Optimization and Validation of Rancimat Operational Parameters to Determine Walnut Oil Oxidative Stability

This study was performed to optimize and validate Rancimat (Metrohm Ltd., Herisau, Switzerland) operational parameters including temperature, air-flow, and sample weight to minimize Induction-Time (IT) and IT-Coefficient-of-Variation (CV), using Response Surface Methodology (RSM). According to a Box–Behnken experimental design, walnut oil equivalent to 3-, 6-, or 9-g was added to each reaction vessel and heated to 100, 110, or 120 °C, while an air-flow equal to 10-, 15-, or 20-L·h−1 was forced through the reaction vessels. A stationary point was found per response variable (IT and CV), and optimal parameters were defined considering the determined stationary points for both response variables at 100 °C, 25 L·h−1, and 3.9 g. Optimal parameters provided an IT of 5.42 ± 0.02 h with a CV of 1.25 ± 0.83%. RSM proved to be a useful methodology to find Rancimat operational parameters that translate to accurate and efficient values of walnut oil IT.

A palladium-catalyzed cascade process for spirooxindole: an alternative way for the synthesis of spiro(indoline-3,2′-quinazolin)-2-ones

A palladium-catalyzed synthetic strategy has been developed for one-pot synthesis of functionalized spiro(indoline-3,2′-quinazolin)-2-one derivatives from 2-aminobenzonitriles, arylboronic acids and isatins. This cascade strategy proceeds via successive C–C and two C–N bond formations in a single reaction vessel.

Doubleisomerization / cycloisomerization / aromatization of 1-(allyloxy)-2-(cyclopropylmethyl)benzenes to give 2-ethyl-3-isopropylbenzofurans using multitasking single rhodium catalyst

Multitasking single-catalyst systems that allow multiple chemical transformations within a single reaction vessel are important for the development of eco-compatible chemistry. Here, we have developed a rhodium-catalyzed system that transforms...

Microwave-Assisted Acid Digestion: Evaluation of Reaction Vessel Design and Performance

Nowadays, microwave-assisted procedures using closed vessels with thermal, chemical, and mechanical resistance are the state-of-the-art for efficient digestion of samples. Safety issues related to sample reactivity should be considered and analytical throughput is also a critical parameter. The choice of a specific vessel for a target application is not trivial and simple experiments are presented here for rice flour and bovine liver samples to illustrate effects of vessel design on digestion performance. Despite using the same heating program, the residual carbon contents varied from 22 to 67% to bovine liver digests and from 7 to 96% to rice flour digests. Quantitative recoveries were obtained for most analytes. Low recoveries were observed mainly for Ca and Fe. Analytical performance is related to different sizes, shapes and the gradient of temperature for each model of digestion vessel. It was demonstrated that taller vessels improved regeneration of nitric acid.

Создание ZnO нанокатализатора, фиксированного на подложке, и перспективы фотокаталитического получения биогаза из растительных отходов

In this work discuss the production of biofuels from agricultural waste, such as sugars, alcohols, organic acids, by obtaining hydrogen and biogas from them during photocatalytic decomposition. Possible chemical reactions during photocatalysis are presented using the example of photocatalytic decomposition of methanol into hydrogen and carbon dioxide. Experiments on the preparation of nanostructured ZnO by the hydrothermal method in a solution containing zinc acetate and urotropin have been carried out. The obtained ZnO immobilized on a substrate is supposed to be used as a photocatalyst. A possible design of a reaction vessel and radiation sources for a laboratory setup for producing biogas from model solutions are considered. Key words: photocatalysis, biogas, ZnO, nanowires, waste disposal, renewable energy.

