Synthesis of styrene–acrylamide copolymer by surfactant‐free sonicated dynamic interfacial polymerization

This paper summarizes a study on emulsifier‐free ultrasonically assisted in situ dynamic interfacial emulsion copolymerization process of acrylamide and styrene. The resulting emulsions are stable and uniform for several months. Thermogravimetric analysis (TGA) curves and reaction conversion measurements have provided an important knowledge regarding the emulsifier‐free polymerization method. Solvent extractions (water, methanol, and xylene) have shown that the polymerization product is essentially a styrene–acrylamide copolymer. The copolymer produced is a block copolymer, PS‐b‐PAM, where each block contains small amounts of the other comonomer. The produced emulsions are film forming at room temperature in spite of the very high block T_gs, owing to a unique water plasticization effect of the polyacrylamide blocks. Some films prepared from the PS‐b‐PAM have resulted in clear and transparent films. The presented interfacial dynamic polymerization process is fast, reaching 81% conversion within 2 hr of sonication at 4°C (low temperature owing to molecular weight and kinetic considerations), and produces very stable PS‐b‐PAM emulsions. TGA was extensively used as an analytical tool for determination of the reaction parameters and composition of the acrylamide–styrene copolymers. Copyright © 2011 John Wiley & Sons, Ltd.     

Interplay between an elusive 4-(isopropylamino)imidazol-2-ylidene and its isolable mesoionic tautomer, and associated reactivities

An elusive free 4-(isopropylamino)imidazol-2-ylidene is engaged in a tautomeric equilibrium with its mesoionic tautomer, 4-(isopropylamido)imidazolium, which displays the typical reactivity of a cyclic diaminocarbene; once coordinated to a Rh(I) centre, it undergoes a smooth 4e(-) oxidation of its backbone to yield an amido-amidino-carbene, a weak electron donor viable only in its complexed form.     

Mutation scanning-based analysis of Theileria orientalis populations in cattle following an outbreak

Bovine theileriosis is a tick-borne disease caused by one or more hemoprotozoan parasites of the genus Theileria. In the past, Theileria infection in cattle in Australia was largely asymptomatic and recognized to be associated with Theileria buffeli. However, outbreaks of theileriosis have occurred in beef and dairy cattle in subtropical climatic regions (New South Wales) of Australia. There is also one published report of a recent theileriosis outbreak in a beef farm near Seymour in the southeastern state of Victoria. In order to gain an improved insight into the genetic composition of Theileria populations following this outbreak, we undertook herein an integrated PCR-coupled mutation scanning-sequencing-phylogenetic analysis of sequence variation in part of the major piroplasm surface protein (MPSP) gene within and among samples from cattle involved in the outbreak. Theileria DNA was detected in 89.4% of 94 cattle in the Seymour farm; the genetic analysis showed that the ikeda and chitose genotypes representing the Theileria orientalis complex were detected in 75 and 4.8% of 84 infected cattle, respectively, and that mixed populations of these two genotypes were found in 20.2% of infected cattle. Given unpublished reports of a significant increase in the number of outbreaks in Victoria, future investigations should focus sharply on elucidating the epidemiology of Theileria to subvert the economic impact on the cattle industry in this state. Although used here to explore genetic variation within the T. orientalis complex in Australia, a mutation scanning-based approach has broad applicability to other species of Theileria in other countries.     

Synthesis of certain 2-substituted-1H-benzimidazole derivatives as antimicrobial and cytotoxic agents

A series of 2-substituted-1H-benzimidazole derivatives were synthesized and evaluated for antimicrobial, antifungal and cytotoxic activities. The results showed that all tested compounds showed potent antimicrobial activity against some species of Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi) and fungi (Candida albicans) with minimum inhibitory concentrations (MICs) lower than 0.016 μg/mL. In contrast, all tested compounds were inactive against Staphylococcus aureus (Gram-positive bacterium). The final targets were also tested for their antitumor activity in vitro on cervical carcinoma (HeLa) cell line. Eight of the test compounds displayed more potent cytotoxic effect than doxorubicin at nanomolar concentrations. Compounds 2c and 3c exerted the strongest cytoyoxic effect with IC(50) 15 and 13 nM, respectively.     

