Exchange reactions of alkyl residues in the presence of orthophosphoric and benzenephosphonic monoesters

Experimental data obtained from the study of the behaviour of monoalkyl phosphates ROP(O)(OH)O^? or monoalkyl phosphonates C₆H₅P(O)(OR)O^? in aquo-alcoholic (H₂O + R′OH) solutions suggest: (1) in the case of monoalkyl phosphonates the exchange of R and R′ must proceed by a direct alcoholysis; (2) in the case of monoalkyl phosphates, where the scission of the ester at about pH 4,5 proceeds via the intermediate formation of metaphosphate ion PO₃^?, R′OPO₃H^? can also be formed by the addition of R′OH to PO₃^? (competitive to the addition of water) besides direct alcoholysis of ROPO₃H^?.     

Molecular interactions in aqueous solutions of polyborates at different acidity based on the Raman spectroscopy data at 25°C

Investigation of aqueous solutions of polyborates LiB(OH)₄, Li₂B₄O₅(OH)₄, and LiB₅O₆(OH)₄ at different acidity has been performed by Raman spectroscopy at 25°C. The geometries and Raman vibrational frequencies of H₃BO₃ in aqueous phase were calculated at different basis sets, and verified the veracity. The calculated characteristic Raman shifts of B(OH)₃, B(OH)₄ ^?, B₃O₃(OH)₄ ^?, B₃O₃(OH)₅ ^2?, B₄O₅(OH)₄ ^2?, and B₅O₆(OH)₄ ^? were assigned to 880.0, 735.33, 599.06, 740.16, 551.67, and 521.04 cm^?1, respectively. Assignments of the bands were tentatively ascribed by comparing the calculated Raman spectrum. The chemical species distribution and the relevant molecular interaction mechanisms in the polyborates solutions were suggested.     

About the OH yield in the radiolysis of an aqueous/H2O2 system. Its optimisation for water treatment

Unless the radiolytic reducing species are neutralised or converted into oxidising species, an EB remediation system cannot be considered a true Advanced Oxidation Processes (AOP). A water/H₂O₂ system irradiated by UVC mercury lamps constitutes a widely used OH production method. Employing H₂O₂ in radiolysis as well, an enhancement of the oxidative efficiency of an EB treatment can be obtained. Pulse radiolysis measurements of an aerated aqueous/H₂O₂/KSCN system have been systematically undertaken to assess the optimal H₂O₂ concentration. By linearly fitting a competition kinetics relationship, it is found that the scavengeable extra-yield of OH is ΔG(OH)=0.24 μmol J^?1 (R=0,9958), while the maximum experimental yield is measured G(OH)_max=(0.52±0.02) μmol J^?1 when [H₂O₂]=5–10 mM. Exceeding these concentrations the OH yield drops off.     

Alkoxycarbonyl- and Carboxylate-Group Migrations in the Benzilic Acid Rearrangement of Ethyl Cyclopropane-2, 3-dioxopropionate

In alkaline medium C₃H₅? CO? C (OH)₂? COOEt ( 1b ) is transformed into C₃H₅? C (OH)(COOH)₂ ( 2a ). Labelling experiments show that the cyclopropyl group is not shifted, but only ROOC and/or ^?O₂C groups. GC./MS. and NMR. analysis after incomplete reaction show that both ROOC- and ^?O₂C-groups Migrate; at higher pH (ca. 14) the ester group rearrangement seems to be more important than at pH ca.9-10.     

Host-guest interactions based supramolecular complexes self-assemblies for amplified chemodynamic therapy with H2O2 elevation and GSH consumption properties

Although endogenous H₂O₂ is overexpressed in tumor tissue, the amount of endogenous H₂O₂ is still insufficient for chemodynamic therapy (CDT). In addition, the abundant cellular glutathione (GSH) could also consume ^?OH for reduced CDT. Thus, the elevation of H₂O₂ and the consumption of GSH in tumor tissue are essential for the increased ^?OH yield and amplified CDT efficacy. In this paper, host-guest interactions based supramolecular complexes self-assemblies (SCSAs) were fabricated by incorporating cinnamaldehyde (CA) and PEG-modified cyclodextrin host units (mPEG-CD-CA) with ferrocene-(phenylboronic acid pinacol ester) conjugates (Fc-BE) on the basis of CD-induced host-guest interactions. After being internalized by cancer cells, CA can be released from SCSAs through the pH-responsive acetal linkage, elevating the H₂O₂ level by activating NADPH oxidase. Then, Fc can catalyze the H₂O₂ to higher cytotoxic hydroxyl radicals (^?OH). Moreover, quinone methide (QM) can be produced through H₂O₂-induced aryl boronic ester rearrangement and further consume the antioxidant GSH. In vitro and in vivo experiments demonstrate that SCSAs can be provided as potential amplified CDT nanoagents.     

