Non-isothermal Kinetics of the Thermal Decomposition of 3-Nitro-1,2,4-triazol-5-one Magnesium Complex

Introduction3 Nitro 1,2 ,4 triazol 5 one (NTO)metalcomplexeshavemanyspecialstructuresandsomepotentialusesinammunition .1 4 Wepreviouslypreparedanddeterminedthecrystalstructureofitsmagnesiumcomplex ,5andinthispaper ,wediscusseditsthermalbehaviorbyDSCandTG/DTGtechniquesandstudieditsnon isothermalkineticsbythemeansoftheKissingermethod ,theOzawamethod ,thedifferentialmethodandtheintegralmethod .ExperimentalSample[Mg(H2 O) 6 ](NTO) 2 ·2H2 Owaspreparedasfollows :AcalculatedamountofMg(OH…     

Kinetic study of thermal degradation of di-, chlorodi- and triorganotin(IV) complexes of 2-[(2,6-dichlorodiphenyl)amino]benzene acetate

The organotin complexes of the general formulae R₂SnL₂, R₂SnLCl and R₃SnL where R = C₄H₉, C₆H₅, and C₇H₇ and L = 2-[(2,6-dichlorodiphenyl)amino]benzene acetate, were subjected to thermal decomposition by thermogravimetric analysis (TGA). The decomposition of these compounds occurs mostly in two steps. Kinetic parameters such as order of reaction (n), activation energy (Ea), enthalpy (ΔH^?) and entropy (ΔS^?) of activation were calculated by using the Coats and Horowitz methods. The calculated values are in good agreement with observed TG values that confirm the structural integrity of the complexes.     

Kinetics of basic hydrolysis of tris(1,10‐phenanthroline)iron(II) in macromolecular assemblies of CTAB

The kinetics of basic hydrolysis of tris(1,10‐phenanthroline)iron(II) has been carried out in aqueous, N‐cetyl‐N,N,N‐trimethyl ammonium bromide (CTAB) micellar, and CTAB reverse micellar media by UV–visible spectroscopy system. The reaction follows the overall second‐order kinetics; first order in each Fe(II) complex and the base (^?OH). CTAB micelles catalyze the reaction rate through the adsorption of the Fe(II) complex and the hydroxyl ions on the micellar surface. In the reverse micellar medium, interesting physicochemical features are observed. Being ionic nature of reactants, both the reactants prefer to stay and react inside the water pool in place of the hydrophobic environment. The rate increases with w, that is, the size of the water pool, attains a maximum value at w = 8.33, and then decreases. But the rate increases as the concentration of surfactant increases at fixed w values. For a better explanation of the kinetic data, the activation parameters, standard enthalpy of activation (Δ^?H°), standard entropy of activation (Δ^?S°), and energy of activation (E_a) were determined. All kinetic data corroborate the proposed mechanism. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 579–589, 2011     

A Thermodynamic and Kinetic Insight into the Pathways Leading to a Highly Functionalized Ketenimine: A Computational Study

All steps of two mechanistic pathways for the synthesized ketenimine through a multicomponent reaction between cyclohexyl isocyanide 1 and acetylen ester 2 in the presence of CH‐acid 3 have been thermodynamically and kinetically evaluated. Intrinsic reaction coordinate calculations were performed for the optimized structures to verify the connectivity of all transition states with reactants and products. The kinetic data showed that the step 1 of the two proposed mechanisms was a rate‐determining step. Also, activation (ΔG^?, ΔH^?, ΔS^?) and thermodynamic (ΔG°, ΔH°, ΔS°) parameters confirmed that the second mechanism for generation product 4b was favored energetically. In addition, the single‐point ¹H and ¹³C NMR (GIAO) chemical shift calculations showed that the product obtained from the approval pathway was according to the experimental data.     