Hydrothermal Synthesis and Structure of the Solid Solution (Fe<Subscript>0.54</Subscript>Mn<Subscript>0.46</Subscript>)(PO<Subscript>4</Subscript>)⋅2H<Subscript>2</Subscript>O

Abstract  

The iron-manganese phosphate of composition (Fe_0.54Mn_0.46)(PO₄).2H₂O has been obtained as a single-phase product using hydrothermal methods and the structure has been determined by single crystal X-ray diffraction. The title compound is orthorhombic, Pbca, a = 8.720(1), b = 9.884(1), c = 10.114(2) ?, isostructural with strengite. The structure consists of a linkage of MO₆ octahedra and PO₄ ³⁻ tetrahedra. The octahedra are insular and are held together to form a three-dimensional structure by the tetrahedra. The crystal structure study revealed that (Fe_0.54Mn_0.46)(PO₄)⋅2H₂O exhibits a strong Jahn–Teller effect. The compound has been characterized by Raman and IR Spectroscopy, showing the bonds characteristic of the PO₄ ³⁻ polyanions. Measurements by the electric permittivity revealed a peak at 350 K.     

An RP-HPLC determination of 5-hydroxymethylfurfural in honey The case of strawberry tree honey

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0 mg kg⁻¹, respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140 mg kg⁻¹.     

Modification of indium tin oxide films by alkanethiol and fatty acid self-assembled monolayers: a comparative study

Indium tin oxide (ITO) substrates have been modified by alkanethiol and fatty acid self-assembled monolayers (SAMs). The SAMs were grown by dipping the cleaned surface into either a pure alkanethiol or a fatty acid dissolved in various solvents. They were characterized through contact angle, X-ray photoelectron (XPS) and infrared absorption-reflection spectroscopy (IRRAS). Their density and structural organization was found to greatly depend on the cleaning treatment of the ITO surface, the length of the alkyl chain, and, in the case of fatty acids, the concentration of the solution. XPS measurements brought evidence for the fact that, in the case of alkanethiols, the grafting mechanism was through the formation of ionic or covalent bonds involving thiolates. The most prominent result of this comparative study is that thiol-based SAMs are more strongly attached to the ITO substrate and better organized than fatty acids, which we attribute to the fact that the reaction of the ITO surface with fatty acids is more reversible than that with thiols.     

Formation of the 2,4-pentadiynyl-1 radical (H2CCCCCH, X2B1) in the crossed beams reaction of dicarbon molecules with methylacetylene

The chemical dynamics to synthesize the 2,4-pentadiynyl-1 radical, HCCCCCH(2)(X(2)B(1)), via the neutral-neutral reaction of dicarbon with methylacetylene, was examined in a crossed molecular beams experiment at a collision energy of 37.6 kJ mol(-1). The laboratory angular distribution and time-of-flight spectra of the 2,4-pentadiynyl-1 radical and its fragmentation patterns were recorded at m/z = 63-60 and m/z = 51-48. Our findings suggest that the reaction dynamics are indirect and dictated by an initial attack of the dicarbon molecule to the pi electron density of the methylacetylene molecule to form cyclic collision complexes. The latter ultimately rearranged via ring opening to methyldiacetylene, CH(3)-C triple bond C-C triple bond C-H. This structure decomposed via atomic hydrogen emission to the 2,4-pentadiynyl-1 radical; here, the hydrogen atom was found to be emitted almost parallel to the total angular momentum as suggested by the experimentally observed sideways scattering. The overall reaction was strongly exoergic by 182 +/- 10 kJ mol(-1). The identification of the resonance-stabilized free 2,4-pentadiynyl-1 radical represents a solid background for the title reaction to be included into more refined reaction networks modeling the chemistry of circumstellar envelopes and also of sooting combustion flames.     

Synthesis and spectroscopic characterization of copper(II) complexes with the polydentate chelating ligand 4,4'-[1,4-phenylenedi(nitrilo)dipente-2-one

A new series of complexes of 4,4'-[1,4-phenylenenedi(nitilo)]dipenten-2-one, (H(2)L) with CuX(2) x nH(2)O, X = Cl, Br, ClO(4), NO(3) and OAc; n = 1-6 as well as their ethylenediamine adducts have been synthesized and characterized by different physical techniques. The formulation of the complexes is assumed based on their elemental analysis and the molar conductivity. The products are found to be pH-dependent. The IR data showed that the ligand acts as dibasic tetradentate coordinated to copper(II) ions through the enolato-oxygen and the azomethine nitrogen atoms. Electronic, ESR spectra and room temperature magnetic moments indicate that complexes 1-9 are square planar while complexes 10 and 11 are square based pyramidal. The different electronic spectral and ESR parameters are calculated and used to describe the nature of ligand-metal bonding (sigma and pi) as well as to estimate the extent of distortion. A macrocyclic containing copper(II) complex, 12 have been isolated by the reaction of Schiff-base with copper(II)-ethylenediamine mixture. The ligand (H(2)L) is designed as a building block for larger molecules and superamolecular assemblies.