Characterization and spectroscopic study of new complexes of Cd(II), Hg(II) and Pb(II) with the sodium salt of morin-5′-sulfonic acid

Solid compounds of Cd(II), Hg(II) and Pb(II) with the sodium salt of morin-5′-sulfonic acid (NaMSA) were obtained. The molecular formula of the complexes are: Cd(C₁₅H₈O₁₀SNa)₂?·?6H₂O, CdOH(C₁₅H₈O₁₀SNa)?·?4H₂O, Hg(C₁₅H₈O₁₀S)?·?4H₂O and Pb(C₁₅H₈O₁₀S)?·?3H₂O. Some of their physicochemical properties such as UV-Vis, infrared, ¹³C NMR and mass spectra, thermogravimetric analysis, and solubility were studied. On the basis of spectroscopic data NaMSA was bound to Cd²⁺ via 4C=O and 3C?–?oxygen and the Hg²⁺ and Pb²⁺ ions by 5C–OH, 4C=O and 3C–OH.     

Determination of Four Active Oxygen Species Such as H2O2, •OH, •O2 −, and 1O2 by Luminol and CLA-Chemiluminescence Methods and Evaluation of Antioxidative Effects of Hydroxybenzoic Acids

Abstract

Simple and rapid chemiluminescence (CL) assays for H₂O₂, ?OH, ?O₂ ^? and ¹O₂ using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H₂O₂ (25-120 μM), ?OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H₂O₂, ?O₂ ^? generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10^?3 units xanthine oxidase (XO) and ¹O₂ generated from NaOCl (3-12 mM) in the presence of 97.6 μM H₂O₂ were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H₂O₂, ?OH, ?O₂ ^? and ¹O₂ of other dihydroxybenzoic acids were also evaluated.     

Structure of Aqueous Lithium Tetraborate Solution

The structure of aqueous lithium tetraborate solutions was investigated by species distribution calculation and synchrotron X-ray scattering. It shows that the dominant species in supersaturated solution at 298.15 K is B₄O₅(OH) ₄ ^2? and the minor species are B₃O₃(OH) ₅ ^2? , B₃O₃(OH) ₄ ^? and B(OH)₃. The ‘intramolecular’ structural parameters of B₄O₅(OH) ₄ ^2? , such as bond length and coordination number, were gives out using density function theory calculation. X-ray scattering study shows that the distance Li–O(H₂O)_I of [Li(H₂O)₄]⁺ is about 0.1983 nm with the coordination number(CN) 4 in tetrahedral configuration. The B–O(H₂O) distance in hydrated anion B₄O₅(OH)₄(OH₂) ₈ ^2? is 0.3662 nm with the CN 12. The Li⁺–B distance is about 0.3364 nm with a coordination number ~1.0. The temperature effect on solution structure was also discussed.     

Über Reaktionen oxygenierter Kobalt(II)-Komplexe. IX. Oxydative Eigenschaften von Tetrakis(äthylendiamin)-μ-peroxo-μ-hydroxo-dikobalt(III)

Reactions of oxygenated cobalt(II) complexes. IX. Oxidative properties of tetrakis(ethylenediamine)-μ-peroxo-μ-hydroxo-dicobalt(III)

1 VIII s. [1].

[(en)₂Co(O₂, OH)Co(en)₂]³⁺ ( a ) reacts with I^? in acidic aqueous solution according to: Co^III(O₂, OH)Co^III + 21^? + 5H⁺ ? 2Co^III + 3H₂O + I₂. Using I^? in excess first order rate constants are obtained which, to a first approximation, are independent of [I^?]. Comparison with kinetic data of deoxygenation of [(en)₂Co(O₂, OH)Co(en)₂]³⁺ under analogous conditions suggests that both reactions have the same rate determining step. The singly bridged species [(en)₂(H₂O)CoO₂Co(H₂O) (en)₂]⁴⁺ is shown to be the reactive intermediate in the iodide oxidation (Schema 2).     

