HCl Reaction Research Articles

OH + HCl Reaction on the Surface of Ice: An Ab Initio Molecular Dynamics Study.

We have investigated the OH + HCl reaction on the surface of ice using Born-Oppenheimer molecular dynamics (BOMD) simulation. The present work revealed that the OH + HCl reaction becomes ∼1 order of magnitude faster on the ice surface compared to the bare reaction. The BOMD simulation also indicates that the Cl radical formed on the ice surface through the title reaction can form two hydrogen bonds at a time with the water molecules present on the ice surface; hence, the Cl radical cannot escape from the ice surface easily.

Qualitative and quantitative analysis of some co-existing colorants in some hard candies

Based on the results of qualitative analysis, a simple and accurate acidity-controlled absorption spectroscopy method for the determination of certain coexisting pigments in commercial candies is established. Using a Tris−HCl (pH 3.6) reaction medium, brilliant blue (BRI) and tartrazine (TAR) react with malachite green (MAG); tartrazine and sunset yellow (SUN) react with brilliant green (BRG); and curcumin (CUR) and sunset yellow react with crystal violet (CRY). They all form binary ion association complexes. Their linear range are 0.06–21.4 mg/L (BRI-MAG, 628 nm), 0.06–11.8 mg/L (TAR-MAG, 436 nm), 0.04–11.8 mg/L (TAR-BRG, 425 nm), 0.04–9.1 mg/L (SUN-BRG, 502 nm), 0.03–10.0 mg/L (SUN-CRY, 484 nm), and 0.03–11.1 mg /L (CUR-CRY, 390 nm), respectively. The detection limit and quantification limit of each system are 0.041 mg/L and 0.71 mg/kg (MAG system), 0.035 mg/L and 0.61 mg/kg (BRG system), and 0.030 mg/L and 0.52 mg/kg (CRY violet system), respectively. This method is simple, rapid, accurate, sensitive and selective. The coexisting pigments curcumin, tartrazine, sunset yellow, and brilliant blue can be determined without pigment separation and complex mathematical model. It has been used in the determination of actual candies with satisfactory results.

Strong non-Arrhenius behavior at low temperatures in the OH + HCl → H2O + Cl reaction due to resonance induced quantum tunneling.

The OH + HCl → H2O + Cl reaction releases Cl atoms, which can catalyze the ozone destruction reaction in the stratosphere. The measured rate coefficients for the reaction deviate substantially from the Arrhenius limit at low temperatures and become essentially independent of temperature when T < 250 K, apparently due to quantum tunneling; however, the nature of the quantum tunneling is unknown. Here, we report a time-dependent wave packet study of the reactions on two newly constructed potential energy surfaces. It is found that the OH + HCl reaction possesses many Feshbach resonances trapped in a bending/torsion excited vibrational adiabatic potential well in the entrance channel due to hydrogen bond interaction. These resonance states greatly induce quantum tunneling of a hydrogen atom through the reaction barrier, causing the reaction rates to deviate substantially from Arrhenius behavior at low temperature, as observed experimentally.

The effect of (H2O)n (n = 1-3) clusters on the reaction of HONO with HCl: a mechanistic and kinetic study.

The reaction between HONO and HCl is a possible pathway for the generation of ClNO, which is prone to photolyze, produce chlorine radicals, and accelerate the oxidation of tropospheric VOCs. Current experimental and theoretical studies have significant differences in rate constants under similar conditions. This study aims to examine the reasons for this difference. In this study, the effects of a single water molecule, water dimer, water trimer, excess HCl and excess HONO on the reaction mechanism of HONO + HCl were studied at the CCSD(T)/aug-cc-pVTZ//M06-2X/6-311+G(2df,2p) level and the rate constants of each reaction channel were calculated. Our results showed that the reaction potential barrier of HONO with HCl was the lowest only when the water dimer was present, and the reaction rate constants were close to the experimental results, and both the cis-HONO⋯(H2O)2 + HCl and the trans-HONO⋯(H2O)2 + HCl reaction paths are likely to occur. We think that the reason for the inconsistency between experimental and theoretical results is that the water dimer is involved in the reaction in experiments.

