Determination of trace amount of IO 3 − with KIO3-KBr-(DBS-arsenazo) system by spectrophotometry

In the medium of 0.45 M nitric acid IO ₃ ^? oxidizes KBr to produce Br₂, which oxidizes DBS-arsenazo (DBS-ASA) to decolour. Based on this principle, a new method for the determination of iodate has been developed. The KIO₃-KBr-(DBS-ASA) system presents a maximum absorption at 530 nm. At that wavelength, Beer’s law is obeyed over the range of 0.050–0.60 μg/mL of IO ₃ ^? presenting a linear relationship. The apparent molar absorptivity is 1.75 × 10⁵ L/mol cm and the detection limit is 0.048 μg/mL. This method has been successfully applied to the determination of IO ₃ ^? content in the iodized table salt sample with good results.     

Extraction-photometric selective determination of trace perchlorates in potable waters

A method is proposed for the selective photometry determination of perchlorates in potable water with a detection limit of 2×10^?3 mg/L is proposed based on the extraction of its ion pair with the astrafloxin cation and absorbance measurements at 540 nm. The following ratios of matrix ions are acceptable (in parentheses): ClO^?, ClO ₂ ^? , ClO ₃ ^? , BrO ₃ ^? (500); I^? (1000); IO ₃ ^? (7000); HCO ₃ ^? , Cl^?,SO ₄ ^2? , NO ₃ ^? , Br^?, Na⁺, K⁺, Ca²⁺, Mg²⁺ (10000). The relative error of determination for ClO ₄ ^? is 20% in the range 4 × 10^-3-1 × 10^?2 mg/L and 10% in the range 1 × 10^-2–5 × 10^?2 mg/L.     

Isomorphous crystal structures of 4,7,13,16,21,24-hexaoxo-1,10-diaziniabicyclo[8.8.8]·hexacosane bis(tribromide) and bis(bromoiodide)

Two compounds, 7,13,16,21,24-hexaoxa-1,10-diazoniabicyclo[8.8.8]hexacosane bis(tribromide) and bis(bromodiiodide) — [H₂(Crypt-222)]²⁺·2Br ₃ ^? (I) and [H₂(Crypt-222)]²⁺·1.45(BrI₂)^?·0.4(Br₂I)^?·0.15 I ₃ ^? (II) — are prepared and characterized by single crystal XRD; the refinement of the second compound was more accurate. Isomorphous monoclinic structures (I, space group C2/c, Z = 4, a = 12.090, b = 15.833 Å, c = 15.732 Å, β = 95.83°; II, a = 12.548 Å, b = 16.417 Å, c = 15.748 Å, β = 94.53°) are solved by a direct method and refined in the anisotropic full-matrix approximation to R = 0.057 (I) and 0.044 (II) using all 2635 (I) and 2852 (II) measured independent reflections (automated CAD-4 diffractometer, λMoK _α). In the structures of I and II one of the trihalide anions sits at the inversion center i(000), and the second trihalide anion and the dication [H₂(Crypt-222)]²⁺ are situated at crystallographic axis 2. In the structure of II iodine is located in the center of trihalide anions, while the terminal atoms are disordered and are represented by a statistical combination of iodine and bromine atoms.     

Determination of nitrite, nitrate, bromide, and iodide in seawater by ion chromatography with UV detection using dilauryldimethylammonium-coated monolithic ODS columns and sodium chloride as an eluent

A method was developed for determination of inorganic anions, including nitrite (NO ₂ ^? ), nitrate (NO ₃ ^? ), bromide (Br^?), and iodide (I^?), in seawater by ion chromatography (IC). The IC system used two dilauryldimethylammonium bromide (DDAB)-coated monolithic ODS columns (50?×?4.6?mm i.d. and 100?×?4.6?mm i.d.) connected in series for separation of the ions. Aqueous NaCl (0.5?mol/L; flow rate, 3?mL/min) containing 5?mmol/L phosphate buffer (pH 5) was used as the eluent, and detection was with a UV detector at 225?nm. The monolithic ODS columns were coated and equilibrated with a 1-mmol/L DDAB solution (in H₂O/methanol, 90:10 v/v). The hydrophilic ions (NO ₂ ^? , NO ₃ ^? , and Br^?) were separated within 3?min and the retention time of I^? was 16?min. No interferences from matrix ions, such as chloride and sulfate ions, were observed in 35?‰ artificial seawater. The detection limits were 0.6?μg/L for NO ₂ ^? , 1.1?μg/L for NO ₃ ^? , 70?μg/L for Br^?, and 1.6?μg/L for I^? with a 200-μL sample injection. The performance of the coated columns was maintained without addition of DDAB in the eluent. The IC system was successfully applied to real seawater samples with recovery rates of 94–108?% for all ions.

