Rhodium(III) as a homogeneous catalyst for the oxidative decolorization of ethyl orange with aqueous acidic chloramine-T: a spectrophotometric, kinetic and mechanistic study

The kinetics and mechanism of sodium N-chloro-p-toluenesulfonamide oxidative decolorization of ethyl orange (EO) in aqueous perchloric acid have been studied at 303 K in the presence of rhodium(III) chloride as catalyst. The reaction exhibits first-order dependence on [EO]_o and a fractional-order dependence on [CAT]_o, [H⁺] and [Rh^III]. The dielectric effect is positive. The stoichiometry of the reaction was found to be 1:1, and the oxidation products of EO were identified as N-(4-diethylamino-phenyl)-hydroxylamine and 4-nitroso-benzenesulfonic acid. The rhodium(III)-catalyzed reaction is about fourfold faster than the uncatalyzed reaction. The proposed mechanism and derived rate law are in agreement with the observed kinetic results.     

Ruthenium(III)-catalyzed and uncatalyzed kinetic studies on the oxidation of sulfanilic acid by chloramine-T in perchloric acid medium: a mechanistic approach

The kinetics of the oxidation of sulfanilic acid (SAA) by sodium N-chloro-p-toluenesulfonamide (CAT) in the presence and absence of ruthenium(III) chloride have been investigated at 303 K in perchloric acid medium. The reaction shows a first-order dependence on [CAT]_o and a non-linear dependence on both [SAA]_o and [HClO₄] for both the ruthenium(III)-catalyzed and uncatalyzed reactions. The order with respect to [Ru^III] is unity. The effects of added p-toluenesulfonamide, halide, ionic strength, and dielectric constant have been studied. Activation parameters have been evaluated. The rate of the reaction increases in the D₂O medium. The stoichiometry of the reaction was found to be 1:1 and the oxidation product of SAA was identified as N-hydroxyaminobenzene-4-sulfonic acid. The ruthenium(III)-catalyzed reactions are about four-fold faster than the uncatalyzed reactions. The protonated conjugate acid (CH₃C₆H₄SO₂NH₂Cl⁺) is postulated as the reactive oxidizing species in both the cases.     

Ruthenium(III)-catalyzed mechanistic studies of oxidation of benzhydrols by sodium N-chloro-p-toluenesulfonamide in HCl medium

The kinetics of oxidation of benzhydrol and its p-substituted derivatives (YBH, where Y=H, Cl, Br, NO₂, CH₃, and OCH₃) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT), catalyzed by ruthenium(III) chloride, in the presence of hydrochloric acid in 30% (v/v) MeOH medium has been studied at 35°C. The reaction rate shows a first-order dependence on [CAT]_O and a fractional-order each on [ YBH]_O, [Ru(III)], and [H⁺]. The reaction also has a negative fractional-order (−0.35) behavior in the reduction product of CAT, p-toluenesulfonamide (PTS). The increase in MeOH content of the solvent medium retards the rate. The variation of ionic strength of the medium has negligible effect on the rate. Rate studies in D₂O medium show that the solvent isotope effect, k′H₂O/k′D₂O, is equal to 0.60. Proton inventory studies have been made in H₂O(SINGLEBOND)D₂O mixtures. The rates correlate satisfactorily with Hammett σ relationship. The LFE relationship plot is biphasic and the reaction constant ρ=−2.3 for electron donating groups and ρ=−0.32 for electron withdrawing groups at 35°C. Activation parameters ΔH^≠, ΔS^≠, and ΔG^≠ have been calculated. The parameters, ΔH^≠ and ΔS^≠, are linearly related with an isokinetic temperature β=334 K indicating enthalpy as a controlling factor. A mechanism consistent with the observed kinetics has been proposed. © 1997 John Wiley & Sons, Inc.     

