The ROBIA program for predicting organic reactivity

A program to predict organic reactions, ROBIA, has been developed. It achieves reaction prediction on the basis of coded rules and molecular modeling calculations, generating possible transition states, intermediates, and products given the starting material and reaction conditions. The program generates all possible reaction pathways, on the basis of the selected transformations within its database, and evaluates them selecting the most feasible ones. The program has been successfully tested against several examples.     

A possible construction of chemical reaction networks

The chemical reaction networks and the sequence networks represent the pathways of a complex chemical process. In order to study the pathways separately the systematization of the elementary processes included in the possible mechanism is inevitable.This systematization was realized by a special procedure based on linear algebraic methods and enabled us to select the corresponding processes from the possible mechanism. The efficiency of the procedure has been illustrated by its application to the liquid phase oxidation of ethylbenzene and the elementary processes have been selected using a computer program.     

Dimephosphon,a new Phosphorus-Containing Medical Drug for Treatment of Acidosis: Chemistry and Technology

Abstract

Medical drug dimephosphon-dimethyl 1,l-dimethyl-3-oxobutnylphosphonate was created as a result of chemical and biological investigations of low-toxic organophosphorus compounds. This drug was selected from a number of acyclic transformation products of 1,2-oxyphospholene derivatives. A technology was worked out which is based on the Pudovik reaction and transformed into the continuous process. For this process an original continuous flow reactor has been created.     

An investigation of the potential uses of iodine monochloride as a titrant in thermometric titrimetry

An investigation has been made of the potential uses of iodine monochloride as a titrant in thermometric titrimetry. A series of substances, inorganic and organic, has been selected so that a range of stoichiometries and of various types of reaction products result from the oxidation. It has been found to be necessary to prevent the formation of iodine formed by oxidation of the iodide produced by the reduction of iodine monochloride. This is successfully accomplished by using mercury(II) to mask the iodide in a mercury(II)-iodide complex. However, the evolution of gaseous products tends to give curvature of the enthalpogram near the equivalence point and the method is not recommended for the determination of compounds such as thiosemicarbazide. For many other systems, iodine monochloride used in the presence of mercury(II) has analytical potential as a thermometric titrant.     

Tertiary recycling of commingled polymer waste over commercial FCC equilibrium catalysts for producing hydrocarbons

A mixture of post-consumer polymer waste (PE/PP/PS) was pyrolysed over cracking catalysts using a fluidising reaction system similar to the FCC process operating isothermally at ambient pressure. Greater product selectivity was observed with a commercial FCC equilibrium catalyst (FCC-E1) with about 53 wt% olefin products in the C₃-C₆ range. Experiments carried out with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A kinetic model based on a lumping reaction scheme for the observed products and catalyst coking behaviours has been investigated. The model gave a good representation of experiment results. This model provides the benefits of lumping product selectivity, in each reaction step, in relation to the performance of the catalyst used and particle size selected as well as the effect of operation conditions, such as rate of fluidising gas and reaction temperature. It is demonstrated that under appropriate reaction temperatures and suitable catalysts can have the ability to control both the product yield and product distribution from polymer degradation, and can potentially lead to a cheaper process with more valuable products.     

Solution and solid state structure and tautomerism of azo coupled enaminone derivatives of benzoylacetone

The reaction of 4-substituted benzenediazonium tetrafluoroborates with 3-amino-1-phenylbut-2-en-1-one, 4-amino-4-phenylbut-3-en-2-one and their N-aryl derivatives 1a-1g has been used to prepare the respective azo coupling products i.e. compounds 2-5 from enaminone 1a, compounds 6-9 from enaminone 1c, compound 10 from enaminone 1d, compound 11 from enaminone 1e, compounds 12, 13 from enaminone 1f, compounds 14, 15 from enaminone 1b and compound 16 from enaminone 1g. Tautomerism of the azo coupling products prepared has been investigated in CDCl3 solutions by means of 1H, 13C and 15N NMR spectra. Crystal structures of selected products have also been investigated by means of X-ray diffraction.     

