Hydrogen oxidation reaction on platinum nanoparticles: Transition between mechanistic routes

The present work reports for the first time results which demonstrate that the hydrogen oxidation reaction on platinum nanoparticles supported on gold and glassy carbon substrates displays a transition between the Tafel–Volmer route, which dominates at low overpotentials, and the Heyrovsky–Volmer route, predominant at high overpotentials.     

Fatty acid derived phosphorus‐containing polyesters via acyclic diene metathesis polymerization

The acyclic diene metathesis (ADMET) polymerization of a phosphorus‐containing α,ω‐diene prepared from a plant oil derived building block is reported. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of this monomer. Undecylenyl undecenoate was used as fully renewable comonomer to obtain polyesters with different phosphorus contents and to increase the renewable content of the final polymers. Copolymerization caused marked variations in the molecular weights leading to polyesters from 6 to 38 KDa. The effect of the ADMET polymerization temperature in the thermal properties of the copolymers was studied and their thermal degradation and flame retardant properties were evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5760–5771, 2009     

Reactions of 2,5-di(2-thienyl)pyrroles

We have studied the possible modification of 2,5-di(thienyl)pyrroles with the aim of preparing compounds which can serve as precursors of polymers and monomers showing electrical conductivity and specific photochemical properties. Dedicated to Boris Aleksandrovich Trofimov on his 70^th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1356–1365, September, 2008.     

Synthesis and applications of a chiral-oxygenated 3-chloro-3,6-dihydro-2H-pyran obtained under Overman rearrangement conditions

A chlorinated side product was formed under Overman rearrangement conditions from a trichloroacetimidate along with the expected allylic amide. The chlorinated product derived from a hex-2-enopyranoside was obtained in a totally stereoselective manner, and it can be a useful synthetic intermediate for chlorinated sugars. In order to improve the isolated yields of either the expected Overman rearrangement product or the chlorinated compound, we carried out a thorough study on the experimental conditions. The application of the latter for the synthesis of potential calpain inhibitors is also reported.     

Atmospheric and soil degradation of aliphatic-aromatic polyester films

The degradation of an aliphatic-aromatic biodegradable polyester film was studied under conditions of solar exposure and soil burial in a tropical area. Film samples were evaluated for changes over 40 weeks by visual examination, scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical properties, molecular weight, gel content, and thermal properties. Photodegradation played a major role in the atmospheric degradation of the film, causing it to lose integrity and mechanical properties after week 8 due to main chain scission and crosslinking. SEM micrographs and FTIR spectra indicated that photodegradation started at the exposed side of the film and propagated through the polymer matrix after week 8. FTIR spectra also indicated that subsequent photooxidation processes took place. The reduction of molecular weight of the soil burial samples was much slower than that of the non-crosslinked portion of solar exposed film samples. The reduction of number average molecular weight of the non-crosslinked solar exposed samples followed a first order reaction, whereas the soil burial samples show a surface erosion biodegradation behavior. The relationship among total solar radiation, gel content and number average molecular weight indicated that an accumulated total solar radiation of 800 MJ/m², reached in approximately 7 weeks at the exposure site, is required for PBAT mulch film integrity loss.     

Electronic structure and reactivity of 3-acetyl-2-methylbenzo[b]thiophene: a quantum chemical study

The electronic structures of 3-acetyl-2-methylbenzothiophene, the cations resulting from its C-protonation at positions 4?C7 and O-protonation, and the dications formed upon protonation at positions 4?C7 of the O-protonation product were studied by the MNDO, HF/3-21G, and B3LYP/3-21G methods. Analysis of the relative energies of these cations and dications is in line with the earlier authors?? data on the predominant reactivity of positions 4 and 6 of the 3-acetyl-2-methylbenzothiophene molecule toward acylation.     

Barlow-wu continuum systems: A discussion on the model

Barlow-Wu continuum structure functions have been introduced in the past as one particularly interesting family of continuum structure functions. In this paper we provide an alternative characterization for such continuum structure functions, showing other interesting properties. Research supported by Dirección General de Investigación Científica y Técnica (DGICYT), national grants number PB91-0389 and number BE91-225.     

Lyapunov inequalities for partial differential equations

This paper is devoted to the study of Lp Lyapunov-type inequalities (1?p?+∞) for linear partial differential equations. More precisely, we treat the case of Neumann boundary conditions on bounded and regular domains in RN. It is proved that the relation between the quantities p and N/2 plays a crucial role. This fact shows a deep difference with respect to the ordinary case. The linear study is combined with Schauder fixed point theorem to provide new conditions about the existence and uniqueness of solutions for resonant nonlinear problems.