Kinetic and mechanistic studies of indigocarmine oxidation by chloramine-T and chlorine in acidic buffer media

Oxidations of indigocarmine (IC) by chloramine-T (CAT) and aqueous chlorine (HOCl) in acidic buffer media, pH 2–6, have been kinetically studied at 30°C using spectrophotometry. The CAT reaction rate shows a first-order dependence on [IC]₀ and an inverse fractional order on [p-toluenesulfonamide]. The effect of [CAT] on the rate is strongly pH dependent with a variable order of 1–2 on [CAT]₀ in the pH range 6–2. The chlorine reaction rate follows first-order in [IC]₀ and [HOCl]₀ each in the pH range 6–2. Addition of halide ions and variation of ionic strength of the medium have no influence on the reaction rate. There is a negative effect of dielectric constant of the solvent. The kinetics of the IC oxidation with CAT at pH 6 and of that with HOCl at pHs 2–6 are similar suggesting similarity in their rate determining steps. A two-pathway mechanism for the CAT reaction and a one-pathway mechanism for the HOCl reaction, consistent with the kinetic data, have been proposed. Activation parameters have been calculated using the Arrhenius and Erying plots. © 1995 John Wiley & Sons, Inc.     

Kinetic and mechanistic studies of oxidation of arginine,histidine, and threonine in alkaline medium by N-chloro-N-sodio-p-toluenesulfonamide

The kinetics of oxidation of arginine, histidine, and threonine by chloramine-T (CAT) have been investigated in alkaline medium at 35°C. The rates are first order in both [CAT] and [amino acid] and inverse fractional order in [OH^?] for arginine and histidine. The rate is independent of [OH^?] for threonine. Variation of ionic strength and addition of the reaction product, p-toluenesulfonamide, or Cl^? ions had no effect on the rate. A decrease of the dielectric constant of the medium by adding methanol decreased the rate with arginine, while the rates increased with histidine and threonine. The solvent isotope effect was studied using D₂O. (k_obs)/(k_obs) was found to be 0.55 and 0.79 for arginine and histidine, respectively. The reactions were studied at different temperatures, and activation parameters have been computed. The oxidation process in alkaline medium, under conditions employed in the present investigations, has been shown to proceed via two paths, one involving the interaction of RNHCl (formed rapidly from RNCl^?), with the amino acid in a slow step to form monochloroamino acid, which subsequently interacts with another molecule of RNHCl in a fast step to give the products, p-toluenesulfonamide (RNH₂), and the corresponding nitrile of the amino acid (R'CN). The other path involves the interaction of RNCl^? with the amino acid in a similar way to give RNH₂ and R'CN. Mechanisms proposed and the derived rate laws are consistent with the observed kinetics. The rate constants predicted using the derived rate laws, as [OH^?] varies, are in excellent agreement with the observed rate constants, thus justifying these rate laws and hence the proposed mechanistic schemes.     

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene in the presence of p-tert-butylcalix[6]arene and p-tert-butylcalix[8]arene

From extraction experiments and ??-activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3A^?(aq) + L(nb) ? EuL³⁺(nb) + 3A^?(nb) taking part in the two-phase water?Cnitrobenzene system (A^? = CF₃SO₃ ^?; L = p-tert-butylcalix[6]arene, p-tert-butylcalix[8]arene; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated for a temperature of 25 °C as log ?? _nb(EuL³⁺) = 6.4 ± 0.1 (L = p-tert-butylcalix[6]arene) and log ?? _nb(EuL³⁺) = 11.3 ± 0.1 (L = p-tert-butylcalix[8]arene).     

Kinetics and mechanism of the redox reaction between malachite green and iron(III) in aqueous and micellar media

The kinetics of the oxidation of malachite green (MG⁺) by Fe(III) were investigated spectrophotometrically by monitoring the absorbance change at 618 nm in aqueous and micellar media at a temperature range 20–40 °C; I = 0.10 mol dm^?3 for [H⁺] range (2.50–15.00) × 10^?4 mol dm^?3. The rate of reaction increases with increasing [H⁺]. The reaction was carried out under pseudo-first-order conditions by taking the [Fe(III)] (>10-fold) the [MG⁺]. A mechanism of the reaction between malachite green and Fe(III) is proposed, and the rate equation derived from the mechanism was consistent with the experimental rate law as follows: Rate = (k ₄ + K ₁ k ₅[H⁺]) [MG⁺][Fe(III)]. The effect of surfactants, such as cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecylsulfate (SDS, an anionic surfactant), on the reaction rate has been studied. CTAB has no effect on the rate of reaction while SDS inhibits it. Also, the effect of ligands on the reaction rate has been investigated. It is proposed that electron transfer proceeds through an outer-sphere mechanism. The enthalpy and the entropy of the activation were calculated using the transition state theory equation.     

