ene-17-one (5), 3beta,7alpha-dihydroandrost-5-ene-17-one (6), 3A,7alpha,17beta-trihydroxyandrost-5-ene (7) and 11beta-hydroxyandrost-4,6-diene-3,17-dione (8). The structures of the transformed products were determined by the spectroscopic techniques.     

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.]     

Experimental and Molecular Mechanical Studies of Complexation of Some 2H- and 3H- Indole Derivatives with Aqueous β-Cyclodextrin

Phase solubility diagrams (PSDs) at 25 ^∘C and molecular mechanical (MM) modeling were used to study the aqueous complexation of some 2H- and 3H-indole derivatives with β-cyclodextrin (β-CD). Among the 3H-indole derivatives investigated in this work, indole-3H-butyric acid forms the most stable 1:1 complex of the B _s -type PSD, whereas shorter chain derivatives form soluble 1:1 complexes (A _L -type PSDs) with their stability increasing as the chain length increases. Indole-2 carboxylic acid forms highly stable 1:1 and 1:2 complexes, with the lower-order complex reaching saturation first (B _s -type PSD). MM modeling indicates that the stability of the complex is highly correlated with the flexibility of the 3H-indole hydrocarbon chain, which yields a better geometrical fit within the β-CD cavity resulting from different hydrophilic interactions. These interactions are represented in the H-bonding of the carboxyl group with the primary hydroxyl group network that is situated at the narrow rim of the cavity, and also by a favorable interaction of the aromatic ring with the hydroxyl group network at the other rim.     

First seconds in a building's life-in situ synchrotron X-ray diffraction study of cement hydration on the millisecond timescale

Setting cement: highly dynamic hydration processes that occur during the first seconds of cement hydration were studied by time-resolved synchrotron X-ray diffraction. Polycarboxylate ether additives were found to influence the formation of the initial crystalline hydration products on a molecular level.     

Microbial transformation of oleanolic acid by Fusarium lini and alpha-glucosidase inhibitory activity of its transformed products

The biotransformation of a pentacyclic triterpene, oleanolic acid (1), with Fusarium lini afforded two oxidative metabolites, 2alpha,3beta-dihydroxyolean-12-en-28-oic acid (2), and 2alpha,3beta,11beta-trihydroxyolean-12-en-28-oic acid (3). Metabolite 3 was found to be a new compound. The structures were characterized on the basis of spectroscopic studies. These metabolites exhibited a potent inhibition of alpha-glucosidase enzyme.     

Trans‐ and cis‐ Cobalt(III), Iron(III), and Chromium(III) Complexes Based on α‐ and γ‐Diimine Schiff Base Ligands: Synthesis and Evaluation of the Complexes as Catalysts for Oxidation of L‐Cysteine

The synthesis of a new series of trans and racemic cis isomers of cobalt(III)‐, iron(III)‐, and chromium(III)‐based complexes with the α‐ and γ‐diimine Schiff base ligands, N,N′‐bis(X)‐2,3‐butandiimine and N,N′‐bis(X)‐1,2‐phenyldiimine (X = cyclohexyl, 2‐isopropylphenyl, 1‐naphthyl) is described. To confirm the identity of the complexes prepared in the present study, a variety of techniques including elemental analysis, magnetic susceptibility, infrared‐, mass‐ (EI), and UV/Vis‐ spectroscopy have been utilized. Some of the isolated complexes have been evaluated as catalysts for the oxidation of L‐cysteine. Preliminary results showed that the metal atoms, geometry of the complexes, auxiliary substituents, and the backbone of the ligand influenced the rate of oxidation reaction.