Oxidation and reductive bromination of Bis(4-tert-butylphenyl)aminoxyl

One-electron oxidation of bis(4-tert-butylphenyl)aminoxyl with antimony pentachloride and bromine leads to the formation of oxoammonium salts with anions SbCl ₆ ^? and Br ₃ ^? respectively. The salt with the Br ₃ ^? anion converted at heating into a mixture of bromodiphenylamines which formed also from the aminoxyl as a result of previously unknown reaction of three-electron reductive bromination. The mechanisms of these reactions were assumed.     

Hydration numbers of ions in aqueous solutions of KOH, KCl, KI, and KIO3 according to refractometric data

Ion hydration in aqueous solutions of KOH, KCl, KI, and KIO₃ was studied by refractometry. The sum of the hydration numbers of the potassium ion and each anion in these compounds and the hydration numbers of OH^?, Cl^?, I^?, and IO ₃ ^? anions were determined by the Lorentz-Lorenz equation at different salt concentrations. The model suggests that the polarizability of the hydrated ion is proportional to the cube of the ion radius and the volume of the hydrated ion equals the sum of the nonhydated ion and hydration shell volumes. The hydration numbers of the anions calculated by the proposed procedure increase with their radii in the sequence: OH^?, Cl^?, I^?, and IO ₃ ^? .     

A selective fluorescent and colorimetry competition assay for fluoride ions in DMSO media based on 4-chloro-2,6-bis(hydroxymethyl) phenol

We report here a selective, efficient and very simple receptor which can easily detect F^? in the presence of a wide range of other anions [Cl^?, Br^?, I^?, HSO ₄ ^? , NO ₃ ^? , Acetate (AcO ^?) and Benzoate (BzO ^?)] by use of colorimetric or fluorometric detection. 4-Chloro-2,6-bis(hydroxymethyl) phenol (CBHMP) is a simple and available phenolic receptor having no special chromophoric function. In this colorimetric method, naked-eye detection of F^? with CBHMP is described. Interestingly, fluorometric detection of F^? is also possible by highly selective fluorescent quenching response CBHMP in dimethyl sulfoxide (DMSO) media.     

Using epichlorohydrin for a simultaneous increase of functional group hydrophilicity and spatial separation from the matrix of anion exchangers for ion chromatography

To increase the efficiency of anion exchangers based on copolymers of styrene and divinylbenzene in ion chromatography a new method for spatial separation and hydrophilization of functional groups using epichlorohydrin is suggested. Synthesis consists of acylation of a matrix by acetic anhydride, reductive amination by methylamine hydrochloride, alkylation of the aminated phase using epichlorohydrin, amination by dimethylamine at the terminal chlorine atom, and quaternization of the terminal amino group with epichlorohydrin. The obtained anion exchangers make it possible to simultaneously determine eight anions (F^?, HCOO^?, Cl^?, NO ₂ ^? Br^?, N ₃ ^? HPO ₄ ^3? and SO ₄ ^2? ) and demonstrate high efficiency (more than 62000 N/m for HPO ₄ ^2? ) in a suppressed ion-chromatography mode.     

Octadecylamine cobalt(III) dimethyl glyoximato complexes: synthesis,thermodynamics of micellization,steady-state photolysis and biological activities

A new class of surfactant–cobalt(III) complexes of the type trans-[Co(DH)₂(OA)X], where DH = dimethylglyoxime, OA = octadecylamine, X = Cl^?, Br^?, I^?, N₃ ^?, NO₂ ^?, SCN^? or OA, were synthesized and characterized by physicochemical and spectroscopic methods. The critical micelle concentration (CMC) values of these surfactant–cobalt(III) complexes in ethanol solution were obtained by measuring absorption at ~250 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG _m ⁰ , ΔH _m ⁰ and ΔS _m ⁰ ). Steady-state photolysis and cyclic voltammetry of the complexes were studied. The surfactant–cobalt(III) complexes were screened for their antibacterial and antifungal activities against various microorganisms.     

The conformational changes of 5SrRNA from lupin seeds in presence of ClO 4 − , NO 3 − , Br−, BF 4 − , SO 4 2− , Cl−, COO− anions by adiabatic scanning calorimetry

The results of calorimetric studies of 5SrRNA solutions isolated from lupin seeds in the pressence of the ClO ₄ ^? , NO ₃ ^? , Br ₄ ^? , SO ₄ ^2? , Cl^?, COO^? (maleic and fumaric acids) anions were reported. The plots of calorimetric curves, enthalpy of conformational changes of two state transitions were presented. Using the deconvolution method proposed by Freire and Biltonen the elementary transitions were distinguished and discussed.     