Kinetics of oxidation of pantothenic acid by chloramine‐T in perchloric acid and in alkaline medium catalyzed by OsO4: A mechanistic approach

Kinetics of oxidation of pantothenic acid (PA) by sodium N‐chloro‐p‐toluenesulfonamide or chloramine‐T (CAT) in the presence of HClO₄ and NaOH (catalyzed by OsO₄) has been investigated at 313 K. The stoichiometry and oxidation products are same in both media; however, their kinetic patterns were found to be different. In acid medium, the rate shows first‐order dependence on [CAT]_o, fractional‐order dependence on [PA]_o, and inverse fractional‐order on [H⁺]. In alkaline medium, the rate shows first‐order dependence each on [CAT]_o and [PA]_o and fractional‐order dependence on each of [OH^?] and [OsO₄]. Effects of added p‐toluenesulfonamide and halide ions, varying ionic strength, and dielectric constant of medium as well as solvent isotope on the rate of reaction have been investigated. Activation parameters were evaluated, and the reaction constants involved in the mechanisms have been computed. The proposed mechanisms and the derived rate laws are consistent with the observed kinetics. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 201–210, 2005     

Reduction Reaction of the Copper(II) Complex Bearing 1,3-Di(pyridine-2-carboxaldimino)propane (pitn) by Decamethylferrocene in Acetonitrile

The reduction reaction of the Cu(II)–pitn complex (pitn = 1,3-di(pyridine-2-carboxaldimino)propane) by decamethylferrocene [Fe(Cp*)₂] was examined in acetonitrile. The observed pseudo-first-order rate constants exhibited saturation kinetics with increasing excess amount of [Fe(Cp*)₂]. Detailed analyses revealed that the reaction is controlled by a structural change prior to the electron transfer step, rather than a conventional bimolecular electron transfer process preceded by ion pair (encounter complex) formation. The rate constant for the structural change was estimated to be 275 ± 13 s^?1 at 298 K (?H* = 33.3 ± 1.0 kJ·mol^?1, ?S* = 86 ± 5 J·mol^?1·K^?1), which is the fastest among gated reactions involving CuN₄ complexes. It was confirmed by EPR measurement and Conflex calculations that the dihedral angle between the two N–N planes is significantly large (40°) in solution whereas it is merely 17.14° in the crystal.     

Theoretical consideration of the anomalous temperature dependence of the surface tension of pure liquid gallium

The surface tension of pure liquid gallium in the temperature range 303–503 K (303 K is the melting point) was previously measured using the noninvasive method of capillary wave spectroscopy (CWS). The result of this experiment showed that the value of surface tension increases from 303 to 345 K indicating a negative surface excess entropy (S ^σ), and decreases linearly from ~345 to 503 K confirming a negative slope, and thus a positive S ^σ. This unusual behavior of Ga is not known for other liquid metals such as Bi, Pb, Hg, Sn and Al. The reported experimental behavior is modeled here. A theoretical equation for calculating the surface tension of liquid Ga, based upon formulating a proper partition function that includes the rotational part, is derived and described. The theory predicted no maximum in the temperature-dependence of the surface tension, as seen in the experiment, where the analysis was done over a large temperature range (325–503 K). The value obtained from this mathematical expression indicates that the temperature variation of surface tension has no positive slope within the temperature range 303–345 K. At T > 345 K, the surface tension shows the usual linear temperature-dependence with a negative slope. Therefore, the equation is only applicable for the latter temperature range. A comparison between the theoretical and experimental values of surface tension of liquid Ga is discussed.     

Low-Energy Collision-Induced Dissociation Mass Spectra of Protonated p-Toluenesulfonamides Derived from Aliphatic Amines