Insight into generalized local softness based on ABEEM‐σπ method: Electrophilic additions to alkenes

AbstractAccording to the local hard‐soft acid – base (HSAB) principle, the generalized local softness has been investigated based on the electrophilic reactions of H2O, HF, HCl and HBr to alkenes, and the effect of the softness on the chemical reactivity was studied in terms of the ab initio and atom‐bond electronegativity equalization method plus σπ (ABEEM‐σπ) method. Studies show that the finite difference approximation with ab initio method cannot always be used to predict the regioselectivity of the investigated reactions in terms of the local HSAB principle. But ABEEM‐σπ model could well describe chemical reactivity according to the local HSAB principle. A significant characteristic of the ABEEM‐σπ method is that the double bond is explicitly considered and partitioned. The square sums of differences of the local softness of the reaction center atoms, that is, Δs, or ΔSG with the generalized local softness and with the electronegativity, have been studied on the considered electrophilic additions. Studies indicate that ΔSG can be utilized not only to predict regioselectivity rules but also to rationalize the chemical reactivity of these addition reactions, and the generalized local softness is more suitable for the investigation of chemical reactivity between two chemical species.

Study of dynamics and mechanism of HCl, SO2, or NO removal by MnO2/Mg–Al layered double hydroxide

The gas exhaust generated by waste incinerators contains toxic acid gases such as HCl, SO2, and NOx, which require appropriate treatment following their release. Although several methods exist for this purpose, they have various drawbacks. Thus, toward the search for a new removal method, the ability of Mg–Al layered double hydroxide (Mg–Al LDH) to eliminate HCl, SO2, and NO gases from simulated exhaust gas was examined. In addition, the impact of the amount of LDH employed was investigated in terms of the toxic gas removal efficiencies and process temperature. Furthermore, the mechanism of removing HCl, SO2, and NO by MnO2/Mg–Al LDH was considered. More specifically, HCl removal proceeded mainly by the reaction of HCl with the CO32− and OH− species present between the Mg-Al LDH layers, while that of SO2 took place through the adsorption of SO2 onto the LDH and MnO2 surfaces. Moreover, NO was removed through the oxidation of NO to NO2 by MnO2, followed by the reaction of NO2 with the CO32− and OH− species present between the Mg–Al LDH layers. These results are expected to help pave the way for the use of Mg–Al LDH to remove toxic acid gases from the gas exhausts of waste incinerators, thereby addressing the various issues related to the use of current technologies.

Chemical Evolution of the Exceptional Arctic Stratospheric Winter 2019/2020 Compared to Previous Arctic and Antarctic Winters

AbstractThe winter 2019/2020 showed the lowest ozone mixing ratios ever observed in the Arctic winter stratosphere. It was the coldest Arctic stratospheric winter on record and was characterized by an unusually strong and long‐lasting polar vortex. We study the chemical evolution and ozone depletion in the winter 2019/2020 using the global Chemistry and Transport Model ATLAS. We examine whether the chemical processes in 2019/2020 are more characteristic of typical conditions in Antarctic winters or in average Arctic winters. Model runs for the winter 2019/2020 are compared to simulations of the Arctic winters 2004/2005, 2009/2010, and 2010/2011 and of the Antarctic winters 2006 and 2011, to assess differences in chemical evolution in winters with different meteorological conditions. In some respects, the winter 2019/2020 (and also the winter 2010/2011) was a hybrid between Arctic and Antarctic conditions, for example, with respect to the fraction of chlorine deactivation into HCl versus ClONO2, the amount of denitrification, and the importance of the heterogeneous HOCl + HCl reaction for chlorine activation. The pronounced ozone minimum of less than 0.2 ppm at about 450 K potential temperature that was observed in about 20% of the polar vortex area in 2019/2020 was caused by exceptionally long periods in the history of these air masses with low temperatures in sunlight. Based on a simple extrapolation of observed loss rates, only an additional 21–46 h spent below the upper temperature limit for polar stratospheric cloud formation and in sunlight would have been necessary to reduce ozone to near zero values (0.05 ppm) in these parts of the vortex.

