Extent of exchange of36Cl with CAB in strong acid medium

Aqueous chloramine-B /C₆H₅SO₂NCl Na/ solution is known to contain species like RNCl^–, RNHCl, RNCl₂, RN⁺H₂Cl, HOCl and H²⁺OCl where R=C₆H₅SO₂. The exchange studies between³⁶Cl and CAB carried out in various media by ion-exchange method indicated that there is no exchange in solution at pH7. As the pH is decreased below 7, the extent of exchange increases reaching a maximum at pH 3. 3. The exchange decreases as the acidity is increased between pH 3.3 and 1N and again the exchange increases beyong 1N. The observed increase in exchange in strong acid medium is due to the evolution of chlorine.     

Reactive collisions in quadrupole cells. 3: H/D exchange reactions of protonated aromatic amines with ND3

The H/D exchange reactions of a variety of protonated aromatic amines with ND₃ m the collision cell of a hybrid BEqQ tandem mass spectrometer have been studied. The MH⁺ ions were prepared by CH₄, t-C₄H₁₀, and NH₃ chemical ionization (CI) and, for some amines, by fast-atom bombardment (FAB). Evidence is presented that the kinetic energy of the incident ion as well as its internal energy must be dissipated by nonexchanging collisions before exchange occurs, once deactivated the MH⁺ ions exchange efficiently, which leads, in most cases, to [MHJ⁺ d _x ions m which all active hydrogens have been exchanged. The MH⁺ ion of 1,3-phenylenediamine formed by gas-phase CI exchanges only very slightly with ND₃ whereas a significant fraction of the MH⁺ ions formed by FAB exchange efficiently. This difference is rationalized in terms of dominant formation of the ring-protonated species in gas-phase CI reactions and significant formation of the N-protonated species by FAB with only the N-protonated species exchanging efficiently. Similar, although less pronounced, differences are observed for the MH⁺ ion of m-anisidine. In a number of cases apparent exchange of aromatic hydrogens also is observed. Evidence is presented for the interchange of ring and amine hydrogens in protonated aromatic amines and it is suggested that only the N-protonated species undergoes significant exchange with ND₃.     

Rhenium Complexes with p-Fluorophenylisocyanide

p-Fluorophenylisocyanide (CNPh^pF) reacts with [Re(CO)₅Br] under stepwise exchange of the carbonyl ligands depending on the conditions applied. The reaction stops with the formation of fac-[Re(CO)₃Br(CNPh^pF)₂] in boiling THF. An ongoing carbonyl exchange is observed at higher temperatures, e. g. in refluxing toluene, with the final formation of the [Re(CNPh^pF)₆]⁺ cation. The progress of the reactions has been studied by ¹⁹F NMR spectroscopy and the structures of [Re(CO)Br(CNPh^pF)₄] and [Re(CNPh^pF)₆](BPh₄) have been elucidated by X-ray diffraction.     

Reaction of ionized propene with methanol: Comparison with CH3OH2+ formation from ionized 2-methylpropanol

Methanol exchanges its hydroxyl hydrogen with deuteriums in ionized propene during the formation of protonated methanol. This exchange is attributed to the interconversion [CH₃CH?CH₂^+. HOCH₃?][CH₂ ?CHCH₂ ⁺H₂OCH₃] in single collisions. The exchange in this ion-molecule reaction is analogous to that observed in the formation of protonated methanol from ionized 2-methylpropanol, supporting the intermediacy of ion-neutral complexes in the final step of the latter reaction. Ion-molecule reactions were studied using a Fourier transform mass spectrometer.     

Adducts of Niobium (V) and Tantalum (V) Halides. XV. Ligand Exchange of the Adducts with Some Phosphoryl Compounds

The ligand exchange MX₅·L + *L?MX₅·*L + L for the octahedral adducts MX₅·L, in an inert solvent (CH₂Cl₂ or CHCl₃) with neutral ligands, proceeds via a dissociative D mechanism when M = Nb, X = Cl and L = phosphoryl compound. A dissociative interchange I_d mechanism is suggested when M = Nb or Ta, and X = F. A first order rate law and positive values for ΔS* (+4 to +14 cal K^?1 mol^?1) are observed for the exchanges on the pentachloride adducts. However, a second order rate law and large negative values for ΔS* (-15 to -24 cal K^?1 mol^?1) are found for the intermolecular neutral ligand exchange (measured by ¹H-NMR.) and for the intramolecular fluorine exchange (measured by ¹⁹F-NMR.) reactions on the pentafluoride adducts. The fluorine exchange is 2 to 5 times faster than the ligand exchange. The exchanges, on the pentachloride and on the pentafluoride adducts, are slowed down with increasing donor strength of the phosphoryl compound.     