In situ synthesis of red fluorescent gold nanoclusters with enzyme-like activity for oxidative stress amplification in chemodynamic therapy

Chemodynamic therapy（CDT） has attracted tremendous interest in cancer therapy because it is independent of oxygen and photoirradiation.However,the therapeutic efficacy of CDT is restricted by insufficient H₂ O₂ levels in tumor cells.Herein,employing endogenous GSH as a template and cationic polymeric chitosan（CS） as crosslinker and stabilizer exhibiting easy cell uptake,red luminescent gold nanoclusters（denoted CS-GSH@AuNCs） were successfully synthesized in HeLa cells.The i...     

Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II,Their Reactivity toward Organic Substrates,and the Influence of N‐Methylimidazole Axial Ligation

High‐valent iron‐oxo species have been invoked as reactive intermediates in catalytic cycles of heme and nonheme enzymes. The studies presented herein are devoted to the formation of compound II model complexes, with the application of a water soluble (TMPS)Fe^III(OH) porphyrin ([meso‐tetrakis(2,4,6‐trimethyl‐3‐sulfonatophenyl)porphinato]iron(III) hydroxide) and hydrogen peroxide as oxidant, and their reactivity toward selected organic substrates. The kinetics of the reaction of H₂O₂ with (TMPS)Fe^III(OH) was studied as a function of temperature and pressure. The negative values of the activation entropy and activation volume for the formation of (TMPS)Fe^IV?O(OH) point to the overall associative nature of the process. A pH‐dependence study on the formation of (TMPS)Fe^IV?O(OH) revealed a very high reactivity of OOH^? toward (TMPS)Fe^III(OH) in comparison to H₂O₂. The influence of N‐methylimidazole (N‐MeIm) ligation on both the formation of iron(IV)‐oxo species and their oxidising properties in the reactions with 4‐methoxybenzyl alcohol or 4‐methoxybenzaldehyde, was investigated in detail. Combined experimental and theoretical studies revealed that among the studied complexes, (TMPS)Fe^III(H₂O)(N‐MeIm) is highly reactive toward H₂O₂ to form the iron(IV)‐oxo species, (TMPS)Fe^IV?O(N‐MeIm). The latter species can also be formed in the reaction of (TMPS)Fe^III(N‐MeIm)₂ with H₂O₂ or in the direct reaction of (TMPS)Fe^IV?O(OH) with N‐MeIm. Interestingly, the kinetic studies involving substrate oxidation by (TMPS)Fe^IV?O(OH) and (TMPS)Fe^IV?O(N‐MeIm) do not display a pronounced effect of the N‐MeIm axial ligand on the reactivity of the compound II mimic in comparison to the OH^? substituted analogue. Similarly, DFT computations revealed that the presence of an axial ligand (OH^? or N‐MeIm) in the trans position to the oxo group in the iron(IV)‐oxo species does not significantly affect the activation barriers calculated for C?H dehydrogenation of the selected organic substrates.     

A New Organic‐Inorganic Hybrid Copper Pentaborate with Free Boric Acid Group

The hydrothermal reaction of Cu(CH₃COO)₂·H₂O, H₃BO₃, ethylenediamine and H₂O in a molar ratio of 3:20:9:222 at 140°C for 5 d yields the deep blue crystals of a new copper polyborate [Cu(en)₂B(OH)₃]· [B₅O₅(OH)₇] (en?H₂NCH₂CH₂NH₂) in 70% yield. It crystallizes in monoclinic system, space group P2₁/c, with unit cell dimensions, a=1.2779(2) nm, b=1.0167(15) nm, c=1.5019(2) nm, β=90.30(2)°, Z=4. The crystal structure of this compound consists of [Cu(en)₂B(OH)₃]²⁺ cation and [B₅O₅(OH)₇]^2? anion, which are linked together through hydrogen bonding interactions and electrostatic forces, forming an interesting three‐dimensional framework. The [B₅O₅(OH)₇]^2? anion is constituted of [B₄O₅(OH)₄]^2? anion and discrete B(OH)₃ group which attaches to the side of [B₄O₅(OH)₄]^2? through intramolecular hydrogen bonds. Fundamental vibrational modes of this compound were identified and band assignments were made. The middle bands observed at 882 and 575 cm^?1 in Raman spectrum are the characteristic peak of B(OH)₃ group and [B₄O₅(OH)₄]^2? anion, respectively. Additionally the thermal behavior of title compound was recorded and its decomposition mechanism was discussed.     