Novel one-pot three-step reaction using supported reagents system: synthesis of 2-aminothiazoles

One-pot tandem three-step reaction has been developed by using supported reagents system. The synthesis of 2-aminothiazoles was selected for confirming the effectiveness of the method using supported reagents system. One-pot three-step reaction effectively proceeded, and the yield of the products is higher than that in step-wise process.     

A study of the ethene-ozone reaction with photoelectron spectroscopy: measurement of product branching ratios and atmospheric implications

The ozone-ethene reaction has been investigated at low pressure in a flow-tube interfaced to a u.v. photoelectron spectrometer. Photoelectron spectra recorded as a function of reaction time have been used to estimate partial pressures of the reagents and products, using photoionization cross-sections for selected photoelectron bands of the reagents and products, which have been measured separately. Product yields compare favourably with results of other studies, and the production of oxygen and acetaldehyde have been measured as a function of time for the first time. A reaction scheme developed for the ozone-ethene reaction has been used to simulate the reagents and products as a function of time. The results obtained are in good agreement with the experimental measurements. For each of the observed products, the simulations allow the main reaction (or reactions) for production of that product to be established. The product yields have been used in a global model to estimate their global annual emissions in the atmosphere. Of particular interest are the calculated global annual emissions of formaldehyde (0.96 ± 0.10 Tg) and formic acid, (0.05 ± 0.01 Tg) which are estimated as 0.04% and 0.7% of the total annual emission respectively.     

Rapid determination of parabens in personal care products by stable isotope GC‐MS/MS with dynamic selected reaction monitoring

In this study, a rapid and sensitive analytical method for the determination of methyl‐, ethyl‐, propyl‐, and butyl esters of para‐hydroxy benzoic acid (parabens) in personal care products was developed and fully validated. Test portions were extracted with methanol followed by vortexing, sonication, centrifugation, and filtration without derivatization. The four parabens were quantified by GC‐MS/MS in the electron ionization mode. Four corresponding isotopically labeled parabens were selected as internal standards, which were added at the beginning of the sample preparation and used to correct for recovery and matrix effects. Sensitivity, extraction efficiency, and recovery of the respective analytes were evaluated. The coefficients of determination (r²) were all greater than 0.995 for the four parabens investigated. The recoveries ranged from 97 to 107% at three spiked levels and a one‐time (single) extraction efficiency greater than 97% was obtained. This method has been applied to screen 26 personal care products. This is the first time that a unique GC‐MS/MS method with dynamic selected reaction monitoring and confirmation of analytes has been used to determine these parabens in cosmetic personal care products.     

Tetraethylenepentamine-directed controllable synthesis of wurtzite ZnSe nanostructures with tunable morphology

A novel tetraethylenepentamine (TEPA)-directed method has been successfully developed for the controlled synthesis of ZnSe particles with distinctive morphologies, including nanobelts, nanowires, and hierarchically solid/hollow spheres. These structures, self-assembled from nanobelts and nanorods, have been synthesized by adjusting the reaction parameters, such as the solvent composition, reaction temperature, and the aging time. Results reveal that the volume ratio of H2O and TEPA plays a crucial role in the final morphology of ZnSe products. The mechanisms of phase formation and morphology control of ZnSe particles are proposed and discussed in detail. The products have been characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), selected area electron diffraction, high-resolution TEM, Raman spectra and luminescence spectroscopy. The as-prepared ZnSe nanoparticles display shape- and size-dependent photoluminescent optical properties. This is the first time to report preparation of complex hollow structures of ZnSe crystals with hierarchy through a simple solution-based route. This synthetic route is designed to exploit a new H2O/TEPA/N2H4H2O system possibly for the preparation of other semiconductor nanomaterials.     

Separation of group five elements by reversed-phase chromatography

A chemical separation method based on reversed-phase chromatography has been developed to separate the group five elements from the reaction products produced in the bombardment of ²⁴³Am with ⁴⁸Ca ions. Decontamination factors on the order of 10⁶ were achieved for group-three elements such as americium, and 10⁷ or more for selected reaction products as measured by gamma-ray spectrometry pre-and post-chemistry. Details of the chemical separation scheme are discussed and compared to previously reported results.     

