Experimental Rate Law Research Articles

Degradation of indigo carmine dye with peroxydisulphate ion in aqueous sulphuric acid phase: Kinetic study

AbstractThe quest for cleaner environments is a global concern. Hence, the investigation of degradation of the indigo carmine dye (IC) with peroxydisulphate ion in an aqueous sulphuric acid system with a view to understanding its kinetic degradation and mechanism. The degradation depicts first‐order kinetics in [S2O82−] and [IC], and the degradation mole ratio of IC: S2O82− is 1:1. The degradation rate is dependent on the change in ionic strength and medium permittivity of the system. Also, added ions (NH4+ and NO3−) influence the degradation rate of the dye which further supported the outcome of the change in ionic strength. Free radical participation is ruled out. The experimental rate law is given as (Kk3[H+])[IC][S2O82−]. Owing to the absence of detectable intermediates in the degradation process, an outer‐sphere mechanism is proposed. The study is significant in textile industries and medical settings for making environments less toxic with a well‐understood degradation rate pathway.

A Kinetic Study of Oxidation of New [Co(L)2(H2O)2] Complex by N-bromosuccinimide (NBS)

The kinetics of the oxidation of the [Co(L)2(H2O)2] complex by N-bromosuccinimide (NBS) in aqueous media (L = bidentate ligand mono deprotonated anion derived from methyl salicylaldehyde and sulfacetamide) were investigated over a pH range of 4.2–5.4, temperatures ranging from 25°C to 40°C, and an ionic strength of 0.1 mol/l–0.4 mol/l for both NBS and complex concentrations. The reaction rate over the studied pH ranges was predicted to be first order NBS and complex dependent and to rise with decreasing [H+]. It was compatible with the experimental rate law to say that a process in which the complex’s dehydrogenated form is greater reactivity compared to its conjugate acid. Acrylonitrile polymerisation was tested for its abundance of free radicals in the reaction admixture. It was supposed that transfer of electrons and formation of initial cobalt(III) products, which were eventually were tardily transformed into the final cobalt(III) products, occurred by an inner-sphere mechanism.

Phenoxythiazoline (FTz)‐Cobalt(II) Precatalysts Enable C(sp2)–C(sp3) Bond‐Formation for Key Intermediates in the Synthesis of Toll‐like Receptor 7/8 Antagonists**

AbstractEvaluation of the relative rates of the cobalt‐catalyzed C(sp2)–C(sp3) Suzuki–Miyaura cross‐coupling between the neopentylglycol ester of 4‐fluorophenylboronic acid and N‐Boc‐4‐bromopiperidine established that smaller N‐alkyl substituents on the phenoxyimine (FI) supporting ligand accelerated the overall rate of the reaction. This trend inspired the design of optimal cobalt catalysts with phenoxyoxazoline (FOx) and phenoxythiazoline (FTz) ligands. An air‐stable cobalt(II) precatalyst, (FTz)CoBr(py)3 was synthesized and applied to the cross‐coupling of an indole‐5‐boronic ester nucleophile with a piperidine‐4‐bromide electrophile that is relevant to the synthesis of reported toll‐like receptor (TLR) 7/8 antagonist molecules including afimetoran. Addition of excess KOMe⋅B(OiPr)3 improved catalyst lifetime due to attenuation of alkoxide basicity that otherwise resulted in demetallation of the FI chelate. A first‐order dependence on the cobalt precatalyst and a saturation regime in nucleophile were observed, supporting turnover‐limiting transmetalation and the origin of the observed trends in N‐imine substitution.

Mechanistic Investigations of Phenoxyimine-Cobalt(II)-Catalyzed C(sp2)-C(sp3) Suzuki-Miyaura Cross-Coupling.