Insertion products in the reaction of carbonyl oxide Criegee intermediates with acids: Chloro(hydroperoxy)methane formation from reaction of CH2OO with HCl and DCl

The reactions of carbonyl oxide Criegee intermediates with acids proceed predominantly by an insertion mechanism. We characterise the products from one of the simplest reactions of carbonyl oxides with inorganic acids, CH2OO + hydrogen chloride, which occurs via a 1,2-insertion in the H–Cl bond. Reactions of both HCl and DCl isotopologues yield product signal at the mass of the insertion product chloro(hydroperoxy)methane and a dissociative ionisation peak at the mass of the protonated (or deuteronated) Criegee intermediate. The isotopic composition of the insertion product has been measured for reaction mixtures where both HCl isotopologues are present, and the H/D ratio of the product is consistently higher (by a factor of 1.6 ± 0.3) than that of the reactants. This isotope selectivity in the products has smaller uncertainty than the ratio of measured rate coefficients and suggests a normal (k H > k D) kinetic isotope effect in the reaction. Theoretical kinetics calculations predict a small normal kinetic isotope effect for the overall reaction (k H / k D = 1.35 at 20 Torr N2 and k H / k D = 1.2 at 1 atm N2) but predict a substantial inverse kinetic isotope effect (k D > k H) for the stabilisation fraction, in disagreement with the experimental observation.

Valorization of decationized newsprint to levulinic acid

As of today, most chemical products are fossil-based. The environmental concerns of fossil resources due to their constant misuse have led to the exploration of bio-based alternatives. Biomass comprising industrial and municipal wastes, agricultural residues, forest residues, and natural herbaceous plants can favorably replace fossil fuel to produce chemicals. In this study, softwood and hardwood pulps were used to synthesize levulinic acid. Prior to a dilute acid hydrolysis step, the wood pulps were decationized overnight with 0.2 M HCl. The effects of the major reaction conditions including reaction temperature, time, and HCl concentration on the yield of levulinic acid was studied via a central composite design. Levulinic acid yields from softwood and hardwood pulps reached 50.30 and 68.85 mol%, respectively, at optimum reaction conditions. When newsprints were tested using the optimized parameters for softwood and hardwood conversion, levulinic acid yields of 66.25 and 79.65 mol% were obtained, respectively. A kinetic model was developed to predict the yields of glucose, hydroxymethylfurfural, and levulinic acid from the HCl-pretreated newsprint. The analysis of the kinetic parameters and the results of the response surface methodology experiments provided optimized conditions for levulinic acid production.

Influence of acidic type on nanostructures and electrochemical performance of polyaniline for flexible supercapacitors and improved performance based on 3D honeycomb-like nanosheet by doping HPF6 acid

Designing and preparing polyaniline (PANI)-based flexible electrode materials with special nanostructure hold critical promise as capacitive materials. Here, the PANIs were synthesized in HCl, H2SO4, phytic acid and HPF6 reaction systems with the same concentration via fast microwave-assisted chemical polymerization. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-vis absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS) were conducted to characterize their nanostructures and chemical compositions. Results reveal an apparent influence of acidic types on PANI morphology and nanostructures. The HPF6-doped PANI/carbon cloth (F-PANI/CC) show the morphology of 3D honeycomb-like nanosheets and highly ordered phenazine-like oligomeric structure as well as higher homogeneous protonation of PANI backbones on the substrate of carbon cloth (CC). These main features favor the formation of rich electron centers, density of electric charges, and better contact and reaction between PANI materials and electrolyte. As a consequence, the assembled F-PANI/CC-based symmetric solid-state supercapacitor exhibits favorable electrochemical performance with a maximum energy density of 32.6 Wh kg−1 and a maximum power density of 1693 W kg−1 at a voltage window of 1.0 V compared with other PANI electrode materials. This work would inspire the HPF6-doped PANI electrode materials for high-performance flexible supercapacitors.

