Cu-Catalyzed alkylation–cyanation type difunctionalization of styrenes with aliphatic aldehydes and TMSCN via decarbonylation

A copper-catalyzed decarbonylative alkylation–cyanation of styrene derivatives with aliphatic aldehydes and trimethylsilyl cyanide to provide chain elongated nitriles is reported. Using TBHP as oxidant and free radical initiator, the reaction...

MASTIC-G-POLY (ACRYLAMIDE): MICROWAVE-ASSISTED SYNTHESIS AND CHARACTERISATION

Objective: The objective of the present investigation was the synthesis of grafted co-polymer gum mastic using acrylamide as the monomer. Methods: 3-factor 3-level response surface Box-Behnken design, which requires 15 runs including three replicates of the central run, was used for the synthesis of graft copolymers of mastic gum with acrylamide using ceric ammonium nitrate as the free radical initiator. The critical synthesis and process parameters; CSPP (A = concentration of monomer, B = concentration of initiator and C= Temperature) to generate design space and optimize formulation with an aim to obtain critical quality attributes (CQA, Y1 =% Yield, Y2 =% Grafting, Y3 =% grafting efficiency). Result: Formulation F14 having a maximum % yield of 75.89% with % grafting of 210% and % grafting efficiency 51.57% was selected as best. Conclusion: The microwave-assisted grafted mastic gum was prepared successfully and optimized by using Box Behnken design.

A Theoretical Antioxidant Mechanism for Cytoprotective Effect of p-AcetamideSalicylate Derivatives against Free Radical Initiator AAPH in Human Erythrocytes

The molecular mechanism of cytoprotective effect on human erythrocytes of aminophenol and salicylates associated derivatives was related to their antioxidant capacity. The oxidative hemolysis induced by water-soluble free-radical initiator 2,2’-azobis-(2-amidine-propane)-dihydrochloride (AAPH) was inhibited by drug candidates named benzaminophen (BZL), salicytamide or 5-acetamide-salicylic acid (ASL), and salibenzamide or 5-benzamide-salicylic acid (BSL) when compared to their parents salicylic acid (SAC) and acetaminophen (ACP). Trolox (TLX) was the most powerful compound and used as positive control. BZL showed a potent effect followed by ACP > BSL > ASL. SAC did not show protective effect in any evaluated concentrations. These results are in accordance with the molecular mechanism by using theoretical calculation of single electron transfers (SET), hydrogen atom transfers (HAT), and sequential proton loss electron transfer (SPLET) by means of DFT/B3LYP/6-31++G(d,p) level of theory. [1,5] Hydrogen shift between carboxyl and phenol moieties and electronic properties related to pKa and other physicalchemical properties can be involved. The molecular association approach provides protective compounds more effective than SAC.

pH-Dependent Foam Formation Using Amphoteric Colloidal Polymer Particles

Near-monodispersed micrometer-sized polystyrene (PS) particles carrying amidino and carboxyl groups on their surfaces were synthesized by soap-free emulsion polymerization using an amphoteric free radical initiator. The resulting amphoteric PS particles were characterized in terms of diameter, morphology, disperibility in aqueous media and surface charge using scanning electron microscopy (SEM), optical microscopy (OM), sedimentation rate and electrophoretic measurements. At pH 2.0, where the amidino groups are protonated (positively charged), and at pH 11.0, where the carboxyl groups are deprotonated (negatively charged), the PS particles were well dispersed in aqueous media via electrostatic repulsion. At pH 4.8, where the surface charges are neutral, the PS particles were weakly aggregated. Furthermore, it was confirmed that the PS particles can function as a pH-sensitive foam stabilizer: foamability and foam stability were higher at pH 2.0 and 4.8, where the PS particles can be adsorbed to the air–water interface, and lower at pH 11.0, where the PS particles tend to disperse in bulk aqueous medium. SEM and OM studies indicated that hexagonally close-packed arrays of PS particles were formed on the bubble surfaces and moiré patterns were observed on the dried foams. Moreover, the fragments of dried foams showed iridescent character under white light.

PHYSICO-MECHANICAL AND DYNAMIC MECHANICAL PROPERTIES OF META-PENTADECENYL PHENOL FUNCTIONALIZED ACRYLONITRILE–BUTADIENE RUBBER NANOCLAY COMPOSITES

ABSTRACT The physico-mechanical and thermo-mechanical properties of meta-pentadecenyl phenol (cardanol) functionalized acrylonitrile–butadiene rubber (CGNBR) composites containing sodium montmorillonite clay were determined via studies on the functionalization of NBR by grafting cardanol onto its backbone main chain in the latex stage using benzoyl peroxide as a free radical initiator. Results show an improvement in technical properties for functionalized NBR nanocomposites over the NBR nanocomposite. Air and ASTM 3 oil aging studies at 100 °C confirmed an increase in tensile strength and a decrease in elongation at break for CGNBR compared to the dioctyl phthalate plasticized NBR nanocomposite. Fire and flame retardancy studies showed an increased limiting oxygen index for functionalized NBR over the NBR nanoclay composite. Results delineate the method of preparation and characterization of functionalized NBR and oil plasticized NBR nanoclay composites to achieve an improved oil resistance effect for functionalized NBR over NBR nanocomposite.

Effect of Oxygen and Initiator Solubility on Admicellar Polymerization of Styrene on Silica Surfaces

Although admicellar polymerization has been termed the surface analog of emulsion polymerization, previous reports utilizing free radical-initiated admicellar polymerization relied on high levels of the free radical initiator when compared to emulsion polymerization, likely due to the presence of oxygen in the reported admicellar polymerization systems. Admicellar polymerizations of styrene on the surface of precipitated silica initiated by either a water-soluble or a water-insoluble initiator were studied to determine the effect of dissolved oxygen and free radical initiator solubility on the kinetics, yield, and molecular weight of the polymer formed. Results show that the presence of oxygen reduces the polymer yield and limits molecular weight. The solubility of the initiator also affected the polymer formed in the admicellar polymerization of styrene. While monomer conversions and polymer yield were similar, the molecular weights of polymerizations initiated by a water-soluble initiator were higher than comparable polymerizations initiated by a water-insoluble initiator.