EXAFS study of spin transition effect on the spatial and electronic structure of Fe(II) complexes with triazoles

EXAFS spectroscopy is used to investigate the characteristic features of the spatial and electronic structure of the polynuclear Fe(II) complexes Fe(ATR)₃A₂ (where A is the NO ₃ ^? , BF ₄ ^? , Br^?, or ClO ₄ ^? anion and ATR is 4-amino-1,2,4-triazole) and their magnetically diluted phases Fe_xZn_1?x(ATR)₃(NO₃)₂. The absolute distances from Fe and Zn to the surrounding atoms are determined at temperatures higher and lower than the spin transition point. In all complexes, the spin transition is accompanied by significant changes in the local environment of Fe atoms, while in the magnetically diluted phases the surrounding of zinc remains unchanged. It is shown that addition of Zn atoms distorts the triazole rings in the low-spin state of the complexes. No localized anions were revealed within 3.3 Å from the Fe and Zn atoms. It is shown that a decrease in the spin transition temperature correlates with an increase in Fe?N distances in the low-spin complexes due to magnetic dilution and substitution of anions in the series NO ₃ ^? , BF ₄ ^? , Br^?, ClO ₄ ^? of ATR-containing complexes.     

Isomery of [Re6S6Br8] and [Re6S5Br9] Units in a Rhenium Cluster Thiobromide: Experimental and Theoretical Approaches

The rhenium cluster thiobromide Cs_1.95(1)Re₆S_5.82(3)Br_8.19(3), belonging to the solid solution Cs₂Re₆S₆Br₈–CsRe₆S₅Br₉, crystallizes in the trigonal system (P31c, a = 10.001(5) Å and c = 14.676(5) Å). It is built up from [Re₆L ₈ ⁱ ]Br ₆ ^a cluster units in which sulphur and bromine are randomly distributed on inner position (Lⁱ). From the structural refinement performed using single-crystal X-ray diffraction data, the isomers of the [Re₆Sⁱ ₆Br ₂ ⁱ ] and [Re₆S ₅ ⁱ Br ₃ ⁱ ] cluster cores present in the structure have been unambiguously determined, due to the non-centro symmetry of the structure. Density functional theory calculations have been performed for all possible di- and tri-substituted isomers in order to confirm experimental analyses. Slight differences between the stability of di-substituted and tri-substituted cluster unit isomers built from Mo₆ cluster and Re₆ clusters are evidenced.     

Dynamic solvation effects on surface-impact dissociation of I 2 - (CO2)n

Surface-impact dissociation of I ₂ ^- (CO₂)n was studied by a molecular dynamics simulation in comparison with the experimental results. The branching fraction, ? _dis, of the I ₂ ^- dissociation was calculated as a function of the parent cluster size, n. This computational result reproduces the experimental one. We calculated a number of the I ₂ ^- dissociation events starting from given initial orientations. The most favorable molecular orientation obtained supports the wedge effect in which a CO₂ molecule located at the waist position of the I ₂ ^- core ion splits the I ₂ ^- bond as if a piece of wood is split by a mechanical thrust against a wedge. The time profile of the wedge action calculated for the I ₂ ^- (CO₂) impact shows that more than 20 % of the collision energy is converted to the vibrational energy of the I ₂ ^- .     

Crystal and molecular structure of tetraphenylarsonium diiodobromide

Complex formation of tetraphenylarsonium bromide with molecular iodine in a chloroform solution was studied. Spectrophotometry with the use of the medium iodine number function was used to estimate the limiting number of iodine molecule coordinated with the bromide ion in the solution and the stability complex of the complex. According to X-ray diffraction data, the cation and anion of [(C₆H₅)₄As]⁺I₂Br^? in crystal reside in a special position on the C ₂ axis, and a superposition of the I ₃ ^? and Br₂I^? anions is observed, with ratios of 0.526 and 0.474, respectively. The resulting salt is isostructural to reported tetraphenylphosphonium interhalides.     

Jodometrische Titration von Perbromat (Bestimmung von BrO 4 − und BrO 3 − nebeneinander)

Perbromate is reduced to bromate by iodide in weakly alkaline solution (pH 7–9) at 100° C. The formation of iodine in the hot solution is prevented by addition of an excess of arsenite, which is finally titrated with a I₂-solution for the determination of BrO ₄ ^? . The total BrO ₃ ^? content is then determinated by titration of the acidified solution with thiosulphate. From both titrations the initial content of BrO ₃ ^? is obtained. Both methods are simple and accurate. A direct method for the determination of BrO ₃ ^? in solutions containing BrO ₄ ^? is also described.     

