Graft copolymerization onto rubber. V. Graft copolymerization of methyl methacrylate onto rubber using potassium peroxydiphosphate as initiator

The graft copolymerization of methyl methacrylate onto natural rubber (NR) is investigated using potassium peroxydiphosphate as the initiator. The rate of grafting is determined by varying monomer concentration, peroxydiphosphate concentration, and temperature. The graft yield increased with an increase in monomer concentration up to 1.4082M/L and thereafter the graft yield decreases. The graft yield increases significantly with an increase of peroxydiphosphate concentration up to 150 X 10^-1M/L and thereafter the graft yield decreases. The grafting reaction is temperature dependent. A suitable kinetic scheme is proposed and the rate equation is evaluated.     

Ru(bpy) 3 2+ sensitized photopolymerization ofN,N′-methylene-bisacrylamide

Photochemical polymerization ofN,N′-methylenebisacrylamide (MBA) initiated by the dye-reducing agent rhodamine-B-allylthiourea (ATU) system is enhanced by the addition of small amounts oftris(2,2′-bipyridine)-ruthenium(II), Ru(bpy) ₃ ²⁺ , a result attributed to the efficient formation of chain-initiating allylthiourea radicals in the presence of Ru(bpy) ₃ ²⁺ ions. The rate of polymerization was found to be proportional to [Ru(bpy) ₃ ²⁺ ]^0.5, [rhodamine-B]^0.5, [ATU]^0.5 and [MBA]^1.0. A probable mechanism consistent with the observed results is proposed and discussed. TMC 2391     

Synthesis,biological evaluation and molecular docking studies of novel 2-(2-cyanophenyl)-N-phenylacetamide derivatives

A series of novel 2-(2-cyanophenyl)-N-phenylacetamide derivatives 3(a-u) were designed and synthesized via selective amidation of methyl-2-(2-cyanophenyl)acetates over amidine formation by using AlMe₃ as catalyst in good yields. All the newly synthesized derivatives were well characterized by ¹H NMR, ¹³C NMR, FTIR and HRMS spectral techniques. All the synthesized title compounds were evaluated for their in vitro anticancer activity against three cancer cell lines. Among all compounds, 3i (IC₅₀?=?1.20 μM, IC₅₀?=?1.10 μM), 3j (IC₅₀?=?0.11 μM, IC₅₀?=?0.18 μM), 3o (IC₅₀?=?0.98 μM, IC₅₀?=?2.76 μM) showed excellent inhibitory activity than the standard Etoposide (IC₅₀?=?2.11 μM, IC₅₀?=?3.08 μM) against MCF-7 and A-549 cell lines, respectively. Docking analysis of all the compounds with the human topoisomerase II revealed that the compound 3j fitted well in the active site pocket, showing the best docking score of 158.072 kcal/mol.

     

The methanol-induced conformational transitions of β-lactoglobulin, cytochrome c, and ubiquitin at low pH: A study by electrospray ionization mass spectrometry

The methanol-induced conformational transitions under acidic conditions for beta-lactoglobulin, cytochrome c, and ubiquitin, representing three different classes of proteins with beta-sheets, alpha-helices, and both alpha-helices and beta-sheets, respectively, are studied under equilibrium conditions by electrospray ionization mass spectrometry (ESI-MS). The folding states of proteins in solution are monitored by the charge state distributions that they produce during ESI and by hydrogen/deuterium (H/D) exchange followed by ESI-MS. The changes in charge state distributions are correlated with earlier studies by optical and other methods which have shown that, in methanol, these proteins form partially unfolded intermediates with induced alpha-helix structure. Intermediate states formed at about 35% methanol concentration are found to give bimodal charge state distributions. The same rate of H/D exchange is shown by the two contributions to the bimodal distributions. This suggests the intermediates are highly flexible and may consist of a mixture of two or more rapidly interconverting conformers. H/D exchange of proteins followed by ESI-MS shows that helical denatured states, populated at around 50% methanol concentration, transform into more protected structures with further increases in methanol concentration, consistent with previous circular dicroism studies. These more protected structures still produce high charge states in ESI, similar to those of the fully denatured proteins.     

Synthesis of sulfur‐containing heterocycles: spiropyrimidinetriones,thioxopyrimidinediones, pyrazolidinediones,and isoxazolidinediones—part ii

1‐Aroyl‐2‐styrylsulfonylethene is the precursor for 4,4‐dimethoxycarbonyl‐2′,5‐diaryl‐3‐(1′,3′‐dioxolano)‐1‐thia‐1,1‐dioxide ( 4 ), which is the key intermediate for the synthesis of 7‐aroyl‐11‐aryl‐2,4‐diazaspiro[5,5]undecane‐1,3,5‐trione‐9‐thia‐9,9‐dioxide( 10 )/3‐thioxo‐1,5‐dione‐9‐thia‐9,9‐dioxide ( 11 ), 6‐aroyl‐10‐aryl‐2,3‐diazaspiro[4,5]decane‐1,4‐dione‐8‐thia‐8,8‐dioxide ( 12 )/2‐oxo‐3‐azaspiro [4,5]decane‐1,4‐dione‐8‐thia‐8,8‐dioxide ( 13 ). The new compounds were characterized by IR and ¹H NMR spectral data. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:131–135, 2001     