The mechanism of phenoxyimine (FI)-cobalt-catalyzed C(sp2)-C(sp3) Suzuki-Miyaura cross-coupling was studied using a combination of kinetic measurements and catalytic and stoichiometric experiments. A series of dimeric (FI)cobalt(II) bromide complexes, [(4-CF3PhFI)CoBr]2, [(4-OMePhFI)CoBr]2, and [(2,6-diiPrPhFI)CoBr]2, were isolated and characterized by 1H and 19F NMR spectroscopies, solution and solid-state magnetic susceptibility, electron paramagnetic resonance (EPR) spectroscopy, X-ray crystallography, and diffusion-ordered NMR spectroscopy (DOSY). One complex, [(4-CF3PhFI)CoBr]2, was explored as a single-component precatalyst for C(sp2)-C(sp3) Suzuki-Miyaura cross-coupling. Addition of potassium methoxide to [(4-CF3PhFI)CoBr]2 generated the corresponding (FI)cobalt(II) methoxide complex as determined by 1H and 19F NMR and EPR spectroscopies. These spectroscopic signatures were used to identify this compound as the resting state during catalytic C(sp2)-C(sp3) coupling. Variable time normalization analysis (VTNA) of in situ catalytic 19F NMR spectroscopic data was used to establish an experimental rate law that was first-order in a (FI)cobalt(II) precatalyst, zeroth-order in the alkyl halide, and first-order in an activated potassium methoxide-aryl boronate complex. These findings are consistent with turnover-limiting transmetalation that occurs prior to activation of the alkyl bromide electrophile. The involvement of boronate intermediates in transmetalation was corroborated by Hammett studies of electronically differentiated aryl boronic esters. Together, a cobalt(II)/cobalt(III) catalytic cycle was proposed that proceeds through a "boronate"-type mechanism.

Use of Cu(II) catalyst assisted oxidative decolorization of dye by chlorinating species in water: A kinetic and mechanistic study with acid red1 dye

A quick and easy decolorization method has been created in the current study to get rid of the Acid Red 1 (AR1) dye from the wastewater. At 298 K, the kinetics of oxidative decolorization of AR1 dye with Chloramine-B (CAB) in NaOH medium, catalyzed by copper(II) sulphate, have been examined spectrophotometrically (λmax = 506nm). The experimental rate laws found are as follows: d[CAB]/dt = k [CAB]0 [AR1]0 [Cu(II)]x / [OH−]y in an alkaline medium, where x and y are less than unity.Under ideal experimental conditions, 90% dye decolorization is achieved in 30 minutes using concentrations of 0.003M [CAB], 0.0003M [AR1], 0.003M [Cu(II), and 0.003M [OH−].In the current kinetic redox system, the Cu(II) catalyst showed to be an effective homogeneous catalyst. The 4-acetamido-5,6-dioxo-5,6-dihydro naphthalene-2-sulphonic acid is identified as the oxidation product using mass spectrum analysis. The FTIR spectra show the absence of N=N stretching bands at 1489 cm−1 which confirms the oxidative breakdown of the azo group, a fundamental chromophore responsible for color, which induces toxicity in the waste water. The decolorization reaction catalyzed by Cu(II) is approximately six times faster than the uncatalyzed reaction. The catalytic constant (Kc) is calculated at various temperatures, and activation parameters for copper(II) are also evaluated. The observed results are explained by plausible mechanisms, and relative rate laws has been deduced. Chemical oxygen demand (COD) has been significantly reduced by the oxidative decolorization process. Phytotoxicity tests revealed that the treated dye sample is less toxic than the untreated dye sample. An economic analysis is carried out. Notably, with appropriate modifications, the developed oxidative decolorization technique is expected to benefit in the removal of AR1 dye present from industrial wastewater.

Kinetic studies on the persulfate oxidation of methylene blue in the absence and presence of silver(I) as a catalyst in aqueous and micellar media

AbstractThe kinetics and mechanism of the oxidative decolorization of methylene blue (MB+) as a cationic dye by persulfate using silver(I) catalyst in aqueous acidic medium were studied. The effects of different parameters like [H+], [Ag+], reactant concentration, micelles, and temperatures were investigated. The kinetic data showed that the oxidative decolorization of [MB]+ by persulfate obeyed pseudo‐first‐order kinetics by taking a large excess of [S2O82−] over [MB+]. The observed rate constant increases with increasing of [H+]. A plausible mechanism for the silver(I) enhanced decolorization of [MB]+ by persulfate is suggested which is consistent with the experimental rate law. The effect of micelles such as SDS and Triton X‐100 on the reaction rate is investigated. The rate of reaction decreases with increasing [SDS] but is not affected by Triton X‐100. The mechanism of the electron transfer process between [MB]+ and S2O82– proceeds through an outer‐sphere mechanism. Thermodynamic activation parameters ΔH* and ΔS* were calculated. The experimental data may be useful for the layout of wastewater treatment containing various types of dyes.

