Search

Herein we report binary acid Sc(OTf)3/TfOH-catalyzed alkenylation of arenes with alkynes. In this system, the high-energy vinyl carbocations with activated and weakly coordinating trifluoromethanesulfonate anions by Lewis acid Sc(III) can undergo facile Friedel-Crafts reactions with arenes to give the desired adducts in up to 90% yield and with high Z-selectivity.

Mesoporous SBA-15 has been synthesised using a binary acid H2SO4 as media. The effects of H2SO4 concentration and synthesis temperature on the morphologies and mesostructures of the obtained mesopo...

Herein, we disclosed an efficient protocol for the construction of chiral 3-allyl-3-hydroxyoxindoles via the enantioselective allylation reaction of isatins and allylboronates catalyzed by a simple binary acid Bi(OAc)3/CPA system under mild conditions. The synthetic utility of this strategy has been demonstrated through the formal synthesis of ent-CPC-1.

In this study, the inhibition effect of Tamarix Boveana (TB) extract on Cu corrosion in 1 mol L–1 (HNO3 + H3PO4) mixture was studied. Electrochemical techniques such as (potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM)) and non-electrochemical technique such as mass loss were used. Results showed that TB extract has good inhibition efficiency (IE), follows Langmuir adsorption isotherm and all of the methods are in good agreement. The IE increased by increasing the concentration of the extract and decreased by increasing the temperature so, the extract adsorbed on Cu surface physically. The IE depends on the concentration of the extract and reaches 73.5% at 300 ppm of the extract. PP results revealed that the (TB) extract doings as mixed type one. Surface analysis revealed that the extract components are adsorbed on Cu surface forming a film.

The increasing need for sustainable processes stimulates the production and recovery of renewable organic acids. The purification of these acids is often difficult because of similar acid volatilities but can be improved through extractive distillation. Generic insights into solvent effects on the separation efficiency for close-boiling acids are however lacking. This study provides insights into the effect of acidity, the acidity difference between the acids, the hydrogen-bonding strength of the solvent, and the solvent-to-feed ratio on organic acid separation efficiency. For an acetic acid-formic acid (AA-FA) mixture, the addition of high-boiling organic acids increases the relative volatility of FA over AA significantly. The addition of a Lewis base reverses the relative volatility, which depends on the applied solvent-to-feed ratio and the Lewis base BF3 affinity. For several binary acid mixtures (such as AA-FA and monochloroacetic acid-dichloroacetic acid), where the acids have a relatively big difference in acidity (ΔpKa ≥ 1), the separation selectivity appears practically independent of the acid strength of the individual acids and increases with increasing BF3 affinity of the Lewis base. For acid mixtures with a lower ΔpKa, a lower separation selectivity is obtained, as observed for separation of the pivalic acid-butyric acid and valeric acid-2-methyl butyric acid mixtures. When one of the acids in the mixture contains a secondary ketone group (i.e., levulinic acid in a levulinic acid-octanoic acid mixture), the strongest acid based on pKa is not necessarily attracted most by the added Lewis base. This, at first sight, unexpected behavior is most likely the result of complex intra- and intermolecular interactions and is quantitatively in line with COSMO-RS-based selectivity predictions.

Monodisperse SBA-15 rods with tunable size, synthesized by a facile and low-cost route using different types of acids (HCl (monobasic acid), H2SO4 (binary acid) and H3PO4 (ternary acid)) as media and inexpensive powder quartz as silica source without any additives, was developed as an absorbent to extract uranium from radioactive waste water. The effect of the type of acid on the structure and morphology of the obtained mesoporous SBA-15 was investigated. SBA-15 rods with varying lengths (1082–1354 nm) and diameters (279–361 nm) were tailored by simply using different types of acids. The number of H in acid molecular was identified to be the key factor affecting the structure and morphology of the SBA-15 rods. It was found that the length and diameter of these SBA-15 rods increased with increase of the number of H in acid molecular. Furthermore, the adsorption behavior of uranium on these SBA-15 rods was investigated and the results showed that all these SBA-15 rods demonstrated rapid (30 min to reach equilibrium) and high capacity (235 mg g−1) for adsorption of uranium. This work demonstrated that these SBA-15 rods prepared with different types of acids from powder quartz exhibited improved performance for the extraction of uranium.