Sulphide Globules in a Porcellanite–Buchite Composite Xenolith from Stromboli Volcano (Aeolian Islands, Southern Italy): Products of Open-System Igneous Pyrometamorphism

Pyrometamorphism is the highest temperature end-member of the sanidinite facies (high-temperature, low-pressure contact metamorphism) and comprises both subsolidus and partial melting reactions which may locally lead to cryptocrystalline-glassy rocks (i.e., porcellanites and buchites). A wide range of pyrometamorphic ejecta, with different protoliths from Stromboli volcano, have been investigated over the last two decades. Among these, a heterogeneous (composite) glassy sample (B1) containing intimately mingled porcellanite and buchite lithotypes was selected to be studied through new FESEM–EDX and QEMSCAN™ mineral mapping investigations, coupled with the already available bulk rock composition data. This xenolith was chosen because of the unique and intriguing presence of abundant Cu–Fe sulphide globules within the buchite glass in contrast with the well-known general absence of sulphides in Stromboli basalts or their subvolcanic counterparts (dolerites) due to the oxygen fugacity of NNO + 0.5–NNO + 1 (or slightly lower) during magma crystallization. The investigated sample was ejected during the Stromboli paroxysm of 5 April 2003 when low porphyritic (LP) and high porphyritic (HP) basalts were erupted together. Both types of magmas are present as coatings of the porcellanite–buchite sample and were responsible for the last syn-eruptive xenoliths’s rim made of a thin crystalline-glassy selvage. The complex petrogenetic history of the B1 pyrometamorphic xenolith is tentatively explained in the framework of the shallow subvolcanic processes and vent system dynamics occurred shortly before (January–March 2003) the 5 April 2003 paroxysm. A multistep petrogenesis is proposed to account for the unique occurrence of sulphide globules in this composite pyrometamorphic xenolith. The initial stage is the pyrometamorphism of an already hydrothermally leached extrusive/subvolcanic vent system wall rock within the shallow volcano edifice. Successively, fragments of this wall rock were subject to further heating by continuous gas flux and interaction with Stromboli HP basalt at temperatures above 1000 °C to partially melt the xenolith. This is an open system process involving continuous exchange of volatile components between the gas flux and the evolving silicate melt. It is suggested that the reaction of plagioclase and ferromagnesian phenocrysts with SO2 and HCl from the volcanic gas during diffusion into the melt led to the formation of molecular CaCl in the melt, which then was released to the general gas flux. Sulphide formation is the consequence of the reaction of HCl dissolved into the melt from the gas phase, resulting in the release of H2 into the melt and lowering of fO2 driving reduction of the dissolved SO2.

Morphological features of the soil cover of slope lands in the south of the Volga uplands within the urban landscapes of Volgograd

The paper deals with morphological properties of agrogenically transformed chestnut soils of slope lands in the south of the Volga upland within the urban landscape of Volgograd. It is established that as a result of agrogenesis, erosion, land use change, as well as of agroforestry reclamation measures performed, both anthropogenic deeply transformed and postagrogenic soils have been formed. The greatest changes under the influence of agrogenesis are noted in morphological structure of profiles. Agrogenesis results in degradation of soils involved in active agricultural use due to intensified sheet and rill erosion. In eroded soils there is noticed a decrease in the thickness of agrohumic layer, formation of furrow bottom compaction and changes in structure. Their characteristic feature is the presence on the surface of a homogeneous agro-abraded horizon with lumpy structure, in the lower part of which secondary carbonates inherited from the carbonate horizon and resulted from deep plowing may occur. Soils slightly exposed and not exposed to erosion processes have an agrohumus horizon on the surface, which depending on soil tillage can have thickness from 19 to 36 cm. At present, the annual agricultural practices at the plot include mowing of weeds and disk plowing to 20 cm depth. Earlier moldboard plowing to 40 cm depth was performed. All agrogenically-modified soils are characterized by HCl reaction with carbonates from the surface. Carbonate accumulations in agrogenic soils, as a rule, have a segregated form that indicates rapid summer drying of the profile and short period of soil solutions migration. Upper boundary of accumulative-carbonate horizons of agrogenic soils on the average is at 42 cm depth. Such occurrence of carbonate horizons in general is typical both of natural non-eroded soils of dry-steppe zone and of soils involved in agricultural land use. Under forest plantations the original chestnut soils were transformed into turbated agrozems due to deep ameliorative cultivation preceded planting of woody and shrub vegetation. Soil preparation practices applied before tree species planting resulted in transformation of original chestnut soils into turbated agrozems, which is due to deep (up to 60 cm) soil reclamation. The forest belt, being a “barrier” between the field parts, contributed to the formation of a stratified small horizon (trait) of 10 cm thickness for more than 70 years due to the constant inflow of fine-grained soil and decay of leaf and herbaceous debris.