Chemistry students’ conceptual difficulties and problem solving behavior in chemical kinetics, as a component of an introductory physical chemistry course

Abstract The identification of undergraduate chemistry students’ conceptual difficulties and common mistakes with basic concepts and problems in chemical kinetics provided the aim for this study, which involved 2nd-year/4th semester students who had passed the chemical kinetics component of a physical chemistry course. The study involved the analysis, evaluation and interpretation of students’ answers to the final examination in chemical kinetics. Three achievement groups, for the various topics, were identified: Group A, high achievement (mean ≈ 85%): (a) the steps in a chain-reaction mechanism, (b) integrated 1st- and 2nd-order rate laws; and (c) the Lindemann–Hinshelwood mechanism. Group B, intermediate achievement (mean ≈ 74%): (a) half-life, (b) instantaneous rate and the extent of reaction variable (ξ), (c) the Michaelis–Menten mechanism, and (d) theoretical rate law not asking for a final formula. Group C, low achievement (mean ≈ 54%): (a) experimental rate law and the reaction rate constant on the basis of an experimental-data table, (b) extracting the theoretical rate law, and (c) the Arrhenius equation. Students’ errors and misconceptions have also been identified. Successful students tended to respond well to straightforward questions on the theory of the subject, but had difficulties when solving problems. It is essential that teachers understand the potential of their students, especially possible misconceptions they may hold, and the teaching approaches that may contribute to overcoming the student difficulties. Problems in chemical kinetics can be very demanding both in terms of algebraic manipulations and conceptually. Teaching should focus on problem solving, with the emphasis on students themselves trying to solve the problems.

Oxidation of hexacyanoferrate(II) ion by hydrogen peroxide: evidence of free radical intermediacy

The redox reaction between hexacyanoferrate(II) ion as the reducing agent and hydrogen peroxide as the oxidizing one, in slightly acid (pH 4.36–6.65) aqueous solutions containing phosphate ions, has been studied by means of an UV–Vis spectrophotometer monitoring the formation of Fe(III) at 420 nm. The initial hydrolysis of the Fe(II)-cyanide complex reactant to yield a pentacyanoaquaferrate(II) intermediate, as well as a decrease in the solution pH (acid catalysis), had both a positive effect on the reaction rate, whereas an increase in the concentrations of Fe(III), phosphate and chloride ions, and d-mannitol had a negative effect (inhibition). A computer program, specifically designed for this purpose, allowed arriving at a complex eight-coefficient experimental rate law by application of the initial rate method, accounting for the dependences of the reaction rate on the concentrations of Fe(II), H2O2 and Fe(III). The reaction was characterized by a low value of the apparent activation energy (28.9 ± 2.7 kJ mol−1). Finally, a multi-step reaction mechanism, involving the participation of a penta-coordinated Fe(II) complex, and hydroxyl, superoxide and other free radicals as intermediates, has been proposed. This mechanism was supported by the available experimental information and confirmed by numerical simulations performed via the fourth order Runge–Kutta integration method.

Kinetics and mechanism of the reduction of n-(2-hydroxyethyl)ethylenediaminetriacetatoiron(III) complex by thioglycol in bicarbonate buffer medium

The kinetics and mechanism of reduction of N-(2-hydroxyethyl) ethylenediaminetriacetatoiron (III) complex (hereafter [Fe(III)HEDTAOH2]) by thioglycol (hereafter RSH) has been studied spectrophotometrically in a bicarbonate buffer medium. The study was carried out under pseudo-first order conditions of an excess of thioglycol concentration at 28 ± 1℃, I = 0.44 mol dm-3 (KNO3) and λmax = 490 nm. The reaction is first order in [Fe(III)HEDTAOH2] and half order in [RSH] and a stoichiometric mole ratio of [Fe(III)HEDTAOH2]: RSH is 2:1. Reaction rates increased with increase in ionic strength (I) and dielectric constant (D) of the reaction medium of the reaction. The reaction displayed positive primary salt effect, which suggests the composition of activated complex are likely charged reactants ions. Test for possibility of an intermediate complex formation shows negative as Michaelis-Menten plot was linear with very negligible intercept. Based on the findings, outer-sphere mechanism is proposed for the reaction. The experimental rate law obtained is; - = k2 [Fe(III)HEDTAOH2][RSH]½  Â