The behavior of Cu in 1 M mixture of nitric and phosphoric acids containing different concentrations of moringa oleifera leaves (MOL) extract has been studied by weight loss (WL) and electrochemical techniques [potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM)]. The maximum inhibition efficiency was found to be 89% at concentration 0.300 mol L-1 of the extract at 298K after 3 hours immersion period. The inhibition efficiency (IE) increased with increasing the extract concentration while decreased with increasing the temperature indicates that the extract is physically adsorbed on Cu surface. The adsorption of the extract follows Langmuir adsorption isotherm. Some thermodynamic parameters of activation and adsorption processes were also determined and discussed. Surface analysis was also studied.

Since the pioneering independent reports of Akiyama and Terada, the use of chiral phosphoric acids (CPAs) and derivatives as a versatile tool for asymmetric synthesis with good reactivity, regioselectivity, diastereoselectivity and enantioselectivity has emerged, forming an important part of the implementation of asymmetric counteranion-directed catalysis reported to date. In these achievements, the combination of metals with CPAs has enabled various catalytic modes beyond the scope of typical acid catalysis, such as relay catalysis, ion-pairing catalysis, and binary acid catalysis. The first-row transition metals (Sc–Zn) are considered to be sustainable transition metals and have received a great deal of attention. These naturally abundant metals display excellent Lewis acidity and function as powerful redox catalysts in synthesis involving both one and two-electron transfers. Hence, in this chapter, we summarize recent advances in the development of asymmetric reactions using a combination of first-row transition metals and CPAs. Furthermore, we provide a detailed discussion of the mechanisms involved in order to understand the interaction of the metal/phosphate and the origins of the asymmetric control of the transformations.

An unprecedented binary acid accelerated oxidative radical annulation of sulfonyl hydrazones with simple olefins is described. Notably, this method provides a novel oxidative radical cycloaddition for the construction of six-member heterocycles. It offers a rapid and efficient approach to tetrahydropyridazines which are key structural motifs in pharmaceutically active compounds.

An efficient binary acid catalyzed asymmetric intramolecular tandem 1,5-hydride transfer/ring-closure reaction was achieved. The process is catalyzed by the combination of a chiral spirocyclic phospho­ric acid and magnesium chloride to afford structurally diverse spirooxindole tetrahydroquinolines in good yields with high diastereo- and enantioselectivities.

The exchange of the metal ion from In(III) to Sc(III) in a binary acid catalyst leads to a switch in the diastereoselectivity of [4 + 2] cycloadditions.

On the basis of 1,4-bis(2-methyl-imidazol-1-yl)butane (bib), four new coordination polymers (CPs), namely, {[Zn(bib)(male)] 2 ·2H 2 O} n (1) , {[Zn(bib)(suc)]·H 2 O} n (2) , {[Zn(bib)(fum)]·CH 3 OH} n (3) , {[Zn(bib)(bpdc)]·2H 2 O} n (4) (H 2 mal = maleic acid, H 2 suc = succinic acid, H 2 fum = fumaric acid, bpdc 2 - − = 2,2’2′-bipyridine- 3,3’3′-dicarboxylate) have been synthesized by the reaction of zinc(II) salts and bib with four different aliphatic/aromatic binary acids under the same conditions, respectively. These coordination polymers are structurally characterized by elemental analysis, IR, single-crystal X-ray crystallography and TG analysis. All of them host a same meso -helical chain constructed by metal centers and bib ligands. 1 and 2 feature similar 2-D wave-like topology containing a meso -helical chain; 3 is a 3-D diamond-like structure, comprising two different meso -helical chains, and shows 4-fold interpenetrated framework with {6^6} topology; 4 is a 3-D diamond-like structure, containing a meso -helical chain, and displays 3-fold interpenetrated net with {6^6} topology. In addition, the phase purities of bulk samples were further identified by X-ray powder diffraction analysis. Solid state luminescent spectra have been investigated at room temperature, and the luminescent lifetime of 3 was monitored at room temperature.