Thermochemical properties from G3MP2B3 calculations,Set‐2: Free radicals with special consideration of CH2CH?C•CH2, cyclo−•C5H5, •CH2OOH,HO?•CO,and HC(O)O•

After a set of 32 free radicals was presented (Int J Chem Kin 34, 550–560, 2002), an additional 60 free radicals (Set‐2) were studied and characterized by energy minimum structures, harmonic vibrational wave numbers ω_e, moments of inertia I_A, I_B, and I_C, heat capacities C^o_p(T), standard entropies S^o(T), thermal energy contents H^o(T) ? H^o(0), and standard enthalpies of formation Δ_fH^o(T) at the G3MP2B3 level of theory. Thermodynamic functions at T = 298.15 K are presented and compared with recent experimental values where these are available. The mean absolute deviation between calculated and experimental Δ_fH^o(298.15) values by the previous set of 32 radicals is 3.91 kJ mol^?1. For the sake of comparison, only 49 species out of the 60 radicals of Set‐2 are characterized by experimental enthalpies of formation, and the corresponding mean absolute deviation between calculated and experimental Δ_fH^o(298.15) values is 8.96 kJ mol^?1. This situation is cause for demand of more and also more accurate experimental values. In addition to the above properties, parent molecules of a large set of the respective radicals are calculated to obtain bond dissociation energies D^o(298.15). Radical stabilization owing to resonance is discussed using the complete sets of total atomic spin densities ρ as a support. In particular, a short review about recent developments of the first‐order Jahn–Teller radical c‐C₅H₅^? is presented. In addition, radicals with negative bond energies are described, such as ^?CH₂OOH where the reaction path to CH₂O + HO^? has been calculated, as well as radicals which have two different parent molecules, for example C?N? O^?. For the reaction HO^? + CO → H^? + CO₂, two reaction paths are characterized by a total of 14 stationary points where the intermediate radicals HO? ^?CO and HC(O)O^? are involved. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 661–686, 2004     

Kinetic and Equilibrium Studies of Chromium(III) Removal by Macroporous Ion Exchanger Amberlyst‐15 (H+)

Chromium(III) sorption on macroporous strong cation exchanger Amberlyst‐15 (H⁺) was studied as a function of time and temperature. The rate constant values for chromium(III) sorption were calculated both for film and particle diffusion processes. The temperature was found to have a positive effect on both the diffusional processes. From the rate constant values, the energy of activation was calculated using the well‐known Arrhenius equation. The high values of energy of activation confirmed the film diffusional nature of the process. Equilibrium data were explained with the help of Langmuir equation. Various thermodynamic parameters (ΔH^?, ΔS^? and ΔG^?) from chromium(III) exchange on the resin were calculated. The ΔG^? values were found to be negative while both the ΔH^? and ΔS^? were positive.     

Kinetics and Mechanism of the Exothermic First-stage Decomposition Reaction for 1,5-Dimethyl-2,6-bis(2,2,2-trinitroethyl)-glycoluril

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Thermodynamic activation parameters for viscous flow of dilute aqueous solutions of ethylenediamine,trimethylenediamine and N,N-dimethyltrimethylenediamine

The density and the viscosity data have been used to determine the thermodynamic activation parameters, free energies (ΔG ^?), enthalpies (ΔH ^?) and entropies (ΔS ^?), for viscous flow of the systems; water (W) + ethylenediamine (ED), W + trimethylenediamine (TMD) and W + N,N-dimethyltrimethylenediamine (DMTMD) in the temperature range of 303.15–323.15 K over the composition range of 0 ≤ X ₂ ≤ 0.45, where X ₂ is the mole fraction of diamines. On addition of diamines to water, ΔG ^?, ΔH ^? and ΔS ^? values increase sharply, pass through a maximum and then decline. The heights of maximum in the ΔG ^? versus X ₂ curve vary as, W + DMTMD > W + TMD > W + ED. For all systems, the excess properties, ΔG ^{? E} , ΔH ^{? E} and ΔS ^{? E} are positive. The observed increase in thermodynamic values may be due to combined effect of hydrophobic hydration of diamines and water–diamine interaction as a result of hydrophilic effect.     