Pd-Catalyzed Regioselective Domino C−C Bond Formation to Access N-Fused Benzimidazo-Indolo-Isoquinoline Heterocycles

Regioselective synthesis of N-fused benzimidazo-indolo-isoquinoline heterocycles via Pd-catalyzed domino coupling reaction of 1-(1-methyl-1H-indol-2-yl)-1H-benzimidazoles and aryl halides was developed. This one pot methodology proceeded via a five-member carbopalladacycle intermediate and provided direct and facile route to access structurally complex polyheterocycles in moderate to good yields. These unique hybrid molecules resembled structural similarity with naturally isolated alkaloids. Notably, the present domino process occurred through activation of three C−H bonds and the simultaneous formation of two new C−C bonds in one-shot. These molecules exhibited strong solid and solution phase fluorescence and their emission spectra in both the medium are reported here.     

Intermolecular Carbophosphination of Alkynes with Phosphole Oxides via Ni−Al Bimetal-Catalyzed C−P Bond Activation

Intermolecular carbophosphination reaction of alkynes or alkenes with unreactive C−P bonds remains an elusive challenge. Herein, we used a Ni−Al bimetallic catalyst to realize an intermolecular carbophosphination reaction of alkynes with 5-membered phosphole oxides, providing a series of 7-membered phosphepines in up to 94 % yield.     

Amperometric hydrogen peroxide sensor based on the use of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> hollow nanostructures

The authors report on the preparation of a hollow-structured cobalt ferrite (CoFe₂O₄) nanocomposite for use in a non-enzymatic sensor for hydrogen peroxide (H₂O₂). Silica (SiO₂) nanoparticles were exploited as template for the deposition of Fe₃O₄/CoFe₂O₄ nanosheets, which was followed by the removal of SiO₂ template under mild conditions. This leads to the formation of hollow-structured Fe₃O₄/CoFe₂O₄ interconnected nanosheets with cubic spinel structure of high crystallinity. The material was placed on a glassy carbon electrode where it acts as a viable sensor for non-enzymatic determination of H₂O₂. Operated at a potential of ?0.45 V vs. Ag/AgCl in 0.1 M NaOH solution, the modified GCE has a sensitivity of 17 nA μM^?1 cm^?2, a linear response in the range of 10 to 1200 μM H₂O₂ concentration range, and a 2.5 μM detection limit. The sensor is reproducible and stable and was applied to the analysis of spiked urine samples, where it provided excellent recoveries.

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Graphical abstract Schematic of a cobalt ferrite (CoFe₂O₄) hollow structure for use in electrochemical determination of H₂O₂. The sensor shows a low detection limit, a wide linear range, and excellent selectivity for H₂O₂.

     

Analysis of thermal,oxidative and cold flow properties of methyl and ethyl esters prepared from soybean and mustard oils

Oilseed crop with high oil content and promising ecological adaptability are potential sources for competitive biodiesel production. This study investigates the scope of utilizing biodiesel development through the methyl and ethyl ester from soybean and mustard oil as an alternative fuel. Methyl and ethyl esters of oils having different fatty acids compositions such as soybean (SOME and SOEE) and mustard oil (MUME and MUEE) were prepared by transesterification with methanol and ethanol in the presence of an alkali-KOH catalyst. The gas chromatographic (GC) analysis of oil samples revealed that primary fatty acid composition in soybean oil was linoleic acid (C_18:2, 51.93%), followed by oleic acid (C_18:1, 22.82%), palmitic acid (C_16:0, 11.56%), linolenic acid (C_18:3, 5.95%) and stearic acid (C_18:0, 4.32%). Whereas, the main components in mustard oil were erucic acid (C_22:1, 32.81%), oleic acid (C_18:1, 24.98%), eicosenoic acid (C_20:1, 10.44%), linolenic acid (C_18:3, 8.61%) and palmitic acid (C_16:0, 2.80%). The physicochemical properties (acid value, iodine value, calorific value, flash point, pour point etc.) of methyl and ethyl ester samples were estimated and found to be within the acceptable range of ASTM D6751 standards specifications. The prepared esters and oil samples were examined for cold flow properties by differential scanning calorimetry (DSC). Results revealed better cold flow properties for MUME (−2.55 °C) and MUEE (−3.10 °C) than SOME (3.21 °C) and SOEE (1.83 °C) due to more unsaturated fatty acid content in MU. Thermal and oxidative stability of samples was determined by thermogravimetric analysis (TG) and differential thermal analysis (DTA). The thermal and oxidative stability ranking of the samples was in the order of oil > methyl esters > ethyl esters.