Certain processes, such as proton transfer or dissociation, can introduce inconsistencies into computational techniques based on the many-body expansion if the identities of the fragments that define the expansion change. This report uses simple binary acid/base clusters to illustrate this potential problem and to quantify the effects of these inconsistencies on the total and relative electronic energies of the clusters. The 2-body:Many-body CCSD(T):MP2 approach developed in our lab typically deviates from CCSD(T) reference values by only a few hundredths of a kcal mol −1 for clusters in which monomer-based fragment definitions are entirely consistent. These deviations generally grow to at least several tenths of a kcal mol −1 for clusters where inconsistencies are introduced by such simple fragment definitions. In fact, the magnitude of the discrepancies can actually exceed 1 kcal mol −1 (or 25%) for the relative electronic energies.

An unprecedented binary acid accelerated oxidative radical annulation of sulfonyl hydrazones with simple olefins is described. Notably, this method provides a novel oxidative radical cycloaddition for the construction of six-member heterocycles. It offers a rapid and efficient approach to tetrahydropyridazines which are key structural motifs in pharmaceutically active compounds.

An efficient binary acid catalyzed asymmetric intramolecular tandem 1,5-hydride transfer/ring-closure reaction was achieved. The process is catalyzed by the combination of a chiral spirocyclic phospho­ric acid and magnesium chloride to afford structurally diverse spirooxindole tetrahydroquinolines in good yields with high diastereo- and enantioselectivities.

We describe herein a viable binary acid strategy for the catalytic Nazarov reaction of aryl vinyl ketones. Simply combining a Lewis acid and a Brønsted acid led to a dramatic enhancement of the catalytic activity in the Nazarov reaction of aryl vinyl β-ketoesters. The obtained optimal binary acid catalyst In(OTf)(3)/diphenyl phosphoric acid (DPP) can be applied to a range of aryl vinyl ketones with good activity. A trend of reactivity has also been summarized on the basis of mapping of the substituents.

A mechanistic study of the tert-aminocyclization reaction was performed by using DFT calculations and labeling experiments. The results showed that the reaction proceeded through a rate-limiting-, stereospecific-, and suprafacial 1,5-H-transfer pathway, followed by a barrier-less C-C bond formation. The mode of stereocontrol for facial selection could be ruled out owing to the high activation energy of C-N bond rotation. The intrinsic feature of this Lewis acid activation was found to be the activation of the LUMO, as well as an intermediate-stabilization effect. The catalytically active species was believed to be a 1:1 complex of phosphoric acid and MgCl(2), which was stabilized by a H⋅⋅⋅Cl hydrogen bond. The chiral catalytic complex selectively recognizes and activates one of the two helical conformations of substrate A, required for 1,5-suprafacial H-transfer, which dictates the stereoselectivity of the forming products.

Swapping the anions of an indium Lewis acid leads to a remarkable regioselectivity switch between asymmetric 1,2- and 1,4-addition reactions of N-protected indoles (II) and β,γ-unsaturated α-keto esters (III).

A new binary acid system featuring an air stable organometallic precursor, titanocene dichloride and a simple Bronsted acid–base compound, was developed. The new catalyst system allowed for mild an...

This work deals with the study of corrosion behaviour for zinc in (HNO3+ H2SO4) binary acid mixture containing ethanolamines. Corrosion rate increases with concentration of acid and temperature. At constant acid concentration, the inhibition efficiency of ethanolamines increases with the inhibitor concentration. Value of ΔGa increases and inhibition decreases with temperature. The mode of inhibition action appears to be chemisorption.

A series of novel cross-linkers, N-hydroxysuccinimide (NHS)-activated end-bit binary acid (NHS-C4, C5, C6, C8, C10, C14), were synthesised to modify gelatin films and the crosslinking effects were compared. Homogeneous films with the exception of the film crosslinked by NHS-C14 were observed and the thickness was measured using a scanning electron microscope. The section feature influenced by different film-treatment conditions was also recorded. The differential scanning calorimetry results indicated higher thermal stability. The water contact angles confirmed enhanced hydrophobicity. NHS-C6, which was used as a probe crosslinker, exhibited the best crosslinking effect that the content of the free -NH2 achieved was the lowest out of all the crosslinkers. The biodegradation results of gelatin films modified by NHS-C6 exhibited better degradation-resistance and excellent stability. In addition, the optimal experimental conditions were 45°C for 12 h when [NHS-C6]/[-NH2] = 2.5.

