Development Of Chemical Reactions Research Articles

Machine-Learning-Guided Discovery of Electrochemical Reactions.

The molecular structures synthesizable by organic chemists dictate the molecular functions they can create. The invention and development of chemical reactions are thus critical for chemists to access new and desirable functional molecules in all disciplines of organic chemistry. This work seeks to expedite the exploration of emerging areas of organic chemistry by devising a machine-learning-guided workflow for reaction discovery. Specifically, this study uses machine learning to predict competent electrochemical reactions. To this end, we first develop a molecular representation that enables the production of general models with limited training data. Next, we employ automated experimentation to test a large number of electrochemical reactions. These reactions are categorized as competent or incompetent mixtures, and a classification model was trained to predict reaction competency. This model is used to screen 38,865 potential reactions in silico, and the predictions are used to identify a number of reactions of synthetic or mechanistic interest, 80% of which are found to be competent. Additionally, we provide the predictions for the 38,865-member set in the hope of accelerating the development of this field. We envision that adopting a workflow such as this could enable the rapid development of many fields of chemistry.

Drying characteristics and kinetics solar drying of Mediterranean mussel (mytilus galloprovincilis) type under forced convection

Drying is a process of hydration and Elimination of water which allows the proliferation of microorganisms and development of chemical reactions without influencing morphological structure of Food Material. This paper focused on the influence of temperature on drying kinetics of the Mediterranean mussels (mytilus galloprovincilis) as per the requirement for storage seafood. Convective drying kinetics and hygroscopic behavior of Mytilus Galloprovincilis was carried out in a solar dryer operating in forced convection. Experimental drying kinetics were measured at three air temperatures (50, 60, and 70 °C), and two air flow rates fixed at (300 and 150 m3 h−1) with ambient air temperature in the range of 36–42 ± 1 °C, 8.92 to 18.86 ± 2% for ambient humidity, 422 to 988 w/m2 for solar irradiation. Experimental data of drying are collected to plot the characteristic drying curve. Nine mathematical models available in the literature are used for describing the drying curves. The logarithmic model showed the best fitting of experimental data with a highest value of correlation coefficient (r), and lowest value of reduced chi-square (χ2). Effective diffusion coefficient value Deff was obtained between 1.14 10−9 to 3.61 10−9m2s−1 based on the Fick equation.

The influence of velocity field on simple chemical reactions in viscous flow

The paper looks at the nonlinear dynamics of viscous flow in a compressible spatially homogeneous fluid with chemical reactions. Time-dependent exact solution of the Piseuille type is obtained. Proceeding from this solution, the influence of a viscosity effect and a chemical reaction on the characteristics of nonequilibrium temporal states of the system is considered. Special attention is drawn to the effect of density collapses on the development of chemical reactions.

Drying characteristics and kinetics solar drying of Moroccan rosemary leaves

Water contained in foods allows the proliferation of microorganisms and the development of chemical reactions that deteriorate the product. This experimental study is focused on the influence of drying parameters on water loss of fresh rosemary leaves. It presents the experimental study results of the drying kinetics. The drying kinetics of rosemary was carried out in an indirect active solar dryer with a separate solar collector and a drying unit.The drying kinetics was studied for four different air temperatures (50, 60, 70 and 80° C) and two air flows drying (300 m3/h and 150 m3/h) for an ambient temperature in the range of 26–37 °C. The increase of temperature reduced drying duration. The drying time variation according to the drying air flow rate is important for lows temperatures, but not significant for highs temperatures.The experimental results are used to determine the characteristic curve drying. Out of nine models tried for simulation, Midilli kucuk model was found as best fitted thin layer drying model when simulation was done for all the drying data. In the ranges covered, the effective moisture diffusivity values (Deff) were obtained between 9.74 10−11 m2/s and 1.48 10−10 from the Fick’s diffusion model. The Arrhenius relation, with an activation energy value of 54.37 kJ/mol, expressed the temperature effect on the diffusion coefficient.