Polymerization of pyridazine and pyridazinone derivatives. XIV. Effects of solvent,concentration, and temperature on radical copolymerizability of 3(2-methyl)6-methylpyridazinone with styrene

The free-radical copolymerizability of 3(2-methyl)6-methylpyridazinone (I) with styrene (St)(M₁) has been reinvestigated at varying reaction conditions (solvent, monomer concentration, and reaction temperature). The copolymerization rates in protic solvents were not proportional to the monomer concentration. The overall activation energies in protic solvents were much affected by the monomer concentration. The results might be ascribed to the viscosity effect on the termination reaction, because the protic solvent was found to interact with I through hydrogen bonding to form a 1:1 complex which changed the viscosity of the reaction mixture. The monomer reactivity ratios were strongly affected by the reaction conditions. This might be explained by taking account of the solvation to the carbonyl group of I in the transition state, because clear relationships were not obtained by plots of log 1/r₁ against the values of both vC?O and vC?C stretching frequencies of I, but the values of both ΔΔH?(?ΔH?₁₁ ? ΔH?₁₂) and ΔΔS?(?ΔS?₁₁ ? ΔS?₁₂) decreased linearly with a decrease of the monomer concentration in order of benzene ～ dimethylformamide < ethanol < phenol < acetic acid systems.     

Possible tests for the mechanisms of ligand exchange in solids: The deaquation-anation of [Cr(NH3)5(H2O)]X3 salts

The possibility of using correlations of ΔH⁺ and ΔH, and of ΔH⁺ and ΔS⁺ to gain insight into the mechanisms of ligand-exchange reactions in solids are discussed. These correlations are tested using literature values for the deaquation-anation reactions of [Cr(NH₃)₅(H₂O)]X₃, where X^? = Cl^?, Br^?, I^? or NO^?₃. The poor agreement in the activation parameters reported in the literature precluded a meaningful test of the ΔH?ΔH^* correlation. This poor agreement suggests that these activation parameters are strongly influenced by experimental factors that have not been controlled in studies to date. nevertheless, there is a linear correlation of ΔH² and ΔS² which gives an isokinetic temperature of 367 ± 11 K. This isokinetic behavior suggests that the same mechanism is operative throughout the series.     

Mode Selective Stereomutation and Parity Violation in Disulfane Isotopomers H2S2, D2S2, T2S2

We report quantitative calculations of stereomutation tunneling in the disulfane isotopomers H₂S₂, D₂S₂, and T₂S₂, which are chiral in their equilibrium geometry. The quasi‐adiabatic channel, quasi‐harmonic reaction path Hamiltonian approach used here treats stereomutation including all internal degrees of freedom. The torsional motion is handled as an anharmonic reaction coordinate in detail, whereas all the remaining degrees of freedom are taken into account approximately. We predict how stereomutation is catalyzed or inhibited by excitation of the various vibrational modes. The agreement of our theoretical results with spectroscopic data from the literature on H₂S₂ and D₂S₂ is excellent. We furthermore predict the influence of parity violation on stereomutation as characterized approximately by the ratio (ΔE_pv/ΔE_±) of the (local or vibrationally averaged) parity violating potential ΔE_pv and the tunneling splittings ΔE_± in the symmetrical case. This ratio is exceedingly small for the reference molecules H₂O₂ and D₂O₂, and still very small (2⋅10⁻⁶ cm⁻¹) for H₂S₂, which, thus, all exhibit essentially parity conservation in the dynamics. However, for D₂S₂ it is ca. 0.002, and for T₂S₂ it is ca. 1, which seems to be the first case where such intermediate mixing through parity violation is quantitatively predicted for spectroscopically accessible molecules. The consequences for the spectroscopic detection of molecular parity violation are discussed briefly also in relation to other molecules.     

Kinetics of Stripping Ni(II) from the Ni‐BTMPPA Complex/BTMPPA/Kerosene System by Sulfate‐Acetato Solution

The kinetics of stripping of Ni²⁺ from a Ni‐BTMPPA complex, dissolved in a kerosene solution of BTMPPA (H₂A₂, Cyanex 272), by acidic sulfate‐acetato solution, was studied using the single (falling) drop technique and flux (F) method of data treatment. The empirical flux equation at 303 K is F_b (kmol/m²s) = 10^?4.35 [Ni²⁺] (1+10^?3.42 [H⁺]^?1)^?1 ([H₂A₂]_(o)^0.5+2.50 [H₂A₂]_(o))^?1 (1+6[SO₄^2?]) (1+3.20 [Ac^?]). Activation energy (E_a), entropy change in activation (ΔS^±), and enthalpy change in activation (ΔH^±) were measured under different experimental conditions. Based on the empirical flux equation, E_a and ΔS^±, the mechanism of Ni²⁺ stripping is provided. In a low [H⁺] region, the stripping reaction steps appear as [NiA⁺] → Ni²⁺ + A^? and [Ni(HA₂)₂]_(int) → [NiHA₂]⁺_(int) + HA_2(int)^? in lower and higher concentration regions of free BTMPPA, respectively, provided [SO₄^2?] and [Ac^?] are kept low. However, at higher [H⁺] concentrations, the stripping is under diffusion control. With increasing [SO₄^2?] and [Ac^?], the enhancement of the rate is attributed to the attack of the Ni(II) complex by SO₄^2? or HSO₄^? and Ac^? to form NiSO₄ or NiHSO₄⁺ and NiAc⁺ complexes. Negative ΔS^± values indicate that the rate‐determining stripping reaction steps occur via an substitution nucleophilic, bimolecular (S_N2) mechanism.     