Pristine carbon nanotubes (CNTs) dissolve as polycarbocations in superacids through direct protonation. The solvating power of a superacid is determined by the stability of the conjugate base anion that competes with the CNTs for the dissociated proton. We have demonstrated that this equilibrium can be controlled in a predictable fashion, thus rendering the solvating power of a superacid system tunable. In this article, we show that the solvating power of chlorosulfonic acid can be changed in a desired fashion by forming binary mixtures in different proportions with a non-superacid such as methane sulfonic acid. Thus, the successive extraction of carbon nanotubes with binary acid mixtures of increasing solvating power leads to the differentiation of CNTs by their molecular geometry. We show that solvation by direct protonation is sensitive to the geometric strain at the carbon atom and, hence, to the nanotube diameter. In this respect, the direct protonation method is distinct from surfactant-based or electrical-field-based methods that distinguish metallic CNTs from semiconducting types mainly on the existence of finite density of states or not at the Fermi level. We have employed solid-state Raman spectroscopic analysis of the CNT radial breathing modes and UV-vis absorption spectroscopy and a systematic mapping method to support our conclusions. We believe the concept demonstrated in this paper holds the potential to be developed into a chemical tool kit useful in the scaleable separation of CNTs by their (n, m) types, thus paving the way for molecular carbon nanotechnology.

As an emerging method for the direct asymmetric functionalization of C(sp3)–H bonds, the asymmetric [1,5]-hydride transfer reactions have received considerable attention in recent years. The remarkable features of these reactions include their redox-neutral nature and facile access to versatile polycyclic scaffolds when coupled with the downstream cyclization process. Thanks to the continuous efforts in this field, an array of effective catalytic systems such as chiral organocatalysts, Lewis acids, and binary acid catalysts that are capable of promoting asymmetric [1,5]-hydride transfer reactions has been identified. This chapter will focus on providing a concise description of the state-of-the-art of this exciting area.

The Raman spectroscopy technique has been employed to probe, as a function of temperature, the ionic and molecular speciation within the aqueous phase for systems of potential relevance to stratospheric chemistry. The systems studied, over the temperature range 200−300 K, were (i) binary HNO3:H2O and H2SO4:H2O mixtures and (ii) ternary HNO3:H2SO4:H2O (NSW) mixtures. The contributions of the concentration coefficient, Qm, to the equilibrium dissociation constants were assessed from the spectroscopic data. It was observed that speciation within the binary acid systems shifts toward the ionized form as temperature and concentration decrease because of increasing proton stabilization. The ternary NSW acid displays some similar properties to the binary counterparts, though a dominance of SO42-aq over NO3-aq ions in the competition for protons is observed. This effect leads to the HSO4- ion becoming the principal associated acid form and its presence is found to determine the behavior of the NSW systems at all ...

A binary acid system has been developed that features an air-stable organometallic precursor, titanocene dichloride, and simple organic cooperative Bronsted acids, which allowed for mild and highly efficient Mannich reactions of both aryl and alkyl ketones with excellent yields and satisfactory diastereoselectivity. Mechanistic studies, including (1) H NMR titration, X-ray structure analyses as well as isolation of catalytically active species, elucidated the dramatic synergistic effects of this new binary acid system.

Thermal reactions of the binary alkali salts of poly(carboxylic acid)–brominated carboxylic acid such as sodium or potassium poly(4-vinylbenzoate)-2-bromopropanoate [Na or K (PVBA-2-BPA)] in bulk were investigated. A methanol solution of binary acids was prepared by fixing the molar ratio of the repeating unit of polymeric acid to the fraction of brominated carboxylic acid. The binary salts were prepared by the neutralization of the binary acid solution. The product of the thermal reaction followed by esterification was identified as a graft copolymer containing PVBA in the main chain and polylactic acid in the side chain. The reaction of 1/15 K (PVBA-2-BPA) at 120 °C for 2 h yielded the highest percentage of grafting (300%). The grafting proceeded gradually for the initial 2 h and then somewhat. Reactivity of the K salt was higher than that of the corresponding Na salt. The thermal reaction of 1/10 K [polymethacrylate-2-BPA (PMA-2-BPA)] at 120 °C for 2 h also yielded a graft copolymer, and the percentage of grafting was 300%. However, reaction temperatures higher than 120 °C caused homopolycondensation of K 2-BPA prior to grafting, and homopolycondensation occurred prior to grafting in the reaction with Na (PMA-2-BPA). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1877–1885, 2001