State of Chromium in Solid Solutions of Multicomponent Bismuth Niobates with Pyrochlore Structure

Magnetic susceptibility of solid solutions of multicomponent bismuth niobates with pyrochlore structure containing chromium atoms was studied. The parameters determining the state of chromium atoms and the exchange coupling between the paramagnetic atoms were calculated. The best agreement between the experimental and theoretically calculated magnetic moments of the chromium atoms is observed on the condition that all the chromium atoms in the Bi₂MgNb₂O₉ structure are in the form of ferromagnetic exchange-coupled dimers with an exchange parameter J 18 cm^{- 1}.     

Decomposition of a cation exchange resin with hydrogen peroxide

Ion exchange resins are widely used in the field of nuclear industry. The present work aimed at the development of a method for complete decomposition of cation exchange resins with H₂O₂ in the presence of Fe³⁺ ion. The decomposition reaction proceeded at ambient temperature and decomposition time was greatly shortened with increasing concentration of Fe³⁺ ion rather than that of H₂O₂. The catalytic action of Fe³⁺ ion was suppressed with increase of HNO₃ concentration. As much as 4 g of the air-dried resin could be decomposed with 8 ml of 30% H₂O₂, and the use of about 60 ml of 30% H₂O₂ resulted in the complete decomposition of organic carbon to CO₂. Absence of any orgnaic carbon in the residual solution will simplify the final disposal.     

Study on the reactivity of In2O3 in mixtures with ammonium-zeolites

In ground mixtures of In₂O₃ and NH₄Y, incorporation of In⁺ cations into the zeolitic phase occurs upon thermal treatment by partial reductive solid-state ion exchange associated with oxidation of ammonium ions or released ammonia to N₂ and NH₂OH. Cationic InO⁺ species, created in zeolites by reductive solid-state ion exchange of In₂O₃/NH₄-zeolite mixtures in hydrogen atmosphere and subsequent oxidation of the In⁺ lattice cations by oxygen, do not undergo autoreduction up to 970 K. Reductive solid-state ion exchange easily proceeds in carbon monoxide atmosphere at temperatures between 620 and 770 K. The significance of these observations for the use of indium-containing zeolites as catalysts is discussed.     

Features of the decomposition of the neutral nitrosyl iron complexes with aryl-containing thiolate ligands in various solvents. Reaction with glutathione

The decomposition of two neutral binuclear nitrosyl iron complexes (NICs) of the µ-S structural type and general composition [Fe₂(SR)₂(NO)₄]⁰ was studied in comparison. The exchange reaction of the thiophenol or 2-aminothiophenol thiolate ligand by glutathione (GSH) in neutral NICs was studied. The reaction system was analyzed by spectrophotometry to prove the presence of a new NICs with the GS^– ligand in it. It was found that, unlike the earlier studied binuclear cationic NICs of the µ-S type and general composition [Fe₂(µ-SR)₂(NO)₄]²⁺SO₄?nH₂O with cysteamine and penicillamine ligands in which both thiolate ligands exchange by GS^–, in these neutral complexes both thiolate ligands are de-tached by only one GSH ligand is attached. A water molecule is inserted into the second free site. It is assumed that the antitumor activity of the neutral NICs can be determined not only by their NO-donor activity but also by their ability to exchange the thiolate ligand by GS^–, i.e., "to remove" GSH from the medium as in the case of cationic NICs. The discovered reaction can prevent, most likely, the S-glutathionylation of important metabolites in the presence of GSH and is very significant for metabolism of NICs.     