Kinetics and Mechanism of Oxidative Conversion of Methionine to Sulfone by Chloramine-B in Acid Medium

Background: Methionine, Met, is one of the sulfur containing amino acids required in the human body by certain biochemical reactions. Since Met is not biosynthesized in humans, it needs to be supplied externally in diet. Met is highly susceptible to oxidation. Objective: The oxidation of Met to its sulfone by CAB in aqueous perchloric acid medium at 323 K has been kinetically studied. Method: Effect of varying ionic strength, solvent composition, dielectric constant has been determined. Effect of reduction product of Chloramine-B (CAB), benzenesulfonamide, on the reaction rate has also been investigated. Conclusion: The experimental rate law obtained is: rate = k׀ [CAB] [H2O]. Activation parameters have been evaluated using Arrhenius and Eyring plots. A mechanism consistent with the observed kinetic data has been discussed. A rate law has been derived based on the mechanism. Keywords: Chloramine-B, kinetics, mechanism, methionine, oxidation, rate law, reduction, sulfone.

Behavior of IrCl3 as a Homogeneous Catalyst on the Oxidation of N-Acetylglucosamine in Acid Medium and Uncatalyzed Reaction in Alkaline Medium with Bromamine-B: Exploration of Kinetic, Mechanistic and Catalytic Chemistry

The experimental rate laws for the oxidation of N-acetylglucosamine with bromamine- B are: − d[BAB]/dt = k/ [BAB]1 [GlcNAc]0.69 [HClO4]−0.76 [IrCl3]0.48 [BSA]−0.33 in acid medium and –d[BAB]/dt = k/ [BAB]1 [GlcNAc]1 [NaOH]0.79 in alkaline medium. The IrCl3 catalyzed reaction is thirteen fold faster than uncatalyzed reaction. Appropriate mechanisms and rate laws were deduced. The reaction of N-acetylglucosamine with Bromamine-B in acid and alkaline medium is

Palladium(II) Catalyzed Oxidation of Glycine by Ferricyanide in Acid Medium: Kinetics and Mechanism

Glycine (Gly) is one of the amino acids, commonly found in proteins, coded by codons GGU, GGC, GGA and GGG. Glycine is the unique non-optically active amino acid. The Gly-ferricyanide reaction catalyzed by Pd(II), under pseudo-first-order conditions, has been spectrophotometrically monitored at the ferricyanide λmax of 303 nm at constant temperature. The experimental rate law for the reaction is: rate = kı [Fe(CN)6 3-] [Gly]x [H+]y [Pd(II)]z, where x, y and z are fractional orders. Additionally, the effect on the rate of adding the reduction product, [Fe(CN)6 4-], has been found to be negligible. Variations of the ionic strength and the dielectric constant of the reaction medium have an effect on the rate. Activation parameters have been evaluated using Arrhenius and Eyring plots. A suitable mechanism has been presented and the derived rate law is consistent with the kinetic data. Keywords: Acid medium, activation parameters, ferricyanide, glycine, mechanism, oxidation kinetics, palladium(II) catalysis, rate law.

Inhibition of Aquated Sulfur Dioxide Autoxidation by Aliphatic, Acyclic, Aromatic, and Heterocyclic Volatile Organic Compounds