Collision-induced fragmentation of protonated N-alkyl-p-toluenesulfonamides primarily undergo either an elimination of the amine to form CH₃-(C₆H₄)-SO₂ ⁺ cation (m/z 155) or an alkene to form a cation for the protonated p-toluenesulfonamide (m/z 172). To comprehend the fragmentation pathways, several deuterated analogs of N-decyl-p-toluenesulfonamides were prepared and evaluated. Hypothetically, two mechanisms, both of which involve ion-neutral complexes, can be envisaged. In one mechanism, the S–N bond fragments to produce an intermediate [sulfonyl cation/amine] complex, which dissociates to afford the m/z 155 cation (Pathway A). In the other mechanism, the C–N bond dissociates to produce a different intermediate complex. The fragmentation of this [p-toluenesulfonamide/carbocation] complex eliminates p-toluenesulfonamide and releases the carbocation (Pathway B). Computations carried out by the Hartree-Fock method suggested that the Pathway B is more favorable. However, a peak for the carbocation is observed only when the carbocation formed is relatively stable. For example, the spectrum of N-phenylethyl-p-toluenesulfonamide is dominated by the peak at m/z 105 for the incipient phenylethyl cation, which rapidly isomerizes to the remarkably stable methylbenzyl cation. The peaks for the carbocations are weak or absent in the spectra of most of N-alkyl-p-toluenesulfonamides because alkyl carbocations, such as the decyl cation, rearrange to more stable secondary cations by 1,2-hydride and alkyl shifts. The energy freed is not dissipated, but gets internalized, causing the carbocation to dissociate either by transferring a proton to the sulfonamide or by releasing smaller alkenes to form smaller carbocations. The loss of the positional integrity in this way was proven by deuterium labeling experiments.

Low-temperature heat capacity and thermodynamic parameters of γ-aminobutyric acid

Thermodynamic properties of γ-aminobutyric acid were studied in the temperature interval from 5.7 to 300 K using a vacuum adiabatic calorimeter. The curve C _p (T) in the mentioned temperature interval is S-shaped without any anomalies. Based on the smoothed values of heat capacity, the calorimetric entropy $ S_{m}^{0} (T) - S_{m}^{0} (0) $ and the difference in the enthalpies $ H_{m}^{0} (T) - H_{m}^{0} (0) $ were calculated and tabulated. At the standard temperature 298.15 K, these values are equal to 158.1 ± 0.3 J K^?1 mol^?1 and 23020 ± 50 J mol^?1, respectively. At temperatures from 5 to 10 K, the function C _p (T) was found to obey the Debye law C = AT ³. Contrary to what has been supposed previously, the empirical Parks–Huffman rule for estimating entropy in the homologous series was shown to be not valid for the series glycine–β-alanine–γ-aminobutyric acid.     

Kinetics and mechanism of oxidation of neutral α ‐amino acids by sodium N‐chloro‐p‐toluenesulfonamide in acid medium

Kinetics of oxidation of α ‐amino acids, glycine, valine, alanine, and phenylalanine, by sodium N‐chloro‐p‐toluenesulfonamide or chloramine‐T (CAT) has been investigated in HClO₄ medium at 30°C. The rate shows first‐order dependence on both CAT and amino acid concentrations and an inverse first‐order on [H⁺]. The variation of ionic strength and the addition of p‐toluenesulfonamide and Cl^? ion had no effect on the reaction rate. Decrease of dielectric constant of the medium by increasing the MeOH content decreased the rate. Rate studies in D₂O medium showed the inverse solvent‐isotope effect of k_D2O/k_H2O=0.50. Proton‐inventory studies were carried out using H₂O–D₂O mixtures. The activation parameters have been computed. The proposed mechanism and the derived rate law are consistent with the observed kinetic data. An isokinetic relationship is observed with β=323 K, indicating enthalpy as a controlling factor. The rate of oxidation increases in the following order: Gly < Val < Phe < Ala. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 49–55, 2002     

Stopped-flow kinetic analysis of the oxidation of semicarbazide by hexachloroiridate(IV)