Utilization of N-bromosuccinimide for the sensitive spectrophotometric determination of pipazethate HCl as antitussive drug in pure and dosage forms

Three simple, sensitive, precise, reproducible and validated spectrophotometric methods have been developed for the quantification of pipazethate HCl as antitussive drug in pure and dosage forms. The methods are based on utilization of N-bromosuccinimide as an oxidant and three dyes, amaranth, methylene blue, and indigo carmine, as auxiliary reagents. The proposed methods are based on oxidation reaction of pipazethate HCl with a known excess of N-bromosuccinimide in acid medium, followed by determination of unreacted N-bromosuccinimide by the reaction with a fixed amount of dyes, amaranth, methylene blue, and indigo carmine followed by the measurement of the absorbance at 520, 663 and 610nm, respectively. The optimization of the reaction conditions was investigated. Under the optimum conditions, linear relationships with good correlation coefficients (0.9998-0.9999) were found over the concentration ranges of 0.3-9.0, 0.5-12 and 0.5-10μgmL-1 with a limit of detection (LOD) of 0.1, 0.15 and 0.15μgmL-1 using amaranth, methylene blue, and indigo carmine methods, respectively. Intra-day and inter-day accuracy and precision of the methods have been evaluated. No interference was observed from the common tablet excipients. The developed methods were validated in accordance with ICH guidelines and successfully applied to the analysis of pipazethate HCl in dosage forms with good accuracy and precision. The reliability of the methods was further ascertained by performing recovery studies via the standard addition method. Statistical comparison of the results obtained by applying the proposed methods with those of the reported method by applying Student's t-test and variance ratio F-test at the 95% confidence level revealed good agreement and indicates no significant difference in accuracy and precision.

Leaching characteristics of an iron-rich siltation pond waste and its viability in indirect carbon sequestration

ABSTRACT An iron-rich siltation pond waste from a nickel mining site was used as the starting material for indirect carbonation. Iron-leaching experiments were conducted on the mining waste, using HCl as the leaching agent at varying HCl concentrations, reaction times, and reaction temperatures. It was found that the extraction efficiency of iron (EEI) increased when a more concentrated HCl solution was used and at higher temperatures. Based on the EEI trend over time, a layer of silica gel layer forms around the sample, hindering further iron extraction. A maximum EEI of 93.79% was observed.

Structural Properties of Porous Silicon Carbide Bonded with Bentonite, Prepared by a Gas-Emitting Chemical Reaction Method

Direct foaming and bonding techniques were used to fabricate porous silicon carbide ceramics. Silicon carbide is characterized by a high melting temperature; it is always referred to as being bonded with low melting point materials such as bentonite. The technique of generating gases from the reaction of hydrochloric acid HCl with aluminum was used in silicon carbide-bentonite suspension, and by means of which high porosity bodies were prepared by adding different bentonite (10,15,20 and 25 wt.%). After molding them, it is dried and fired at 1100°C. The results of the X-ray diffraction analysis was founded that the main phases appearing after the firing process are α and β–SiC with quartz and mullite, where a part of (β–SiC) is transformed to (α-SiC) and transformation a part of Quartz to Tridymite, which means an increase in the stability of the crystalline phases. The porosity of specimens was decreased with bentonite increases after the firing process, and the values ranged between 62.3% and 72.3%. The compressive strength was increased with bentonite additions increases in the range from 4.35 MPa to 5.08 MPa. From the above results, it is clear that this type of porous (SiC-bentonite) composites can be used in fluid filtration with high efficiency, especially at high temperatures.