ABSTRACTThe oxidation of dissolved sulfur dioxide, sulfur(IV), by oxygen proceeds through the involvement of sulfoxy radicals among which sulfate radical anion is the main chain carrier. When organics are present, they inhibit the oxidation of sulfur(IV) via scavenging of SO4− radicals. In contrast to previous studies, which were limited mostly to aliphatic compounds, this paper presents the results of the effect of 13 new volatile organic compounds (VOCs) including aromatic and heterocyclic on uncatalyzed sulfur(IV) autoxidation at pH 8.2 and 25°C. In all cases, the kinetics was first order in the presence and absence of VOCs and experimental rate law was Eq. (1). urn:x-wiley:05388066:media:kin21069:kin21069-math-0001where −d[S(IV)]/dt is the rate of sulfur(IV) disappearance, kobs is the first‐order rate constant in the presence of inhibitor, ko is the first‐order rate constant in the absence of inhibitor, [S(IV)] is concentration of sulfur(IV) at time, t, and B is an inhibition parameter.VOCs cause inhibition by scavenging sulfate radical anions, which propagate the autoxidation chain. An analysis of B (Eq. (1)) and kinh (Eq. (2)) values for 21 aliphatic, aromatic, acyclic, and heterocyclic organic compounds showed that these to be related by Eq. (3) for a subgroup and Eq. (4) for b subgroup. urn:x-wiley:05388066:media:kin21069:kin21069-math-0002a subgroup (benzamide, 2,2‐dimethyl‐1‐propanol, 1‐hexanol, methanol, ethanol, 1‐propanol, 2‐ propanol, 1‐butanol, 2‐butanol, ethylene glycol, rebaudioside A) urn:x-wiley:05388066:media:kin21069:kin21069-math-0003b subgroup (o‐toluic acid, m‐toluic acid, p‐toluic acid, 4‐hydroxybenzoic acid, 1‐heptanol, glycerol, sucralose, acesuifame K, glycine, 3‐pentanol) urn:x-wiley:05388066:media:kin21069:kin21069-math-0004

Partial oxidation of methane over Ni0/La2O3 bifunctional catalyst IV: Simulation of methane total oxidation, dry reforming and partial oxidation using the Quasi-Steady State Approximation

Simulations of methane total oxidation (TOM) at 873K on La2O3 and dry reforming (DRM) at 693K reactions over Ni0/LaO3 were calculated for low and high conversions of reactants, based on experimental power rate law equations described in a previous paper and classical kinetics. According to Boudart’s school approach of Classical Kinetics, kinetic rate equations of TOM and DRM reactions were then established based on the Quasi-Steady State Approximation (QSSA) theory. The concept of two-step sequences was used for TOM and DRM which occur in the indirect process of partial oxidation of methane (POM). The QSSA simulation of POM process was subsequently developed at 1053K and compared to the simulation of TOM, at the same temperature, to kinetically demonstrate that the TOM catalytic cycle is the rate determining cycle (rdc) of the POM process. Synthesis of a novel POM catalyst in the future can be based on the present model and conclusion, taking into account that the methane combustion reaction provides the rate determining catalytic cycle (rdc) of the overall POM process.

From Resting State to the Steady State: Mechanistic Studies of Ene-Yne Metathesis Promoted by the Hoveyda Complex.

The kinetics of intermolecular ene-yne metathesis (EYM) with the Hoveyda precatalyst (Ru1) has been studied. For 1-hexene metathesis with 2-benzoyloxy-3-butyne, the experimental rate law was determined to be first-order in 1-hexene (0.3-4 M), first-order in initial catalyst concentration, and zero-order for the terminal alkyne. At low catalyst concentrations (0.1 mM), the rate of precatalyst initiation was observed by UV-vis and the alkyne disappearance was observed by in situ FT-IR. Comparison of the rate of precatalyst initiation and the rate of EYM shows that a low, steady-state concentration of active catalyst is rapidly produced. Application of steady-state conditions to the carbene intermediates provided a rate treatment that fit the experimental rate law. Starting from a ruthenium alkylidene complex, competition between 2-isopropoxystyrene and 1-hexene gave a mixture of 2-isopropoxyarylidene and pentylidene species, which were trappable by the Buchner reaction. By varying the relative concentration of these alkenes, 2-isopropoxystyrene was found to be 80 times more effective than 1-hexene in production of their respective Ru complexes. Buchner-trapping of the initiation of Ru1 with excess 1-hexene after 50% loss of Ru1 gave 99% of the Buchner-trapping product derived from precatalyst Ru1. For the initiation process, this shows that there is an alkene-dependent loss of precatalyst Ru1, but this does not directly produce the active catalyst. A faster initiating precatalyst for alkene metathesis gave similar rates of EYM. Buchner-trapping of ene-yne metathesis failed to deliver any products derived from Buchner insertion, consistent with rapid decomposition of carbene intermediates under ene-yne conditions. An internal alkyne, 1,4-diacetoxy-2-butyne, was found to obey a different rate law. Finally, the second-order rate constant for ene-yne metathesis was compared to that previously determined by the Grubbs second-generation carbene complex: Ru1 was found to promote ene-yne metathesis 62 times faster at the same initial precatalyst concentration.