Rate coefficient for the reaction OH + HO2 = H2O + O2 at 1 atmosphere pressure and 308 K

The rate coefficient for the reaction OH + HO₂ =H₂O + O₂ has been determined from measurements of the steady-state absorption of HO₂ at 210 nm, in low-frequency square-wave modulated photolysis of O₃ + H₂O mixtures. The value obtained was (9.9 ± 2.5) × 10^?11 cm³ molecule^?1 s^?1 at 308 K and 1 atm pressure.     

Kinetics of the borate anion catalyzed oxidation of diethyl sulfide with hydrogen peroxide in an <Emphasis Type="Italic">i</Emphasis>-PrOH–H<Subscript>2</Subscript>O medium

It was found that in a wide range of pH in the presence of boric acid the oxidation of diethyl sulfide (Et₂S) with hydrogen peroxide in an i-PrOH–H₂O medium occurs with the participation of H₂O₂, HOO^–, monoperoxo-(B(OH)₃OOH^–), and diperoxoborates (B(OH)₂(OOH)₂⁻). The stability constants of peroxoborates and the rate constants for the reactions of H₂O₂, HOO⁻, B(OH)₃(OOH)₂⁻, and B(OH)₂(OOH)₂⁻ with Et₂S under these conditions were determined.     

Effects of the Pulse Polarity on Helium Plasma Jets: Discharge Characteristics,Key Reactive Species,and Inactivation of Myeloma Cell

In this paper, we report the effects of the pulse polarity on the plasma jet’s discharge characteristics, particularly, on the production of the reactive oxygen and nitrogen species (RONS) and the inactivation efficiency of myeloma cells, for the purpose of identifying and elucidating the correlation between the dose of RONS and cell viability. Experimental results reveal that the positive plasma jet has a longer length than that for negative plasma jet with the equivalent pulse power. The positive pulse plasma jet would produce higher production of the excited reactive species (OH(A), N₂(C), N₂⁺(B), He(3s³S), O(3p⁵P)), the positive ions (N⁺, O⁺, N₂⁺, O₂⁺), and the aqueous species O₂^?, OH, and ONOO^?, while negative plasma jet would generate higher concentration of the negative ions (OH^?, O₂^?, NO₂^?, NO₂^?) and the aqueous species NO₂^? and NO₃^?. Additionally, the myeloma cells treated by positive plasma jet results in more cell apoptosis and more CD95 expression compared to negative plasma jet, indicating the impact for the cell apoptosis is more significant in the cellular response to the positive plasma jet. By comparing and analyzing the different doses of RONS to the responses of myeloma cells under positive and negative pulse plasma jet, our findings suggest the cell viability has a positive correlation with the concentration of the concentration of ONOO^? and the concentration ratio of H₂O₂ to NO₂^?, implying the high concentrations for ONOO^? and H₂O₂ might be responsible for the inactivation of myeloma cancer cells.     

Kinetics of the oxidation of diethyl sulfide in the B(OH)<Subscript>3</Subscript>-H<Subscript>2</Subscript>O<Subscript>2</Subscript>/H<Subscript>2</Subscript>O system

Data obtained for the kinetics of oxidation of diethyl sulfide (Et₂S) by hydrogen peroxide in aqueous solution catalyzed by boric acid indicate that monoperoxoborates B(O₂H)(OH) ₃ ⁻ and diperoxoborates B(O₂H)₂(OH) ₂ ⁻ are the active species. The rates of the reactions of Et₂S with B(O₂H)(OH) ₃ ⁻ and B(O₂H)₂(OH) ₂ ⁻ are 2.5 and 100 times greater than with H₂O₂. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 38–42, January–February, 2007.     