Effects of Variation in Compaction Water Content on Geotechnical Properties of Lime-treated Clayey Soil

The note presents the results of an experimental research study on the behaviour of a clayey soil of high plasticity treated with 3% quicklime for the stabilization of the foundation soil of a plant to be constructed along a slope. The aim of the study is to investigate the effect of a wide range of water content and of curing time on the mechanical and hydraulic characteristics of the treated soil. Soil-lime samples were prepared by wet mixing and Standard Proctor compaction. The development of chemical reactions in the compacted soil-lime mixtures were monitored by measuring the pH values of the soaking water with curing time. In the long term, a reduction of three orders of magnitude in permeability values was observed by comparing optimum and 5% wet of optimum conditions. Also compressibility was affected by variations in the compaction water content. The shear strength was not significantly affected by water content varying in the considered range.

Asymmetric intramolecular α-cyclopropanation of aldehydes using a donor/acceptor carbene mimetic

Enantioselective α-alkylation of carbonyl is considered as one of the most important processes for asymmetric synthesis. Common alkylation agents, that is, alkyl halides, are notorious substrates for both Lewis acids and organocatalysts. Recently, olefins emerged as a benign alkylating species via photo/radical mechanisms. However, examples of enantioselective alkylation of aldehydes/ketones are scarce and direct asymmetric dialkylation remains elusive. Here we report an intramolecular α-cyclopropanation reaction of olefinic aldehydes to form chiral cyclopropane aldehydes. We demonstrate that an α-iodo aldehyde can function as a donor/acceptor carbene equivalent, which engages in a formal [2+1] annulation with a tethered double bond. Privileged bicyclo[3.1.0]hexane-type scaffolds are prepared in good optical purity using a chiral amine. The synthetic utility of the products is demonstrated by versatile transformations of the bridgehead formyl functionality. We expect the concept of using α-iodo iminium as a donor/acceptor carbene surrogate will find wide applications in chemical reaction development.

Nopal (Opuntia Lasiacantha) Drying Using an Indirect Solar Dryer

Water contained in foods allows the proliferation of microorganisms and the development of chemical reactions that deteriorate. When required preserve food for a time, a dry or dehydrate alternative is removing the water contained therein. There are several ways to achieve this issue, the simplest is to exposed the food into a stream of air with certain conditions of temperature, humidity and velocity. There are several types of solar dryers to achieve proper product treatment. The two basic elements of a solar dryer are manifold where solar radiation heats the air and the drying chamber where the product is dried by the air passing through it, these elements can be designed to integrate the team in different forms. In an indirect solar dryer the two elements are separated, the air is heated in the manifold so that no solar radiation incident on the product placed inside the opaque drying chamber, in this type of dryers the process control drying is simpler. Having a separate drying chamber manifolds facilitates handling of the product and the work of loading and unloading. Since the drying chamber is opaque, this system conveniently dry products that can be damaged by direct sunlight. This project works with an indirect solar dryer having a solar air heater built into its structure with plywood wood 1” thick, both the base and sides, with dimensions of 140cm long and 60cm width, a cover glass thickness of 3mm and an inclination of 17.5° to the horizontal. The main element is a coil of copper foil matt black painted placed inside the structure, isolated base and on all four sides with fiberglass wool, has thirteen channels 10cm x 10cm x 10cm, which means a final length of 5 m in the warm air path, giving a conservative 0.01 m3/s flow and a 1 m/s natural convection speed. The drying chamber is constructed of plywood wood ½” thickness and dimensions of 60cm long, 40cm wide and 55cm high with four nylon mesh trays, allowing initial drying mass about 2kg. The connection between the solar air heater and the drying chamber is performed by means of a neoprene hose with a very low thermal conductivity in its wall. Thermal efficiency is calculated by evaluating the productivity of the dryer measuring temperature, air flow, solar radiation and loss of product mass. Drying curves are obtained graphing Dry Basis Moisture vs. time (X vs. t) and Drying Rate vs. Dry Basis Moisture (ΔX/Δt vs. X) for Nopal (Opuntia Lasiacanta). It is considered that this type of dryer offers several advantages over the common cabinet druer, including the drying rate and product protection from direct sunlight.

