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Chemical reactions can lead to the expansion of the geomaterial because of the strong precipitation of minerals in the pores of the medium. The quantity and the variability of these reactions led to the development of several chemo-mechanical models. A generic chemo-poromechanical model is proposed to predict both the material degradation induced by various concrete pathologies and the environmental multi-factor impact on the macroscopic swelling. The model is based on the coupling between reactive transport (species diffusion and chemical reactions) and poromechanics. The mineralogy and the poromechanical properties are estimated by a hydration-micromechanics model which allows to consider the material effects. The main applications are dedicated to External Sulfate Attack and Delayed Ettringite Formation of cementitious material at mesoscale. The studies highlight the ability of the model to deal with complex and various phenomena such as coupling chemical reactions with calcium leaching, sulfate sorption and ettringite precipitation, and to consider their impact on the macroscopic expansion. Results also bring out the accuracy of the chemo-poromechanical model to simulate different swelling pathologies. The characteristic crack paths induced by differential strain, material impact, and swelling at the macroscopic scale, fit with experimental observations. [ABSTRACT FROM AUTHOR]

One-pot, three-component condensation of benzil/benzoin, substituted aromatic aldehydes, and ammonium acetate in an ethanol–water (1:1, v/v) solvent system using sulfated tin oxide catalyst under reflux condition afforded corresponding 2,4,5-triaryl-1H-imidazoles in excellent yield. The remarkable advantages offered by this method include green and reusable catalyst, mild reaction conditions, fast reaction rate, and excellent yield of products. This novel methodology maintains atom economy and an environmentally friendly approach. [ABSTRACT FROM AUTHOR]

With the aim of learning about the synergistic effect of a combination of (HOCH2)3P and Na2S2O4 for the bleaching of mechanical pulps, reactions of (HOCH2)3P (and its associated precursor, (HOCH2)4P+Cl−) with Na2S2O4 were studied in aqueous media under Ar and in air. The secondary phosphine (HOCH2)2PH is the major product in a 1:1 reaction of (HOCH2)3P and Na2S2O4 under Ar, the formaldehyde being removed in the form of HOCH2SO3Na and HOCH2SO2Na; the latter is Rongalite, itself an industrial bleaching agent. Significant amounts of the primary phosphine HOCH2PH2 are also seen. When the reaction is performed in air, the oxide (HOCH2)2P(O)H is the main product. Reaction of (HOCH2)4P+Cl− with Na2S2O4 (even under Ar) leads to solely the oxidation products: (HOCH2)3PO, (HOCH2)3PS, and (HOCH2)2P(O)OH. 31P{1H} and 1H NMR spectral data for secondary and primary (hydroxymethyl)phosphines and their oxidation products are reported for the first time. The toxicity of the primary and secondary phosphines is likely to curtail their use in commercial bleaching processes. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT [ABSTRACT FROM AUTHOR]

A simple, green, and very fast method for protection of aryl aldehydes as 1,1-diacetates promoted by cerium(IV) sulfate tetrahydrate, Ce(SO4)2·4H2O, as a novel inorganic solid acid catalyst at room temperature and under solvent-free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy workup, very short reaction times, high yields, and the absence of any volatile and hazardous organic solvents. [ABSTRACT FROM AUTHOR]

Aromatic aldehydes have been successfully converted into their corresponding dithioacetal, dithiolane and dithiane derivatives in excellent yields with thiol (benzyl thiol and thiophenol), 1,2-ethanedithiol and 1,3-propanedithiol using trichloroacetic acid in sodium dodecyl sulfate micelles. The same procedure is applicable to ketones, but they need more time to be converted into their thioacetals. [image omitted] [ABSTRACT FROM AUTHOR]

Al2O3-ZnO nanocomposite was synthesized by the sol-gel pyrrolysis method and characterized by SEM, TEM, EDAX analysis, XRD patterns, and Brunauer-Emmet-Teller (BET) specific surface area measurements. The optimized sample with uniform morphology and smallest particles sizes can be synthesized with 8%wt PVA, 4%wt Aluminum salt, 1%wt zinc salt, ethanol/water (60/40) as sol solvent, 2%wt sodium dodecyl sulfate (SDS) as additive, pH = 1, pyrrolysis temperature of 500°C, and pyrrolysis time of 5 h. The optimized Al2O3-ZnO nanocomposite consists of uniform nanoparticles with average diameter of 40 nm, 25.5 m2.g-1 specific surface area, and average pore diameter of 9.1 nm. [ABSTRACT FROM AUTHOR]

