A Convenient Synthesis of Chiral Oxazolidin-2-Ones and Thiazolidin-2-Ones and an Improved Preparation of Triphosgene

Oxazolidin-2-ones and thiazolidin-2-one are conveniently prepared by condensation of L-serine, L-threonine and L-cysteine, respectively with triphosgene. The corresponding methyl esters may be subsequently obtained by quenching the reaction mixture with methanol, without prior need for the isolation of the free acids. An improved procedure for preparation of triphosgene using an internal cooling system is described.     

Acrylate nanolatex via self‐initiated photopolymerization

The use of UV light to initiate emulsion polymerization processes is generally overlooked, whilst extensive literature exists on photocuring of monomer films. In this study, the unique potential of UV light to produce at ambient temperature polyacrylate latexes without initiator was exploited. Although radical initiators are utilized at low concentration, their cost, toxicity, and odor provide incentives for finding alternatives. Starting with concentrated (30 wt %) and low scattering acrylate miniemulsions (droplet diameter <100 nm), it was demonstrated that acrylate self‐initiation can promote an efficient and fast photopolymerization in micrometer‐scale reactor (spectrophotometric cell) and lab‐scale photoreactor. Herein, all kinetic, colloidal, and mechanistic aspects involved in the self‐initiation of acrylate miniemulsion were extensively examined to provide a complete picture. In particular, the effects of droplet size, initiating wavelength, optical path, and irradiance on the course of the polymerization were thoroughly discussed. A diradical self‐initiation pathway is the most likely mechanism. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1843–1853     

SOME REACTIONS OF ALIPHATIC AMIDES WITH SULFUR AND SODIUM POLYSULFIDES

Abstract

Some reactions of the aliphatic amides, CH₃CONH₂, CH₃CONHCH₃, CH₃CON(CH₃)₂ and CH₃CON(C₂H₅)₂ with elemental S and sodium sulfides, Na₂S _n , n ≥ 1, have been studied. The initial reaction product with elemental sulfur appears to be a substituted polysulfane, CH₃COS _n NR, formed by the insertion of the sulfur chain into the C[sbnd]N bond. This product decomposes on further heating, forming COS as the major gas product. In solutions of Na₂S _n in the amides, the reactive material appears to be elemental S, present in equilibrium with S _n ^?2. In the N-dialkyl substituted amides, CH₃CON(CH₃)₂ and CH₃CON(C₂H₅)₂, the tetrasulfide is uniquely stabilized by solvent coordination so that solutions of Na₂S₄ in these amides are stable for long periods of time at 130°C.     

Protein-Polysaccharide Interactions for Stabilization of Food Emulsions

Proteins, polysaccharides and their blends, as examples of natural biopolymers, are surface active materials. Biopolymers may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific conditions (such as protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing processing), it has been stated that proteins and polysaccharides form hybrids (complexes) with enhanced functional properties in comparison to the proteins and polysaccharides alone. Different protein-polysaccharide pairs are reviewed with particular attention to the emulsification capability of their mixtures. In the case of uncomplexed blends of biopolymers, competitive adsorption onto hydrophobic surfaces is generally reported. Conversely, electrostatic complexation between oppositely charged proteins and polysaccharides allows better anchoring of the new-formed macro-molecular amphiphile onto oil-water interfaces. Moreover, improved thermal stability and increased resistance to external treatment (high pressure) involved in food processing are obtained. This review presents basic and applied knowledge on protein-polysaccharide interactions in aqueous medium and at the oil-water interface in food emulsion systems. Electrostatic interactions and thermodynamic incompatibility in mixed biopolymer solutions are correlated to the functional properties (rheology, surface hydrophobiciry, emulsification power) of these interesting blends. Basic and industrial selected systems of different families of hydrocolloids (as gum Arabic, galactomannans, pectins) and protein (caseins, whey, soya, gelatin) mixtures are reviewed.     

Crystallization of Celecoxib in Microemulsion Media

Celecoxib belongs to a new NSAID family specifically inhibiting cyclooxygenase‐2 (COX‐2). The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. We solubilized celecoxib in micelles of nonionic microemulsions and hydrophilic surfactant. The supersaturated solubilized drug was precipitated from the nano‐droplets to form a new solid structure with improved dissolution properties. The selected microemulsion systems loaded with celecoxib were characterized by SAXS, SD‐NMR, viscosity, and electrical conductivity techniques. Precipitation was conducted from W/O as well as from O/W U‐type microemulsions. The crystals obtained by the precipitation were characterized by x‐ray powder scattering, differential scanning calorimetry, FTIR measurements, and microscopic scans.     

Surface morphological and impedance spectroscopic studies on the interaction of polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) with mild steel in acid solutions

The inhibition of mild steel corrosion in aerated acid mixture of 0.5 N H₂SO₄ and 0.5 N HCl solution was investigated using potentiodynamic polarization studies, linear polarization studies, electrochemical impedance spectroscopy, adsorption, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, degree of surface coverage, adsorption kinetics, and surface morphology is investigated. The inhibition efficiency increased markedly with increase in additive concentration. The presence of PEG and PVP decreases the double-layer capacitance and increases the charge-transfer resistance. The inhibitor molecules first adsorb on the metal surface following a Langmuir adsorption isotherm. Both PEG and PVP offer good inhibition properties for mild steel and act as mixed-type inhibitors. Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that PVP offers better protection than PEG.