Site-selective, cleavable linkers: quality control and the characterization of small molecules on microelectrode arrays

A "safety-catch" linker strategy has been used to release a portion of the products of a Diels-Alder reaction conducted on a microelectrode array for characterization of stereochemistry. The attachment and cleavage of organic compounds from the surface of selected electrodes in the array can be accomplished by site-selective generation of base or acid at the electrode. It was found that the surface of the array had a minor influence on the stereochemistry of the Diels-Alder reaction, leading to slightly more of the exo-product relative to a similar solution-phase reaction.     

Efficient synthesis of highly functionalized tetrahydropyridopyrimidines by a novel three-component coupling reaction

We report the development of a novel three-component coupling reaction (3CC) for the synthesis of alkoxy tetrahydropyridopyrimidines. Systematic optimization of reaction parameters identified 3CC conditions tolerant of a wide array of functionality at all three sites of diversity, providing densely functionalized products in moderate to excellent yields. The newly developed chemistry has since been applied to the lead optimization process on a novel drug discovery program, facilitating rapid compound advancement.     

Efficient and facile strategy to substituted 2-aminothiazoles via ring opening of α-nitroepoxides

A novel and efficient reaction has been developed to synthesize a set of substituted 2-aminothiazoles from α-nitroepoxides and ammonium thiocyanate. This reaction could proceed smoothly at mild condition, to afford products for a wide range of substrates with good to excellent yields. A possible mechanism has also been proposed.     

Peroxyoxalate Photoinduced Chemiluminescence Detection of Norfloxacin in Pharmaceutical Products by Flow Injection Analysis

A new method for the determination of norfloxacin by flow injection analysis based on photoinduced chemiluminescence detection is proposed. We have selected the peroxyoxalate (PO) reaction based on the possibility of detecting fluorescent products derived from a photochemically induced decomposition of norfloxacin, observing high signal when the derivative participates in the reaction. A FIA device, with two-injection valves for the introduction of both the PO and the photodecomposed analyte solutions in the flow system, has been used, avoiding the problems arising from the use of organic solvents. The method was applied to the monitoring of norfloxacin in pharmaceuticals.     

Base-Assisted Conversion of Protonated D-Fructose to 5-HMF: Searching for Gas-Phase Green Models

A gas-phase investigation of the D -fructose dehydration reaction in the presence of base has been performed by the joint application of mass spectrometric techniques and theoretical calculations. Protonated addition products of D -fructose and base were generated in the gas phase by electrospray ionization using several bases of different proton affinity. The intermediates, products and decomposition channels were investigated by ion trap mass spectrometry. Electronic structure calculations allowed the identification of the ionic intermediates and products of a selected system containing NH₃, helping to rationalize the observed reaction pathways. The obtained results show that the final product, the protonated 5-hydroxymethyl-2-furaldheyde [5-HMF]H⁺, is better formed using selected bases and only if these remain clustered until the end of the dehydration process.     

Reaction of H-Phosphonate Diesters with Trityl Halides

Abstract

A study on the reaction of H-phosphonate diesten with trityl halides under different reaction conditions has been performed. The reactions were evaluated using 31P NMR spectroscopy. For the study we selected simple H-phosphonate diesters, i.r. diphenyl H-phosphonate and diethyl H-phosphonate. Depending on the reaction conditions used the products obtained differed substantially. Formation of C-phosphonate 1 vs 2 depended primarily on the kind of trityl derivative used for the reaction.     

Catalytic determination of ultra trace amounts of vanadium with detection by linear sweep voltammetry

Vanadium has a very strong catalytic effect on the bromate oxidation of gallocyanine at pH of 4.0. The oxidation product of gallocyanine exhibit a voltammetric wave at + 0.10 V vs. Ag/AgCl reference electrode in 0.10 mol/l KNO₃ medium. The linear scan voltammetric behaviour of the reaction products at HMDE has been studied and selected as the indicator component for the reaction. A detection limit of 0.05 ng/ml and calibration graph from 0.30–200.00 ng/ml vanadium were obtained. Vanadium in water and gasoline samples was determined by this method, with satisfactory results.