A detailed verification procedure for compressible reactive multicomponent Navier–Stokes solvers

The present manuscript reports a numerical verification study based on a series of tests that allows to evaluate the numerical performance of a compressible reactive multicomponent Navier–Stokes solver. The verification procedure is applied to a density-based finite difference numerical scheme suited to compressible reactive flows representative of either combustion in high speed flows or detonation. The numerical algorithm is based on a third-order accurate Total Variation Diminishing (TVD) Runge Kutta time integration scheme. It employs a seventh-order accurate Weighted Essentially Non-Oscillatory (WENO) scheme to discretize the non-linear advective terms while an eighth-order accurate centered finite difference scheme is retained for the molecular viscous and diffusive terms. These molecular contributions are evaluated with the library EGLIB that accounts for detailed multicomponent transport including Soret and Dufour effects. The developed numerical solver thus offers an interesting combination of existing methods suited to the present purpose of studying combustion in high speed flows and/or detonations. The numerical solver is verified by considering a complete procedure that gathers eight elementary verification subsets including, among others, the classical Sod’s shock tube problem, the ignition sequence of a multi-species mixture in a shock tube, the unsteady diffusion of a smoothed concentration profile and a one-dimensional laminar premixed flame. Such verification analyses are seldom reported in the literature but constitute an important part of computational research activities. It is presently completed with the application of the verified finite difference scheme to the numerical simulation of (i) shock (reactive) mixing layer interaction and (ii) combustion ignition downstream of a highly under-expanded jet. The corresponding results shed some light onto the robustness (stability) and performance of the numerical scheme, and also provide some very valuable insights onto the complex physics that prevails in the development of chemical reactions in such situations, which are considered as representative of the discharge or accidental release of high pressure flammable mixtures into the atmosphere.

Solid-state chemical reactions initiated by optical and microwave radiation

It is experimentally demonstrated that the simultaneous exposure of dielectric powders and mixtures to optical and microwave radiation pulses can lead to the development of chemical reactions. This phenomenon is explained by the light-induced absorption of microwave radiation in the dielectric powder, which leads to heating of the mixture and the initiation of a chemical reaction that can subsequently proceed at the expense of the intrinsic heat evolution.

Layer-by-Layer Self-Assembled Polyelectrolyte Multilayers with Embedded Liposomes: Immobilized Submicronic Reactors for Mineralization

The development of chemical reactions in nanospaces is of paramount importance for the development of active nanodevices, particularly in nanofluidics. It has been shown in a previous paper that phospholipid vesicles can be incorporated without spontaneous bilayer rupture into poly-L-glutamic acid/poly(allylamine) (PGA/PAH) multilayered polyelectrolyte films. The aim of the present study was to use such a system as an "embedded submicronic reactor" able to trigger precipitation of calcium phosphates within closed spaces through an enzymatic reaction, the enzyme also being encapsulated in the vesicle interior. To this aim, large unilamellar vesicles (LUVs) were produced containing calcium ions as active ions in the mineralization process, spermine as an activator of crystal growth, and alkaline phosphatase as a catalyst to convert phosphate esters into phosphates. After stabilization by adding a layer of poly-(D-lysine), these vesicles were embedded in a (PGA-PAH)n film. A paranitrophenyl phosphate containing solution was then put in contact with this film. It is shown by means of infrared spectroscopy in the attenuated total reflection mode that, consecutively to this contact, calcium phosphates are growing inside the embedded vesicles. By using scanning near-field fluorescence microscopy, it is demonstrated that the alkaline phosphatase enzymes are most probably located inside the vesicles after their embedding. In addition, atomic force microscopy was used to show, after chemical removal of the organic top layer of the film, that the inorganic platelets produced after the precipitation reaction are localized in volumes of similar size and shape as that of the vesicles into which the phosphate ester hydrolysis and subsequent precipitation reaction did occur.

Monitoring chemical vapour deposition of pyrocarbon by electron spin resonance

Pyrolytic carbon films were deposited on boron nitride substrates during plug-flow of a methane/argon gas mixture through a hot-wall tubular reactor at 100 kPa and 1100°C. Of particular interest is the time resolved development of chemical reactions within the free reactor volume, which is projected to the formed structures along the reactor axis. Spatially resolved electron spin resonance (ESR) is used to characterize the deposited films. The width and asymmetry of the ESR line varies monotonously along the reactor axis by more than one order of magnitude within 25 mm.