Equilibrium isotherms have been determined for the adsorption of two single-component and one binary acid dye solutions on carbon. The ideal adsorbed solute theory (IAST) has been used to predict isotherm data for the binary system using the single-component dye sorption data alone. A detailed analysis has been carried out to investigate the effect of different error criteria for determining single-component isotherm parameters and their influence on the results of IAS model simulations using the Langmuir and Freundlich isotherm equations. It was found that the “best-fit” single-component isotherm based on the minimum error criteria did not result in the “best-fit” IAS model predictions. Furthermore, the IAS model producing the closest fit to the binary experimental data did not use the same isotherm model as the single-component data for one dye. Reasons for this apparently anomalous behaviour have been discussed and the most likely cause appears to be dye–dye interactions in the binary system.

The exchange of the metal ion from In(III) to Sc(III) in a binary acid catalyst leads to a switch in the diastereoselectivity of [4 + 2] cycloadditions.

It is demonstrated that the combination of In(OTf)3/benzoic acid efficiently catalyzes the coupling of alkynes and acetales to afford indanones in excellent yield and diastereoselectivity.

A single piezoelectric quartz crystal coated with one kind of crown ether was applied to the simultaneous determination of binary acid and amine vapor mixtures. From the adsorption and desorption curves of analytes, which were somewhat different in shape, frequency shifts from ten time windows were taken as inputs for artificial neural networks (ANN). Prediction results were satisfactory for ANN in both sample sets. The average relative errors, for formic acid and acrylic acid were 5%, for n-butylamine and aniline, they were 3% with ANN respectively. The effects of number of neurons in the hidden layer of ANN on the performance of the network are also discussed.

A facile tandem [2 + 2] cycloaddition and Nazarov reaction has been developed. The combination of In(OTf)3 and benzoic acid was found to synergistically promote the coupling of alkynes and acetals to form 2,3-disubstituted indanones in excellent yield and diastereoselectivity.

Nazarov reaction of aryl vinyl β-ketoesters is optimally catalyzed by a binary acid catalyst consisting of In(OTf)3 and diphenyl phosphoric acid (DPP).

Recently, chiral Bronsted acids as dual ligand and acid catalysts in the context of metal catalysis have been developed. Such binary catalytic systems synergistically integrate chiral Bronsted acids and metal catalysts as a result of their weakly coordinating behaviors. The resulting binary acid catalysts have enabled effective reactions of a range of olefins/aromatics, beyond the scope of typical acid catalysis. Our endeavors in developing asymmetric binary acid catalysis are summarized in this feature article.

Selective H transfer by ABC: A new asymmetric binary acid catalyst was developed to promote 1,5-H transfer specifically and stereoselectively in tert-aminocyclization reactions with excellent activity, high enantioselectivity, and broad substrate scope. The H atom (in red) was proven to transfer through a stereospecific suprafacial pathway (see scheme).

Recently, chiral Bronsted acids as dual ligand and acid catalysts in the context of metal catalysis have been developed. Such binary catalytic systems synergistically integrate chiral Bronsted acids and metal catalysts as a result of their weakly coordinating behaviors. The resulting binary acid catalysts have enabled effective reactions of a range of olefins/aromatics, beyond the scope of typical acid catalysis. Our endeavors in developing asymmetric binary acid catalysis are summarized in this feature article.

Selective H transfer by ABC: A new asymmetric binary acid catalyst was developed to promote 1,5-H transfer specifically and stereoselectively in tert-aminocyclization reactions with excellent activity, high enantioselectivity, and broad substrate scope. The H atom (in red) was proven to transfer through a stereospecific suprafacial pathway (see scheme).