REAÇÕES EM CASCATA ENZIMÁTICA, QUIMIOENZIMÁTICA E FOTOENZIMÁTICA: PERSPECTIVAS PARA UMA SÍNTESE ORGÂNICA MAIS SUSTENTÁVEL

ENZYMATIC, CHEMOENZYMATIC AND PHOTOENZYMATIC CASCADE REACTIONS: PERSPECTIVES FOR A MORE SUSTAINABLE ORGANIC SYNTHESIS. Chemicals are rarely the result of a single transformation but rather the consequence of several individual reaction steps. Classically, these individual steps are carried out in sequence, including isolation and purification of the intermediate products. However, the reasons for choosing to carry out cascade reactions can be multiple, such as (i) the chance to prepare unstable and/or toxic intermediates, which are consumed directly in a subsequent step, (ii) the option to shift the equilibrium of a reaction by removing the co (product), or (iii) simply bypass the tedious work of isolating and purifying intermediates, saving reagents, solvents, time and money, and still generating less waste. Therefore, it is not surprising that so-called cascade reactions are gaining considerable interest in academic and industrial research. The purpose of this review is to show recent, promising research and new trends, the potential and current limitations of cascade reactions in organic synthesis that involves at least one enzymatic step in the cascade. This review will address cascades involving multi enzymatic, chemoenzymatic, and photoenzymatic cascades, where all steps are performed in one reaction vessel simultaneously or sequentially and the cascades in the regime of continuous flow.

Iron vs. ruthenium: syntheses, structures and IR spectroelectrochemical characterisation of half-sandwich Group 8 acetylide complexes

A synthetic ‘trick’ affording complexes [M(CCR)(dppe)Cp′] (M = Fe, Ru) in high purity directly from the reaction vessel is described.

Ultrasonically-Assisted Dissolution of Sugarcane Bagasse during Dilute Acid Pretreatment: Experiments and Kinetic Modeling

Ultrasonic irradiation is known to enhance various physicochemical processes. In this work, the effect of ultrasound on the dissolution of sugarcane bagasse was studied, with the specific aims of quantifying the effect at low solids loading and mild reaction conditions, and determining whether the enhancement of dissolution by ultrasound is independent of temperature. The effects of agitation speed, reaction time, and sonication were examined on the dissolution of the biomass substrate at varying reaction temperatures during the pretreatment process. Sugarcane bagasse was mixed with a 0.3 M solution of sulfuric acid in a reaction vessel to undergo pretreatment. A kinetic model was applied to the mass dissolution of the biomass, as sonicated runs showed higher mass losses at each reaction time, compared to the non-sonicated runs. The ultrasonic enhancement in mass dissolution was seen to increase for an increase in the reaction time. It was observed that the induction period for the dissolution was eliminated by the application of ultrasound. Ultrasound was found to be more effective than temperature at enhancing mass dissolution at low solids loadings, and the effect of ultrasound was also found to be dependent on the temperature employed.

Dynamic Ion Speciation During Hydrolysis of Aryltrifluoroborates

<p>Organotrifluoroborates serve as a coupling partner during transmetallation in the Suzuki-Miyaura reaction but require hydrolysis prior to the coupling reaction. Their anionic nature allows study of their hydrolysis by electrospray ionization mass spectrometry (ESI-MS) by real-time monitoring, complemented by pH analysis. Induction periods varied according to the borates employed, and a dynamic series of equilibria for numerous ions was observed during hydrolysis. We found that the induction periods and reaction rates were sensitive to the R group of the borates, the shape of reaction vessel, and stir rate, and that after complete decay of all of the aryltrifluoroborate ion the solution contained a variety of partially hydrolyzed species.</p>

Dynamic Ion Speciation During Hydrolysis of Aryltrifluoroborates

<p>Organotrifluoroborates serve as a coupling partner during transmetallation in the Suzuki-Miyaura reaction but require hydrolysis prior to the coupling reaction. Their anionic nature allows study of their hydrolysis by electrospray ionization mass spectrometry (ESI-MS) by real-time monitoring, complemented by pH analysis. Induction periods varied according to the borates employed, and a dynamic series of equilibria for numerous ions was observed during hydrolysis. We found that the induction periods and reaction rates were sensitive to the R group of the borates, the shape of reaction vessel, and stir rate, and that after complete decay of all of the aryltrifluoroborate ion the solution contained a variety of partially hydrolyzed species.</p>