Effect of curvature of the minimum energy path upon reaction dynamics: the H2O−(2B1)→H−(1S) + OH(2Π) dissociation

The dynamics of the H₂O^?(²B₁)→H^?(¹S) + OH(²Π) dissociation has been studied on three different potential energy surfaces using a quasiclassical trajectory method in the fixed-angle approximation. The partitioning of the excess energy between translational and internal energies of the fragments appears to be strongly affected by the curvature of the minimum-energy path.     

Direct rate measurements on the reactions N + OH → NO + H And O + OH → O2 + H

Rate constants for the radical-radical reactions N + OH → NO + H (1), and O + OH → O₂ + H (2) have been measured for the first time by a direct method. In each experiment, a known concentration of N or O atoms is established in a discharge-flow system. OH radicals are then created by flash photolysis of H₂O present in the flowing gas, and the disappearance of OH is monitored by time-resolved observations of its resonance fluorescence. The experiments yield K₁ = (5.0 = 1.2) × 10^?11 cm³ molecule^?1 s^?1 and k₂ = (3.8 = 0.9) × 10^?11 cm³ molecule^?1 s^?1, for the reactions at 298 = 5 K.     

A Computational Study of the Olefin Epoxidation Mechanism Catalyzed by Cyclopentadienyloxidomolybdenum(VI) Complexes

A DFT analysis of the epoxidation of C₂H₄ by H₂O₂ and MeOOH (as models of tert‐butylhydroperoxide, TBHP) catalyzed by [Cp*MoO₂Cl] ( 1 ) in CHCl₃ and by [Cp*MoO₂(H₂O)]⁺ in water is presented (Cp*=pentamethylcyclopentadienyl). The calculations were performed both in the gas phase and in solution with the use of the conductor‐like polarizable continuum model (CPCM). A low‐energy pathway has been identified, which starts with the activation of ROOH (R=H or Me) to form a hydro/alkylperoxido derivative, [Cp*MoO(OH)(OOR)Cl] or [Cp*MoO(OH)(OOR)]⁺ with barriers of 24.9 (26.5) and 28.7 (29.2) kcal mol^?1 for H₂O₂ (MeOOH), respectively, in solution. The latter barrier, however, is reduced to only 1.0 (1.6) kcal mol^?1 when one additional water molecule is explicitly included in the calculations. The hydro/alkylperoxido ligand in these intermediates is η²‐coordinated, with a significant interaction between the Mo center and the O^β atom. The subsequent step is a nucleophilic attack of the ethylene molecule on the activated O^α atom, requiring 13.9 (17.8) and 16.1 (17.7) kcal mol^?1 in solution, respectively. The corresponding transformation, catalyzed by the peroxido complex [Cp*MoO(O₂)Cl] in CHCl₃, requires higher barriers for both steps (ROOH activation: 34.3 (35.2) kcal mol^?1; O atom transfer: 28.5 (30.3) kcal mol^?1), which is attributed to both greater steric crowding and to the greater electron density on the metal atom.     

Vitamin C: an experimental and theoretical study on the gas‐phase structure and ion energetics of protonated ascorbic acid

In order to investigate the gas‐phase mechanisms of the acid catalyzed degradation of ascorbic acid (AA) to furan, we undertook a mass spectrometric (ESI/TQ/MS) and theoretical investigation at the B3LYP/6‐31 + G(d,p) level of theory. The gaseous reactant species, the protonated AA, [C₆H₈O₆]H⁺, were generated by electrospray ionization of a 10^?3 M H₂O/CH₃OH (1 : 1) AA solution. In order to structurally characterize the gaseous [C₆H₈O₆]H⁺ ionic reactants, we estimated the proton affinity and the gas‐phase basicity of AA by the extended Cooks's kinetic method and by computational methods at the B3LYP/6‐31 + G(d,p) level of theory. As expected, computational results identify the carbonyl oxygen atom (O2) of AA as the preferred protonation site. From the experimental proton affinity of 875.0 ± 12 kJ mol^?1 and protonation entropy ΔS_p 108.9 ± 2 J mol^?1 K^?1, a gas‐phase basicity value of AA of 842.5 ± 12 kJ mol^?1 at 298 K was obtained, which is in agreement with the value issuing from quantum mechanical computations. Copyright © 2016 John Wiley & Sons, Ltd.