Radical-induced destruction of diethyl phthalate in aqueous solution: kinetics, spectral properties, and degradation efficiencies studies

In this work, the reactions of ^?OH, e _aq ^? , and SO ₄ ^?? with diethyl phthalate (DEP) were investigated in aqueous solution by pulse radiolysis, and degradation efficiencies of DEP with ^?OH and e _aq ^? were evaluated in water using steady-state radiolysis as well. The absolute rate constants of ^?OH, e _aq ^? , and SO ₄ ^?? with DEP were determined as 2.3 × 10⁹, 1.0 × 10¹⁰, and 1.0 × 10⁸ M^?1 s^?1, respectively. The degradation efficiencies for the ^?OH and e _aq ^? reactions were 81 and 33 %, respectively. Transient absorption spectra were observed for the intermediate radicals produced by ^?OH, e _aq ^? , and SO ₄ ^?? reactions. The results suggested that e _aq ^? transferred to the ester group, resulting in the formation of DEP radical anions. In contrast, ^?OH and SO ₄ ^?? added predominantly to the aromatic ring of DEP, forming the corresponding ^?OH adducts. The fundamental mechanistic parameters and degradation efficiencies derived from these results were significant for evaluations and applications of advanced oxidation processes.     

Thermal and kinetic studies of epoxidized natural rubber in lithium salts-epoxidized natural rubber polymer electrolytes

The thermal and kinetic studies of epoxidized natural rubber (ENR) and its polymer electrolytes, LiX/ENR PEs, (where X = ClO ₄ ^? , CF₃SO ₃ ^? , COOCF ₃ ^? , I^?, and BF ₄ ^? ) were carried out using thermogravimetric analysis at different heating rates. The thermal behaviors for LiX/ENR PEs are closely related to the morphology and interactions between the LiX and ENR chains. The LiCF₃SO₃, LiCOOCF₃, and LiI form pseudo-crosslinking within the ENR; their thermal behavior resembled purified ENR. The LiClO₄ tends to form aggregates within the ENR. This phenomenon has promoted a much earlier decomposition of epoxide in the ENR. The occurrence of ring-opening and complexation or cross-linking reactions in and between the ENR chains in the LiBF₄/ENR has produced a thermally stable macrostructure. The activation energy for the thermal degradation (E _d) of purified ENR was 239.8 and 239.9 kJ mol^?1 using Kissinger and FWO methods, respectively. According to the Coats–Redfern method, the degradation mechanism of purified ENR follows the F₁ type model, while the Criado method revealed that the degradation starts with F₁ followed by D₃ type models. The E _d for LiX/ENR (X = COOCF ₃ ^? , CF₃SO ₃ ^? , I^?, and BF ₄ ^? ) PE’s obtained via the Kissinger method are 258.5, 257.0, 251.0, and 198.9 kJ mol^?1, respectively, and the corresponding E _d values obtained by FWO are 236.0, 223.6, 349.7, and 206.6 kJ mol^?1, respectively. The degradation of ENR in these PEs followed the D₃ type model. However, for LiClO₄/ENR, the presence of two distinct degradations of ENR gave two E _d values. These are 174.5 and 234.7 kJ mol^?1 using Kissinger and 117.8 and 293.6 kJ mol^?1 using FWO method. The degradation mechanism of ENR in the LiClO₄/ENR PE was similar to purified ENR that is F₁ followed by D₃ type models.     

Periodate ion as an oxidant in indicator reactions with aromatic amines

The kinetics of 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation by sodium periodate in an aqueous solution was studied. For the auto-acceleration regime, the experimental data correspond to the kinetic equation w _t = k[P] _t ^1/2 [IO ₄ ^? ] _t ^1/2 [TMB]₀, where w _t is the accumulation rate of the meriquinoid product (P) of TMB oxidation and [P]_t and [IO ₄ ^? ]_t are the concentrations of product P and periodate, respectively, at time t. A radical chain mechanism was proposed; the mechanism explains the experimental kinetic equation and complies with the observed inhibiting effect of metal ions (Zn, Cd) in this reaction.     

Gemischt quantenmechanisch-statistische Modellrechnungen nach der Einzentrenmethode an Wasserstoffverbindungen tetraedrischer Symmetrie von Elementen der III., IV. und V. Hauptgruppe

Using a one-center-method, treating the inner shells statistically, the valence-shell, however, by quantum mechanics, the equilibrium internuclear distances and total molecular energies have been computed for CH₄, SiH₄, GeH₄, SnH₄, PbH₄, BH ₄ ^? , AlH ₄ ^? , GaH ₄ ^? , InH ₄ ^? , TlH ₄ ^? , NH ₄ ⁺ , PH ₄ ⁺ , AsH ₄ ⁺ , SbH ₄ ⁺ , and BiH ₄ ⁺ . The results are in good agreement with experimental data as well as with theoretical values.     

Boric acid

pH ranges of existence of boric acid and its ionic species H₂BO ₃ ^? , HBO ₃ ^2? , BO ₃ ^3? , and B(OH) ₄ ^? in aqueous solutions are calculated using Mathcad software package.