A kinetic analysis of the oxidation of semicarbazide (SEM) by the single-electron oxidant [IrCl₆]^2? has been carried out by stopped-flow spectrometric techniques. The reaction proved to be first order each in [IrCl₆ ^2?] and [SEM]_tot, leading to overall second-order kinetics. The variation in the observed second-order rate constant k′ with pH was explored over the pH range of 0–7.11. Spectrophotometric titration revealed a stoichiometry of Δ[IrCl₆ ^2?]/Δ[SEM]_tot = 4:1 for the redox reaction. On the basis of the rate law, the redox stoichiometry, and the rapid scan spectra, a reaction mechanism is proposed which involves parallel attacks of [IrCl₆]^2? on both H₂NCONHNH₃ ⁺ and H₂NCONHNH₂ as rate-determining steps, followed by several rapid reactions. The rate expression, derived from the reaction mechanism, was utilized to simulate the k′–pH profile yielding a virtually perfect fit and indicating that the reaction path involving H₂NCONHNH₃ ⁺ does not make a significant contribution to the overall rate. The reaction between [IrCl₆]^2? and H₂NCONHNH₂ was further studied as a function of both temperature and ionic strength. From the temperature dependence, activation parameters were obtained as: ?H ₂ ^?  = 34.9 ± 1.5 kJ mol^?1 and ?S ₂ ^?  = ?78 ± 5 J K^?1 mol^?1. The observed ionic strength dependence suggests that the rate-determining step is between [IrCl₆]^2? and a neutral species of SEM. Hence, both the temperature and ionic strength dependency studies are in good agreement with the proposed reaction mechanism, in which the rate-determining step involves an outer sphere electron transfer.     

Oxygen promoted radical polymerization of acrylonitrile in aqueous nitric acid. A kinetic study

The polymerization of acrylonitrile (AN) initiated by oxygen-ascorbic acid (AA)-ferric ion system was studied in dil. HNO₃ at 40°. The rate of polymerization, R_p, was found gravimetrically. In the [Fe³⁺] range, (2–5 × 10^?5 M, R_p was proportional to [AN]^{1.5 ± 0.05}, [O₂]^{0.5 ± 0.02} [AA]⁰ and [Fe³⁺]⁰; for [Fe³⁺] = (5–30) × 10^?5 M, it was proportional to [AN]^{1.8 ± 0.05}, [O₂]^{0.6 ± 0.02}, [AA]⁰ and [Fe³⁺]^{?0.9 ± 0.05}. A plausible reaction scheme is proposed and rate law presented to explain these results. R_p increased with ionic strength and [HNO₃] (up to ～0.25 M). An initial rate increase with temperature followed by a decrease was noticed. Chain lengths of the polymers were determined viscometrically.     

Oxidation of isoniazid by N‐haloarenesulfonamidates in alkaline medium: A kinetic and mechanistic study

The kinetics of oxidation of Isoniazid (INH) by sodium N‐haloarenesulfonamidates, chloramine‐T (CAT), bromamine‐T (BAT), chloramine‐B (CAB), and bromamine‐B (BAB), has been studied in alkaline medium at 303 K. The oxidation reaction follows identical kinetics with a first‐order dependence on each [oxidant] and [INH] and an inverse fractional‐order on [OH^−:]. Addition of the reaction product (p‐toluenesulfonamide or benzenesulfonamide) had no significant effect on the reaction rate. Variation of ionic strength and addition of halide ions have no influence on the rate. There is a negative effect of dielectric constant of the solvent. Studies of solvent isotope effects using D₂O showed a retardation of rate in the heavier medium. The reaction was studied at different temperatures, and activation parameters have been computed from the Arrhenius and Eyring plots. Isonicotinic acid was identified as the oxidation product by GC‐MS. A two‐pathway mechanism is pro‐posed in which RNHX and the anion RNX⁻ interact with the substrate in the rate‐limiting steps. The mechanism proposed and the derived rate laws are consistent with the observed kinetics. The rate of oxidation of INH increases in the order: BAT > BAB > CAT > CAB. This effect is mainly due to electronic factors. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 221–230, 2000     

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.     

Effects of Solvent Composition and Temperature on K+–18-Crown-6 Complexation in Acetonitrile–Water Mixed Solvents