Ligand exchange reaction of Zn(II)-acetylacetonate complex with 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid

Ligand exchange reaction of Zn(II)-acetylacetonate complex (Zn-acac₂) with 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (H₂TPPS) has been investigated spectrophotometrically and radiometrically. The exchange reaction was observed by spectral change from H₂TPPS to Zn-TPPS or activity of⁶⁵Zn(acac)₂ extracted into the chloroform phase. The 2nd order rate constants (k ₂) for the exchange reaction at 70 °C and at pH 7.8 were found to be 32.8±2.3 and 31.2±3.2 M^–1·s^–1 from the spectrometric and radiotracer experiments, respectively. For the direct complexation of Zn(II) with H₂TPPS, a similar 2nd order rate constant (k=32.4±4.7 M^–1·s^–1) was obtained as that in the ligand exchange reaction. The activation energies (E) for the exchange and the formation of Zn-TPPS were found to be 69.3±0.2 and 69.4±0.2 kJ·mol^–1, respectively, in the temperature range from 40 to 70 °C.     

Synthesis of Y-type zeolites with high degree of Na<Superscript>+</Superscript> cation exchange for La<Superscript>3+</Superscript>

Effect of parameters of the ion exchange of Na⁺ cations for La³⁺ in Y zeolites with SiO₂/Al₂O₃ molar ratios of 5.1 and 6.0 on the degree of exchange and physicochemical properties of the resulting LaNaY samples was studied. The conditions in which deeply substituted La-forms of a Y zeolite with high degree of crystallinity can be obtained were determined.     

NMR Study of the Ligand Interchange of Hexacyclen and Hexamethylhexacyclen Complexes with TI+ Ion in 70% Methanol Solution

The exchange kinetics of TI⁺ complexes with hexacyclen and hexamethylhexacyclen were studied in 70% methanol solution by proton NMR line-shape analysis. In TI⁺-hexacyclen system, a dissociative mechanism is found to be predominant at higher temperatures, while a bimolecular pathway may become more important at lower temperatures. In contrast, the TI⁺-hexamethylhexacyclen system solely prefers a dissociative exchange mechanism in entire temperature range studied. The corresponding exchange rates and the activation parameters E_a, ΔH^?, ΔS^? and ΔG^? for the exchange have been determined, and the possible parameters controlling the exchange rates and mechanisms are discussed.     

Kinetics of the metal-ligand exchange of cadmium rhodo- and pyrroporphyrins with cobalt and zinc chlorides in organic solvents

Experimental data on electron absorption spectra (EASs) and the kinetics of substitution of Co²⁺ for the central Cd²⁺ ion in rhodoporphyrin complexes (CdRodP) in the reaction with CoCl₂ in acetonitrile (AN) and ZnCl₂ in dimethyl sulfoxide (DMSO) and the substitution of Zn²⁺ for Cd²⁺ in pyrroporphyrin complexes (CdPyrP) in the reaction with ZnCl₂ in DMSO are reported and discussed. The evolution of EASs in the reaction of metal-ligand exchange and the effective and true rate constants of the exchange reaction are reported. The activation energies and activation entropies are estimated.     

Calculating constants of the rates of the reactions of excitation,ionization, and atomic exchange: A model of a shock oscillator with a change of the Hamiltonian of the system

A new model for calculating the rates of reactions of excitation, ionization, and atomic exchange is proposed. Diatomic molecule AB is an unstructured particle M upon the exchange of elastic-vibrational (VT) energy, i.e., a model of a shock forceful oscillator with a change in Hamiltonian (SFOH). The SFOH model is based on the quantum theory of strong perturbations. The SFOH model allows generalization in simulating the rates of the reactions of excitation, ionization, and atomic exchange in the vibrational-vibrational (VV) energy exchange of diatomic molecules, and the exchange of VV- and VT-energy of polyatomic molecules. The rate constants of the excitation of metastables A ³Σ _u ⁺, B ³Π _g , W ³Δ _u , B′³Σ _u ^-, a′³Σ _u ^-, and the ionization of a nitrogen molecules from ground state X²Σ _g ⁺ upon a collision with a heavy structureless particle (a nitrogen molecule), are found as examples.     

Magnetochemistry of dimers with iron group ions

General theory of matrix interactions of dimers of iron group ions is considered. Equations for calculation of matrix elements of the exchange energy of dimers and equations for calculation of the magnetic moments of dimers of different d ⁿ configurations and different exchange parameters are reported. The energies of the spin states of dimers are calculated with inclusion of exchange interactions of the first J ₀ and second J ₂ orders, and energy state diagrams for dimers with different spins and exchange energies are reported. For heterospin dimers, equations for calculation of the magnetic moment ?? and magnetic susceptibility ?? are introduced, and for homospin dimers, analytical formulas of calculation are presented. The tables of magnetic moments are calculated and their diagrams as a function of J ₀ for homospin dimers with spins S = 5/2, 2, 3/2, 1, and 1/2 are given. The experimental data are interpreted for Co²⁺ dimers as an example: the experimental and theoretical dependences of ?? and ?? on temperature are considered.     