Understanding the Dechlorination of Chlorinated Hydrocarbons in the Pyrolysis of Mixed Plastics

The dechlorination of chlorine containing hydrocarbons in pyrolysis vapor is poorly understood. In order to shed new light on the dechlorination mechanism, a model mixture composed of iso-octane doped with 2-chlorobutane, 2-chloroethylbenzene, and chlorobenzene was used to study the dechlorination of chlorinated hydrocarbons by alkali adsorption. These three chlorinated hydrocarbons were selected as they can be typically produced from the pyrolysis of mixed plastic waste containing polyvinyl chloride (PVC). The mixture is pumped continuously through a Na₂CO₃ or CaCO₃/alumina bed, and GC-MS is used to identify the dechlorination products and to follow the dechlorination reactions. When chlorine is bonded to an aliphatic carbon with an adjacent aliphatic hydrogen, the chlorinated compound first undergoes a dehydrochlorination reaction to form HCl and olefins, and subsequently the HCl is reacted with the alkali in the absorbents. In our experiments, 2-chlorobutane is converted to 2-butene, and 2-chloroethylbenzene is converted to styrene. The formation of HCl and subsequent reaction with alkali components in the absorbent is verified by IR spectroscopy and XRD. In the presence of an alkali, the aliphatic chlorinated hydrocarbons underwent dechlorination at a temperature of 180 °C. The removal of chlorine from aromatic chlorinated compounds operates in a different mechanism, in which the C–Cl bond scission is promoted significantly by the presence of an alumina and hydrocarbon medium. It was found that chlorobenzene undergoes dechlorination forming phenol and benzene.

A Comparative Experimental Study of Alternative Iron Sulfide Scale Dissolvers in the Presence of Oilfield Conditions and Evaluation of New Synergists to Aminopolycarboxylic Acids

SummaryIssues such as high corrosion rate, hydrogen sulfide (or H2S) generation, and scale reprecipitation have required the use of alternative dissolvers such as tetrakis(hydroxymethyl)phosphonium sulfate (THPS)–ammonium chloride (or NH4Cl) blend and chelating agents to dissolve iron sulfide (or FeS) scales. However, there are many aspects of these dissolvers that need investigation. This paper provides a guideline to select the best dissolver under various oilfield conditions by an extensive laboratory study. Furthermore, the iron sulfide scale removal is enhanced by the use of new synergists to the chelating agents.The application of THPS and diethylenetriaminepentaacetic acid (DTPA) in well tubulars or pipelines requires laboratory testing to determine the optimal conditions such as dissolver concentration, treatment time, and dissolver/scale (D/S) ratio (cm3/g) at 150°F. This evaluation considers oil-wet scales, mixed scales, presence of additives, and presence of salts during the treatment. Synergists such as potassium chloride (or KCl), potassium iodide (or KI), potassium formate (or HCOOK), sodium fluoride (or NaF), and potassium citrate (or K-Citrate) were added to ethylenediaminetetraacetic acid (EDTA), DTPA, and hydroxyethylethylenediaminetriacetic acid (HEDTA), and the scale solubility was evaluated at 150 and 300°F. Inductively coupled plasma–optical emission spectrometer analysis of the supernatant solution at various intervals of time up to 48 hours revealed the kinetics of the dissolution process. H2S generated from the scale dissolution process was measured using Draeger tubes. Corrosion tests helped in measuring the damage to the tubulars as a result of the dissolver’s contact with N-80 coupons.Solubility tests indicated the dissolver’s scale removal capacity at different concentrations. The work also accounted for the consumption of the dissolver for the scale removal. The optimal blend was chosen considering both the dissolution capacity and the dissolver consumption. For THPS–ammonium chloride blend, 0.75 mol/L THPS (30 wt%) and 2 mol/L NH4Cl (10 wt%) proved to be the optimum dissolver concentration at 150°F. Similarly, for DTPA, 0.4 mol/L K2-DTPA was evaluated to be the most effective dissolver concentration. The THPS–ammonium chloride blend was found to dissolve the iron sulfide slowly compared with K2-DTPA and 15% hydrochloric acid (HCl). The presence of crude oil on the scale hindered its solubility with K2-DTPA by 8%. The presence of calcium carbonate influenced higher selectivity of chelating the calcium ions by K2-DTPA. However, the overall fraction of scale removal was not affected. Adding corrosion inhibitors (CIs) did not affect the scale solubility significantly and also helped in maintaining an acceptable corrosion rate of N-80 coupons below 0.05 lb/ft2 at 150°F. The reaction of HCl and the iron sulfide scale generated 1,800 ppm of H2S in comparison with 0- and 10-ppm by THPS–ammonium chloride blend and K2-DTPA, respectively. Adding potassium iodide and potassium citrate to EDTA helped in improving the scale solubility at 150°F. Sodium fluoride improved the scale dissolution by EDTA and DTPA at 300°F.This paper addresses oilfield-like conditions on scale solubility by evaluating the role of mixed scale, scale mass, presence of hydrocarbons on the scale, and presence of monovalent/divalent ions in dissolver solution. A detailed and direct comparison of HCl, THPS–ammonium chloride blend, and DTPA in dissolving iron sulfide at various conditions enables easier selection of the dissolver for a field treatment. New synergists for iron sulfide scale dissolution are introduced in this paper. This work can help oilfield companies understand the nuances of applying different alternative iron sulfide dissolvers.