In this paper, the applicability of the ferron assay for the characterization of hydrolyzed Fe(III) produced in the Fenton's reaction system was investigated, and then the hydrolysis process of Fe(III) under typical Fenton's reaction conditions was compared with that in a normal ferric sulphate solution system, by applying the ferron assay method and the modified hydrolyticity, B*, a parameter that takes into account all the possibilities of base generation and reduction. It was found that the residual Fe(II) and H2O2 under normal Fenton's reaction conditions had little influence on the Fe(III)-ferron colorimetric reaction. Experimental results showed that the hydrolysis process of Fe(III) in the Fenton system was quite different from that in the ferric salt solution system. Under the same hydrolyticity, the hydrolysis rate of Fe(III) in the Fenton system was faster and more complicated than that in the ferric sulphate system, and the Fe(III) species produced in the Fenton system had a larger polymerization degree. With the increase in H2O2/Fe, Fea and Feb (the monomers and small polymeric Fe(III) species) increased gradually while Fec (the colloidal part) decreased, indicating that the increase in H2O2 had restrained the hydrolysis of Fe(III). This conclusion was also supported by the comparison of effective particulate diameters in the two systems. The fact that larger particles were produced with a shorter time in the Fenton system provided direct proof for the observation of the differences in the hydrolysis of Fe(III) in the two systems. The results of this study are useful for the possible utilization of the hydrolyzed Fe(III) produced in the Fenton's system for the removal of organic pollutants. [ABSTRACT FROM AUTHOR]

A novel reported method for preparation of the first thiophene thioglycosides via a one-pot reaction of sodium thiophenethiolate salts with 2,3,4,6-tetra-O-acetyl-α-D-gluco- and galactopyranosyl bromides has been studied. The sodium thiophenethiolate salts were prepared using sodium cyanoethylene thiolate salts. [ABSTRACT FROM AUTHOR]

The repair of the one electron oxidised form of a xanthine derivative by another xanthine derivative was studied by reacting aqueous binary mixtures of xanthine derivatives with sulphate radical anion (SO4-) and following the concentration of both compounds as a function of time. The relative behaviour observed enabled the establishment of a qualitative order of antioxidant capacities for the several xanthines studied in acidic and neutral media. The same order was confirmed quantitatively by measuring the reduction potentials of the xanthines by cyclic voltammetry. Theoretical DFT calculations were used to calculate the relative stabilities of the tautomers of each xanthine neutral radical. It was also demonstrated that the deprotonation of a xanthine radical cation never occurs from N1, unless no other possibility is available. At high pH values, it was possible to obtain the ESR spectra of the radical anions derived from 1-methylxanthine, 3-methylxanthine and xanthosine. The theoretical calculations also enabled the assignment of the ESR hyperfine coupling constants of the spectra of these radical anions. The coupling constants calculated are in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]

Cetyltrimethylammonium peroxodisulfate (CTA)2S2O8 was quantitatively prepared and used for the oxidation and deprotection of trimethylsilyl ethers to the corresponding carbonyl compounds in acetonitrile. Selective oxidation of allylic or benzylic trimethylsilyl ethers in the presence of saturated alkyl trimethylsilyl ethers were also achieved. This new reagent is more efficient and has several advantages over similar oxidants in terms of the amount of oxidant, short reaction time, simple work up, and high yield. [ABSTRACT FROM AUTHOR]

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media has been investigated by a constant interfacial cell with laminar flow. Studies of interfacial tension and effects of the stirring rate, temperature, and specific interfacial area on mass transfer rate show that the most probable reaction zone takes place at the liquid-liquid interface. According to the experimental data correlated as a function of the concentration of the relevant species involved in the extraction reaction, the rate equation of extracting thorium has been obtained as follows: [image omitted] The kinetic mechanism of the extraction process is proposed taking an interfacial chemical reaction as the rate-determining step of the overall reactions. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide and the persulfate dianion both undergo photochemical cleavage reactions in aqueous solution, creating a pair of hydroxyl (HO•) or sulfate anion ( [image omitted]) radicals, respectively. These radicals can abstract H-atoms or undergo electron transfer reactions in the presence of organic substrates, leading to carbon-centred free radicals. The chemically induced electron spin polarization (CIDEP) pattern created during time-resolved electron paramagnetic resonance (TREPR) experiments involving these species is always observed to be low field emissive/high field absorptive (E/A), coupled with net absorption. There are numerous suggestions in the literature regarding the origin of the E/A* pattern: Contributions from thermally equilibrated radicals, concentration-dependent spin relaxation, or the result of a spin-selective electron transfer reaction to create closed shell ionic structures. Here, it is proposed that E/A and E/A* contributions arise from two different F-pairs that must be present in these solutions. Examples are presented and the origin of the effect is explained in terms of well-established CIDEP theories for freely diffusing radical pairs. The importance of the A* contribution is discussed with regard to the recently reported observation of peroxyl radicals from addition of oxygen to amino acid radicals at room temperature. [ABSTRACT FROM AUTHOR]