Solvent extraction studies of radioisotopic exchange of36Cl with Chloramine-B in strong acid medium

Exchange studies with³⁶Cl and Chloramine-B in strong acid medium revealed that the extent of exchange is less than that occurs at pH 3.3 indicating the formation of a new species of Chloramine-B which is not participating in the exchange reaction and this has been confirmed by conductometric titration of Chloramine-B with dilute solutions of H₂SO₄, HCl, HClO₄ and CH₃COOH.     

Observation of zwitterion formation in the gas-phase H/D-exchange with CH<Subscript>3</Subscript>OD: Solution-phase structures in the gas phase

Infrared spectroscopy of gas-phase singly deuterated [Trp+K]⁺ (formed by H/D exchange with CH₃OD) shows that some (∼20%) kinetically stable zwitterionic (ZW) conformer is formed, based on the diagnostic antisymmetric CO stretch of the deprotonated carboxylate moiety, υ_as(CO₂⁻), at 1680 cm⁻¹. A majority of the deuterated [Trp+K]⁺ is found to be in the charge solvation (CS) conformation, with deuterium exchange occurring on both the acid and amino groups, which is consistent with H/D scrambling. Interestingly, H/D exchange with the more basic ND₃ reagent did not result in the stabilization of a kinetically stable zwitterion, although it is not clear yet what causes this observation. The result for CH₃OD shows that H/D exchange can in fact alter the structure of the analyte and, hence, care needs to be taken when interpreting gas-phase H/D exchange studies. Moreover, this result shows the possibility of forming solution-phase structures that are thermodynamically disfavored in the gas phase, thus opening a new area of study.     

Aromatic protonation—4: On the 1H-2H exchange of three 9-n-alkylanthracenes on reaction with CF3CO2[2H] and FSO3[2H]

The reactions of 9-methyl-, 9-ethyl- and 9-propyl-anthracene with CF₃CO₂[²H] in C[²H]Cl₃ and with FSO₃[²H] in SO₂ClF have been investigated. Using 4 equivalents of CF₃CO₂[²H] at 50° ¹H-²H exchange was observed only for the 10-H and the side-chain α-hydrogens, and on using 8 and 12 equivalents at 50° also for the aromatic α-hydrogens. Treatment of the substrates with FSO₃[²H] at -60° leads to the stable 9-alkyl-[10-²H]-10-anthracenium ions. On warming up to ?25° a slow ¹H-²H exchange of only the 10-¹H of these anthracenium ions is observed. A mechanism for the ¹H-²H exchange of the aromatic and the side-chain α-hydrogens of the 9-alkylanthracenes is presented.     

Detailed Description of Pulse Isotopic Exchange Method for Analyzing Oxygen Surface Exchange Behavior on Oxide Ion Conductors

A novel pulse ¹⁸O-¹⁶O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an ¹⁸O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of ¹⁸O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate ¹⁸O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues ¹⁸O₂, ¹⁶O¹⁸O, and ¹⁶O₂ in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350?900 oC. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ(BSCF) and La₂NiO_4+δ the reaction is limited by the apparent rate of dissociative adsorption of O₂ molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ∽800 oC to rate-limitations by O₂ dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.     

Structural characterization of ammonium molybdophosphate with different amount of cesium adsorption

Powdered crystal AMP was synthesized by precipitation method and different Cs-loading AMP samples were prepared in this work. They were studied by modern methods of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) to gain a better understanding of the ion exchange mechanism of ammonium molybdophosphate (AMP). The XRD patterns combined with the FT-IR analysis indicate that the Keggin structure is retained after Cs adsorption, while the changes of certain characteristic diffraction peaks show crystal lattice distortion caused by the mismatching sizes of Cs⁺ and [NH₄]⁺. The TGA showed that the weight percent of H₂O and [NH₄]⁺ decreases as the amount of Cs adsorbed onto AMP increases, which corresponds with the theory of isomorphous exchange.