Complexation of K⁺ by 18-crown-6 ether (18C6) in pure water and in acetonitrile–water mixed solvents containing 0.1 mol-dm^{? 3} (C₂H₅)₄NCl has been systematically studied by isothermal titration calorimetry (ITC) at 293, 298, and 303 K. The formation constant K of the 1:1 [K(18C6)]⁺ complex and the complexation enthalpy Δ _rH were simultaneously determined from the titration data. The logK and Δ _rH(kJ-mol^{? 1}) values at 298 K are 2.04, ?26.2 in pure water and 2.23, ?25.0; 2.61, ?24.2; 2.95, ?23.8; 3.48, ?21.0; 3.85, ?19.4; 4.36, ?18.7; and 5.73, ?17.0 in the mixed solvents at x _AN (mole fraction of acetonitrile) of 0.043, 0.135, 0.258, 0.448, 0.578, 0.759, and 1.0, respectively. The change in heat capacity for the complex formation, Δ C _p °, was also determined by the temperature dependence of Δ _rH. Whereas the Δ C _p ° is (57 ± 11) and (63 ± 20) J-mol^{? 1}-K^{? 1} in pure water and in the solvent mixture at x _AN = 0.043, respectively, it decreases with increasing x _AN. The Δ C _p ° values are ?(48 ± 11), ?(110 ± 25), ?(354 ± 40), ?(359 ± 24), and ?(304 ± 30) J-mol^{? 1}-K^{? 1} at x _AN = 0.135, 0.258, 0.448, 0.578, and 0.759, respectively. The changes in complexation thermodynamics (Δ Δ _rG, Δ Δ_rH, and Δ Δ _r S) are discussed in terms of the corresponding transfer thermodynamics of K⁺, 18-crown-6, and [K(18C6)]⁺ upon transferring from water to acetonitrile–water mixed solvents. It was found that hydrophobic solvation of the complex [K(18C6)]⁺ plays an important role in complex formation occurring in water and in the water-rich mixed solvent. Moreover, changes in solvent structure significantly affect the transfer enthalpy and entropy of each species, i.e., K⁺, 18-crown-6, and [K(18C6)]⁺. The observed monotonous changes in the complexation Gibbs energy, enthalpy, and entropy with solvent composition are due to the effective compensation of the Δ _trG, Δ _trH, and Δ _tr S for K⁺ with those for 18-crown-6 and [K(18C6)]⁺.     

High-Pressure Solubility of l-Methionine in Water

The solubility (m _S) of l-methionine in water was measured at 298.2 K and pressures up to 200 MPa. The data were fitted to the equation ln(m _S/mol·kg^?1) = ?4.62 × 10^?6 (p/MPa)² + 2.65 × 10^?3 (p/MPa) ? 0.970 with a standard deviation of σ(ln m _S) = 0.002. The pressure coefficient of the logarithm of solubility (?ln m _S/?p) _T was thermodynamically estimated to be (2.62 ± 0.34) × 10^?3 MPa^?1 at 0.10 MPa using several parameters such as partial molar volume and activity coefficient of l-methionine in water and molar volume of solid l-methionine. The resulting value agrees well with the second term on the right-hand side of the fitted equation above, indicating the reliability of the high-pressure solubility measurements. The value of (?ln m _S/?p) _T also was compared with those of other amino acids.     

Kinetic studies on H+-catalyzed aquation and hydrogen peroxide oxidation of tris-asparaginatochromium(III)

Tris-asparaginatochromium(III), [Cr(Asn)₃]⁰ (where Asn forms a 5-membered chelate ring via amine nitrogen and α-carboxylate oxygen atoms) and its mono- and diaqua-derivatives were obtained, and their acid-catalyzed aquation was studied. The first reaction for [Cr(Asn)₃]⁰ and [Cr(Asn)₂(H₂O)₂]⁺ is the chelate ring opening at the Cr-NH₂ bond, leading to metastable intermediates. Kinetics of these processes were studied spectrophotometrically in 0.1–1.0 M HClO₄ at 303 and 333 K, respectively. A linear dependence of k _obs on [H⁺], k _obs = a + b[H⁺] was determined for both the complexes. Additionally, oxidation of chromium(III) to chromate(VI) by hydrogen peroxide was studied. The process proceeds through a chromium(V) intermediate, which is next transformed, in faster parallel steps into CrO₄ ^2? and [Cr(O₂)₂]^3? anions. The latter species, a chromium(V)-peroxo complex, is metastable under a large excess of H₂O₂. Kinetics of oxidation of [Cr(Asn)₃]⁰ were studied at 298 K, at constant [OH^?], within 0.2–1.0 M H₂O₂ range. A linear dependence of k _obs on H₂O₂ was established. A mechanism is proposed, where the rate-determining step is an inner sphere 2-electron transfer within a precursor chromium(III) complex with coordinated O₂H^? anion of the [Cr(Asn)₂(OH)(HO₂)]^? formula. EPR results provided clear evidence for formation of a relatively stable tetrakis(η ²-peroxo)chromate(V) complex, [Cr(O₂)₄]^3?.