A mechanism for the decomposition of dinitropropyl compounds

A decomposition mechanism is proposed for 2,2-dinitro-1-methoxypropane, a compound whose structure resembles the nitroplasticizer (NP) component of plastic-bonded explosive PBX 9501. A library of key reactions is presented and is based on the results of NP aging studies and existing decomposition mechanisms for similar nitro compounds. Density functional electronic structure calculations on these reactions were used to develop a decomposition mechanism at lower temperatures, which begins with HONO elimination and leads to intermediates that can produce CO, CO(2), NO, and N(2)O gases. These gases were observed in low temperature (48 to 64 degrees C) aging studies of NP. A high temperature mechanism involving NO(2) scission is compared to a thermal decomposition mechanism determined by simultaneous thermogravimetric modulated beam mass spectrometry. The calculated energy barriers for HONO elimination and NO(2) scission in the gas phase are reported and compared to experimental results.     

Redox control of meso-zinc(II) ferrocenylporphyrin based fluorescence switches

The efficient on/off switching of fluorescence from thienyl- and phenyl-substituted porphyrin-ferrocene dyads is achieved through redox control of excited-state electron-transfer quenching.     

Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane as ligands for Cu(II), Ni(II), Cd(II), Zn(II), and Fe(III) in aqueous solution

Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane (ATZ-SSQ) were tested as ligands for transition-metal ions in aqueous solution with a special attention to sorption isotherms, ligand-metal interaction, and determination of metal ions in natural waters. The adsorption potential of the material ATZ-SSQ was compared with related [3(3-amino-1,2,4-triazole)propyl]silica gel (ATZ-SG). The adsorption was performed using a batchwise process and both organofunctionalized surfaces showed the ability to adsorb the metal ions from aqueous solution. The Langmuir model was used to simulate the sorption isotherms. The results suggest that the sorption of these metals on ATZ-SSQ and ATZ-SG occurs mainly by surface complexation. The equilibrium condition is reached at time lower than 3 min for ATZ-SSQ, while for ATZ-SG is only reached at time of 25 min. The maximum metal ion uptake values for ATZ-SSQ were higher than the corresponding values achieved with the ATZ-SG. In order to obtain more information on the ligand-metal interaction of the complexes on the surface of the ATZ-SSQ nanomaterial, ESR study with various degrees of copper loadings was carried out. The ATZ-SSQ was tested for the determination (in flow using a column technique) of the metal ions present in natural waters.     

Stereoselective synthesis of a MCHr1 antagonist

Melanin-concentrating hormone (MCH) is implicated in the feeding behavior in mammals affording a potential target to control overeating in people. Compound 1 (AMG 076) has been identified as a potent MCHr1 antagonist for the treatment of obesity. A synthesis suitable for the large-scale preparation of this lead candidate was developed to support preclinical studies. A Robinson annulation of benzylpiperidone and resolution of the desired enone from a mixture of the diastereomers afforded key intermediate 6 after a stereoselective hydrogenation. Subsequent Fischer indole synthesis with hydrazine 5 then provided the advanced intermediate, indole 2. Two complementary reductive amination strategies employing either aldehyde 3 or lactol 4 led to the synthesis of title compound 1.     

Immobilization of hexokinase onto chitosan decorated particles

Chitosan (CH) decorated polystyrene (PS) particles were synthesized within complexes of CH, a polycation under acid conditions, and tiny amounts of sodium dodecylsulfate (SDS). Particle characterization was performed by means of dynamic light scattering, zeta potential measurements, and transmission electron microscopy. All dispersions were stable in the ionic strength of 2.0 mol L-1 NaCl during 2 months. The outstanding colloidal stability was attributed to the presence of a hydrated CH layer around the particles. CH decorated PS particles were attached to atomic force microscopy cantilevers and probed against Si wafers in water and in NaCl 0.01 mol/L. The mean thickness of CH layer amounted to 35 +/- 11 and 16 +/- 6 nm, when the medium was water and NaCl 0.01 mol/L, respectively. Adsorption isotherm of hexokinase (HK) onto PS/CH particles studied by means of spectrophotometry showed three regions: an initial step; adsorption plateau and multilayer formation. Enzymatic activity of free HK and immobilized HK was monitored by means of spectrophotometry as a function of storing time and reuse. After 3 days, storing HK free in solution dramatically lost its catalytic properties. On the contrary, HK-covered PS/CH particles retained enzymatic activity over 1 month. Moreover, HK-covered PS/CH particles could be reused in the determination of glucose two times consecutively, without losing activity. These interesting findings were discussed in light of the role of water in enzyme conformation.     

An Easy Way Toward ε‐Caprolactone Macromonomers by Microwave Irradiation Using Early Lanthanide Halides as Catalysts

Poly(ε‐caprolactone) macromonomers were synthesized under microwave irradiation from commercial caprolactone, using commercial hydrated lanthanide halides as catalysts. The molecular weight of the polymers was in the range 3 000–5 000. Higher molecular weights (5 000–20 000) and lower polydispersity indices were obtained with THF adducts of the lanthanide halides as catalysts and also by applying longer reaction times or using diethylene glycol as a coupling reagent.     

Cellulosic Films Obtained from the Treatment of Sugarcane Bagasse Fibers with N-methylmorpholine-N-oxide (NMMO)

Ethanol/water organosolv pulping was used to obtain sugarcane bagasse pulp that was bleached with sodium chlorite. This bleached pulp was used to obtain cellulosic films that were further evaluated by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). A good film formation was observed when temperature of 74 °C and baths of distilled water were used, which after FTIR, TGA, and SEM analysis indicated no significant difference between the reaction times. The results showed this to be an interesting and promising process, combining the prerequisites for a more efficient utilization of agro-industrial residues.     

Novel zirconocene anticancer drugs?

From the reaction of Super Hydride (LiBEt₃H) with 6-(4-methoxyphenyl) fulvene (1a), 6-(2-fluoro-4-methoxyphenyl) fulvene (1b), and 6-(4-N,N-dimethylaminophenyl) fulvene (1c) lithiated cyclopentadienide intermediates (2a-c) were synthesised. These intermediates were then transmetallated to zirconium with ZrCl₄ to give benzyl-substituted zirconocenes bis-[(4-methoxybenzyl)cyclopentadienyl] zirconium(IV) dichloride (3a), bis-[(2-fluoro-4-methoxybenzyl)cyclopentadienyl] zirconium(IV) dichloride (3b) and bis-[(4-N,N-dimethylaminobenzyl)cyclopentadienyl] zirconium(IV) dichloride (3c). All three zirconocenes were characterised by single crystal X-ray diffraction and preliminary in vitro cell tests were performed with the zirconocene derivatives on the LLC-PK cell line in order to determine their cytotoxicity. Zirconocenes 3b and 3c did not show cytotoxicity up to a concentration of 170 μM, while 3a exhibited an IC50 value of 57 μM against LLC-PK.