Effect of microsolvation on the mode specificity of the OH˙(H2O) + HCl reaction.

The present study investigates the mode specificity in the microsolvated OH˙(H2O) + HCl reaction using on-the-fly direct dynamics simulation. To the best of our knowledge, this is the first study which aims to gain insights into the effect of microsolvation on the mode selectivity. Our investigation reveals that, similar to the gas phase OH˙ + HCl reaction, the microsolvated reaction is also predominantly affected by the vibrational excitation of the HCl mode, whereas the OH vibrational mode behaves as a spectator. Interestingly, in contrast to the behavior of the bare reaction, the integral cross section at the ground state of the microsolvated reaction decreases with an increase in translational energy. However, for the vibrational excited states, the reactivity of the microsolvated reaction is found to be higher than that of the bare reaction within the selected range of translational energies.

Mechanistic insights into the α-branched amine formation with pivalic acid assisted C-H bond activation catalysed by Cp*Rh complexes.

Density functional theory computations revealed a pivalic acid assisted C-H bond activation mechanism for rhodium catalyzed formation of α-branched amines with C-C and C-N bond couplings. The reaction energies of the [Cp*RhCl2]2 dimer and silver cations indicate that the Cp*RhCl+ cation is the active catalyst. The essential role of pivalic acid is a co-catalyst for the activation of the ortho-C(sp2)-H bond in phenyl(pyrrolidin-1-yl)methanone, while the reaction of NaHCO3 and HCl reduces the overall barrier of the catalytic cycle. In the presence of both pivalic acid and NaHCO3 in the reaction, the C(sp2)-H bond is activated through a concerted metallation deprotonation process, and the C-C bond coupling is the rate-determining step with a total free energy barrier of 23.9 kcal mol-1. Without pivalic acid and NaHCO3, the C(sp2)-H bond can only be activated through a σ-bond metathesis process and the free energy barrier increases to 32.2 kcal mol-1. We also investigated the mechanisms of a side reaction for β-branched amine formation and the reaction without styrene and found that their free energy barriers are 33.4 and 30.5 kcal mol-1, respectively.

The Effect of Anion Bridging on Heterogeneous Charge Transfer for V2+/V3+

Summary Vanadium redox flow batteries suffer from inefficiencies partly due to the kinetics of the V2+/V3+ reaction, for which lack of mechanistic understanding hinders electrolyte and electrocatalyst design to improve reaction rates. Here, we provide insights into the V2+/V3+ reaction in HClO4, H2SO4, HCl, HBr, and HI. We identify the V2+ and V3+ structures in these electrolytes using extended X-ray absorption fine structure, UV-vis, and density functional theory; this includes the hydrated structures of V2+ and V3+ in water (i.e., without anion complexation). We show that V2+/V3+ kinetics correlate with the energy of vanadium intermediate bound to carbon through a bridging anion (∗[bridge−V3+]). The anion-induced kinetic enhancement is from a decreased activation energy because of changing ∗[bridge−V3+] energy. The ∗[bridge−V3+] energy increases in the order of anion polarizability (OH−