Up-squeezing of magma under tectonic stress.

That some volume of magma could be squeezed up from the magma reservoir triggering a volcanic eruption when compressional tectonic stress is strengthened by plate motion has been proposed as a possible explanation of successive occurrences of volcanic eruption and large earthquake. This idea, called the flask model, has been put forward in attempting to account for the relationship between the activities of Izu-Oshima volcano and the occurrences of great inter-plate earthquake associated with the Sagami trough off the Pacific coast of Central Japan. It is intended in this paper to examine whether such a model really works or not by taking the detailed configuration of magma reservoir into account. When a combination of parameter values usually accepted is assumed, it turns out that the volume of magma squeezed up by compressional tectonic stress may not be enough for triggering an eruption. It is therefore doubtful that a flask-model mechanism is actually working. Occasional eruptive activities of the volcano may rather be due to an increase in internal gas pressure in association with development of chemical reaction in the magma reservoir.

The influence of a grid‐generated turbulence on the development of chemical reactions

AbstractThe evolution of slow, irreversible, isothermal, second‐order chemical reactions between two nonpremixed species is experimentally studied in a field of quasiisotropic grid turbulence developing in a water tunnel. The experiments provide some basic data on the interaction between the turbulent mixing and the reaction, which tends to remove the mixed species.

Investigation of the flow and heat transfer of viscous reacting fluids in long tubes

Heat transfer and resistance in the case of laminar flow of inert gases and liquids in a circular tube were considered in [1–4], the justification of the use of boundary-layer type equations for investigating two-dimensional flows in tubes being provided in [4]. The flow of strongly viscous, chemically reacting fluids in an infinite tube has been investigated analytically and numerically in the case of a constant pressure gradient or constant flow rate of the fluid [5–8]. An analytic analysis of the flow of viscous reacting fluids in tubes of finite length was made in [9, 10]. However, by virtue of the averaging of the unknown functions over the volume of the tube in these investigations, the allowance for the finite length of the tube reduced to an analysis of the influence of the time the fluid remains in the tube on the thermal regime of the flow, and the details of the flow and the heat transfer in the initial section of the tube were not taken into account. In [11], the development of chemical reactions in displacement reactors were studied under the condition that a Poiseuille velocity profile is realized and the viscosity does not depend on the temperature or the concentration of the reactant; in [12], a study was made of the regimes of an adiabatic reactor of finite length, and in [13] of the flow regimes of reacting fluids in long tubes in the case of a constant flow rate. The aim of the present paper is to analyze analytically and numerically in the two-dimensional formulation the approach to the regimes of thermal and hydrodynamic stabilization in the case of the flow of viscous inert fluids and details of the flow of strongly viscous reacting fluids.

Nonequilibrium hypersonic flow of carbon dioxide gas over blunt bodies

The Navier-Stokes equations are used to investigate hypersonic flow of carbon dioxide gas over blunt bodies with allowance for nonequilibrium development of chemical reactions and vibrational relaxation of the CO2 molecules. The problem is solved by the method of stabilization by means of an implicit difference scheme that includes the use of Newton's iterative process. The results are given of calculations of the flow field, the convective heat flux, and the frictional stresses on the surface of blunt cones with spherical noses. The influence of admixtures on the flow field and the heat fluxes is investigated. The results of the calculations are compared with the locally self-similar solution for the neighborhood of the front stagnation point.

Effect of aluminum on the susceptibility of titanium to corrosion by salt

1. Commercially pure titanium is not prone to salt corrosion. Alloying the titanium with aluminum leads to salt corrosion, particularly when the aluminum content exceeds 4%. 2. The increase in the susceptibility of titanium alloys to salt corrosion with rise in the concentration of aluminum can be attributed to the following causes: hydrogenation of the metal in the zone of slow crack growth increases with the aluminum content; at temperatures at which salt corrosion occurs, aluminum reduces the solubility of hydrogen in titanium and increases its tendency to hydrogen brittleness; the aluminum is concentrated at the grain boundaries, and when its concentration at these boundaries exceeds 2%, α2 phase precipitates appear, which impede plastic deformation and promote the development of chemical reactions that take place with the liberation of hydrogen.