Swapping the anions of an indium Lewis acid leads to a remarkable regioselectivity switch between asymmetric 1,2- and 1,4-addition reactions of N-protected indoles (II) and β,γ-unsaturated α-keto esters (III).

Remote F effect: Unprecedented hetero-Diels-Alder reactions of mono- and bis-substituted cyclopentadienes have been realized by an asymmetric binary-acid catalyst that synergistically combines a chiral phosphoric acid 1 h/InBr(3) with good periselectivity, high regioselectivity, and excellent stereoselectivity. Substituent mapping of the chiral phosphoric acid indicates a dramatic remote ortho-fluoro effect on the stereocontrol.

A unique binary chiral phosphoric acid 1a/MgF2 catalyst that enables effective catalysis of asymmetric Friedel−Crafts reactions of phenols with up to 82% yield and >99% ee is presented. A dramatic synergistic effect has been observed in the combinations of two types of acids, wherein a highly active binary-acid catalyst can be generated from two individually inert acids.

Photodegradation and mineralization of single and binary Acid Orange 7 (AO7) and Reactive Red 2 (RR2) under UV irradiation in TiO(2) suspensions was examined. Experiments were conducted as a function of initial pH, TiO(2) dose, and initial dye concentration. First-order derivative spectrophotometric method was used to simultaneously analyze AO7 and RR2 in binary solutions. The Langmuir-Hinshelwood kinetic model was applied to evaluate and compare the apparent rate constants for the photodegradation of both dyes in single and binary solutions. It was shown that photodegradation of both dyes in binary solution was slower than those in single solution under comparable conditions. Moreover, the difference between the apparent rate constants of RR2 and AO7 became smaller in contrast to the cases of single solutions. After 20-min UV irradiation with 0.5 g/L TiO(2), complete removal of single 0.086 mM AO7 and 0.086 mM RR2 at pH 6.8 was obtained, but only 60% and 45% of binary 0.086 mM AO7 and 0.086 mM RR2 was removed, respectively.

A unique binary chiral phosphoric acid 1a/MgF2 catalyst that enables effective catalysis of asymmetric Friedel−Crafts reactions of phenols with up to 82% yield and >99% ee is presented. A dramatic synergistic effect has been observed in the combinations of two types of acids, wherein a highly active binary-acid catalyst can be generated from two individually inert acids.

The structures of four isomeric compounds, all C7H4ClNO4.C9H7N, of quinoline with chloro- and nitro-substituted benzoic acid, namely, 2-chloro-5-nitrobenzoic acid-quinoline (1/1), (I), 3-chloro-2-nitrobenzoic acid-quinoline (1/1), (II), 4-chloro-2-nitrobenzoic acid-quinoline (1/1), (III), and 5-chloro-2-nitrobenzoic acid-quinoline (1/1), (IV), have been determined at 185 K. In each compound, a short hydrogen bond is observed between the pyridine N atom and a carboxyl O atom. The N...O distances are 2.6476 (13), 2.5610 (13), 2.5569 (12) and 2.5429 (12) A for (I), (II), (III) and (IV), respectively. Although in (I) the H atom in the hydrogen bond is located at the O site, in (II), (III) and (IV) the H atom is disordered in the hydrogen bond over two positions with (N site):(O site) occupancies of 0.39 (3):0.61 (3), 0.47 (3):0.53 (3) and 0.65 (3):0.35 (3), respectively.

Corrosion of Zinc metal in (HNO 3 + HCl) binary acid mixture and inhibition efficiency of aniline has been studied by weight loss method and polarization technique. Corrosion rate increases with the concentration of acid mixture and the temperature. Inhibition efficiency (I.E.) of aniline increases with the concentration of inhibitor while decreases with the increase in concentration of acid. As temperature increases corrosion rate increases while percentage of I.E. decreases. A plot of log (θ/1-θ) versus log C results in a straight line suggest that the inhibitor cover both the anodic and cathodic regions through general adsorption following Longmuir isotherm. Galvenostatic polarization curves show polarization of both anodes as well as cathodes.