Oxidation of glycylglycine by ferricyanide in acid medium: Kinetics and mechanism

AbstractThe oxidative degradation of glycylglycine (GlyGly) to formic acid, ammonium ion, and carbon dioxide occurs when it reacts with ferricyanide in acid medium, which has been studied spectrophotometrically at 303 nm at constant temperature. Kinetic runs have been performed under a pseudo-first-order condition of [GlyGly]0 >> [ferricyanide]0. The experimental rate law obtained for the redox reaction is: rate = ki [Fe(CN)63-] [GlyGly]x [H+]y[Pd(II)]0, where x and y are fractional orders. Effects of ionic strength and dielectric constant are also investigated. Activation parameters have been evaluated using Arrhenius and Eyring plots. A probable mechanism has been proposed and the derived rate law is consistent with the kinetic data.

Synthesis and Reactivity of Oxorhenium(V) Methyl, Benzyl, and Phenyl Complexes with CO: Implications for a Unique Mechanism for Migratory Insertion

The complexes [(DAAm)Re(O)(R)] [DAAm = N,N-bis(2-arylaminoethyl)methylamine; aryl = C6F5], 1, R = Me; 3a–d (R = benzyl, a; 4-methylbenzyl, b; 4-fluorobenzyl, c; 4-methoxybenzyl, d); and 4, R = Ph, were synthesized. CO insertion into the Re–R bond in 1 and 3a–d resulted in the formation of the acetyl complex, 2, and the (aryl)acetyl complexes, 5a–d respectively. The formation of 5a–d proceeded at a faster rate (7 h) than the formation of 2 (72 h) under the same conditions. No reaction was observed however for the phenyl complex 4 with CO. Kinetics for CO insertion into the various Re–R bonds were examined, and the experimental rate law was determined to be Rate = kobs[Re][CO]. The activation parameters for CO insertion into 1 and 3a were determined to be ΔG⧧(298 K) = 24(1). The enthalpy of activation ΔH⧧ was determined to be 9(1) and 10(3) kcal/mol for 1 and 3a, respectively, and the entropy of activation, ΔS⧧, was −49(2) and −36(4) cal/mol·K. Computational studies (M06) are consistent with the hypothesis ...

Kinetics and mechanism of the formation of silver nanoparticles by reduction of silver (I) with maltose in the presence of some active surfactants in aqueous medium

The kinetics and mechanism of the formation of silver nanoparticles by reduction of Ag+ with maltose were studied spectrophotometrically by monitoring the absorbance change at 412 nm in aqueous and micellar media at a temperature range 45–60 °C. The reaction was carried out under pseudo-first-order conditions by taking the [maltose] (>tenfold) the [Ag+]. A mechanism of the reaction between silver ion and maltose is proposed, and the rate equation derived from the mechanism was consistent with the experimental rate law. The effect of surfactants, namely cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant), on the reaction rate has been studied. The enthalpy and the entropy of the activation were calculated using the transition state theory equation. The particle size of silver sols was characterized by transmission electron microscopy and some physiochemical and spectroscopic tools.

Kinetics and mechanism of periodate oxidation of ternary orotatochromium(iii) complexes bearing oxalate or malonate co-ligands

Oxidation kinetics of complexes [CrIII(OR)(HOX)(H2O)3]+ and [CrIII(OR)(HM)(H2O)3]+ (OR is orotic acid, HOX is oxalic acid, HM is malonic acid) by periodate in aqueous acidic medium was studied using spectrophotometric measurements in the pH range 3.34–4.63 at different temperatures. The reaction is first order in concentrations of both the IO4− ion and complex. For both complexes, the oxidation rate increases with the pH increase. The experimental rate law is consistent with a mechanism in which the deprotonated ([CrIII(OR)(OX)(H2O)2]) and protonated ([CrIII(OR)(HM)(H2O)3]+) species are significantly more reactive. Apparently, electron transfer proceeds through an inner sphere mechanism via coordination of the IO4− ion to chromium(iii). Thermodynamic activation parameters were calculated using the transition state theory equations.

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.