Novel 2 '-C-methyl-cyclopropyl-fused carbocyclic nucleosides as potential anti-HCV agents were stereoselectively synthesized, utilizing regioselective cleavage of the isopropylidene group and cyclic sulfate chemistry as key steps. [ABSTRACT FROM AUTHOR]

The structure and activity of RNase A in sodium dodecyl sulphate solutions were investigated at 25.0±0.1 and pH 7.00. The results show that with increasing sodium dodecyl sulphate concentration, the structure of RNase A is collapsed gradually, however, the activity of RNase A is first increased and then decreased. This is mainly due to the different effect of SDS at different SDS concentration. [ABSTRACT FROM AUTHOR]

The focus of this study was on sulfate-rich wastewater treatment in a novel anaerobic / micro-aerobic bioreactor system. The system was composed of an upward-flow anaerobic sludge blanket (UASB) reactor and a floated bed micro-aerobic reactor, which was packed with elastic porous carriers and was controlled in a situation of dissolved oxygen below 0.5 mg l-1. The floated bed micro-aerobic reactor was developed for accumulating a higher amount of biomass in carriers with a short hydraulic retention time (HRT) for biological oxidation of hydrogen sulfide to elemental sulfur. During long-term steady state operation, experimental results showed that an average of 70±6% of sulfate was transformed to hydrogen sulfide in UASB reactor. Moreover, the overwhelming majority of sulfide was oxidized to elemental sulfur and sulfate in micro-aerobic reactor; and the recirculation of effluent to UASB reactor reduced effectively the degree of inhibition caused by sulfate-rich wastewater. In UASB reactor, chemical oxygen demand (COD) removal efficiency increased with COD loading, in contrast, the performance of sulfate removal decreased with the increase in sulfate loading in a range of 1.0-1.75 kg SO42- m-3 d-1. In micro-aerobic reactor, sulfide was removed almost completely under the operation of HRT 2.8 h. Furthermore, experimental results of continuous operations revealed that oxidation-reduction potential (ORP) was an adequate parameter for controlling biological oxidation of sulfide. When ORP was regulated in a lower range of -250 to -300 mV, the amount of regenerated sulfate was reduced significantly in micro-aerobic reactor. [ABSTRACT FROM AUTHOR]

The environmentally friendly condensation 3-methyl-l-phenyl-5-pyrazolone or 3-methyl-1H-5-pyrazolone with aromatic and aliphatic aldehydes was performed in water at refluxing temperature for 1 h using sodium dodecyl sulfate (SDS) as the surfactant catalyst (5 mol%), giving 4,4'-alkylmethylene-bis(3-methyl-5-pyrazolones) in 78.3%~92.1% yields. [ABSTRACT FROM AUTHOR]

The thermal reactions in the mixtures of hydroxylapatite or fluorapatite and (NH4)2SO4up to 500°C were studied with the purpose of elaborating the conditions of obtaining calcium–ammonium cyclophosphate that could be used as fertilizer. Thermal analysis with a simultaneous FTIR analysis of the evolved gases as well as the analyses of chemical and phase composition of solid products were performed. The thermal changes in the mixtures could be divided into three steps: (1) decomposition of (NH4)2SO4and reactions of apatite with these products at 250–420°C, (2) calcium ammonium polyphosphate formation at 290–450°C, and (3) reaction of CaSO4with CaNH4P3O9at 320–500°C. Higher concentrations of NH3in the gas phase promote the formation of CaNH4P3O9and increase its stability. Calcination at temperatures above 350°C causes decomposition of CaNH4P3O9with a decrease in the content of water-soluble phosphorus and evolvement of SO2. [ABSTRACT FROM AUTHOR]

Cyclic sulfates of carbohydrates provide excellent synthons for the preparation of isodeoxyuridines through direct nucleophilic substitution reactions. These substitution reactions have exceptional regioselectivity. The products of the reactions served as key precursors for the synthesis of 5-substituted isodeoxyuridines via the Stille and Heck coupling reactions. Interestingly, unprotected nucleosides could be used in these metal-mediated functionalizations. The methodologies are general and allow ready access to a variety of C-5 functionalized isomeric deoxyuridines, but also have the potential to be extended to other nucleoside analogs. [ABSTRACT FROM AUTHOR]

Mono(thio)substituted dienes 1a-1b gave compounds 3a-c and 5d-g with piperazine and piperidine derivatives in dichloromethane. Compounds 8 , 9 , and 10 were obtained from the reactions of perchlorobutadiene ( 6 ) with 1,4-butanedithiol ( 7 ) in ethanol in the presence of sodium hydroxide. Compounds 12a-b , 13a-b were obtained from the reactions of perchlorobutadiene ( 6 ) with allylmercaptan (CH 2 =CH--CH 2 --SH) and mercaptoethanol (HO--CH 2 --CH 2 --SH). [ABSTRACT FROM AUTHOR]