Oxidation of Antitubercular Drug Isoniazid by a Lipopathic Oxidant,Cetyltrimethylammonium Dichromate: A Mechanistic Study

The oxidation of an antitubercular drug isoniazid by a lipopathic oxidant cetyltrimethylammonium dichromate (CTADC) in a nonpolar medium generates isonicotinic acid both in the presence and the absence of acetic acid. The conventional UV–vis spectrophotometric method is used to study the reaction kinetics. The occurrence of the Michaelis–Menten–type kinetics with respect to isoniazid confirms the binding of oxidant and substrate to form a complex before the rate‐determining step. The existence of the inverse solvent kinetic isotope effect, k(H₂O)/ k(D₂O) = 0.7, in an acid‐catalyzed reaction proposes a multistep reaction mechanism. A decrease in the rate constant with an increase in [CTADC] reveals the formation of reverse micellar–type aggregates of CTADC in nonpolar solvents. In the presence of different ionic and nonionic surfactants, CTADC forms mixed aggregates and controls the reaction due to the charge on the interface and also due to partition of oxidant and substrate in two different domains. High negative entropy of activation (ΔS^? = –145 and –159 J K^?1 mol^?1 in the absence and presence of acetic acid) proposes a more ordered and highly solvated transition state than the reactants. Furthermore, the solvent polarity‐reactivity relationship reveals (i) the presence of less polar and less ionic transition state compared to the reactants during the oxidation, (ii) differential contribution from nonpolar and dipolar aprotic solvents toward the reaction process, and (iii) the existence of polarity/hydrophobic switch at log P = 0.73. A suitable mechanism has been proposed on the basis of experimental results. These results may provide insight into the mechanism of isoniazid oxidation in hydrophobic environment and may assist in understanding the drug resistance in different location.     

Stationary points on the potential energy surface of O2−HF and O2−H2O

The determination of minima and saddle points on the potential energy surfaces of the hydrogen bonded species O₂^?HF and O₂^?H₂O is performed with unrestricted Hartree-Fock calculations. Geometries, electron density distributions, and relative energies for every stationary point are reported. Only one true minimum is found for O₂^?HF and for O₂^?H₂O, and this approximately corresponds to a structure where the partially positive hydrogen atom is located along one of the superoxide ion electron lone-pair directions. Calculated ΔH, ΔS, and ΔG values for the reaction between O₂^? and H₂O are in good agreement with experimental data.     

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Amino acids have been used as catalysts for the study of kinetic of enolisation of m-Methylacetophenone, in which iodination has been the chosen method. Several parameters like effect of ketone concentration, effect of dielectric constant, effect of catalysts etc. have been investigated for their effect on enolisation kinetics. The study is focused on β-alanine, dl-alanine, l-alanine and Glycine for their effects on the rate. The order of the rate constants obtained has been found to be in the order of increasing dipole moments of the amino acids i.e. l-alanine < Glycine < dl-alanine < β-alanine. With an increase in the temperature from 323 K to 338 K, an increase in the rate was from 1.3 to 2.12 mol^?1 min^?1. The ongoing reaction was found to be bimolecular in nature. The values of different thermodynamic parameters like Entropy (ΔS^≠), Enthalpy (ΔH^≠), Energy of activation (ΔEa) and Gibbs free energy (ΔF^≠) were found to be 6.20 e.u., 24.74 cal mol^?1, 25.20 k cal mol^?1 and 24.54 cal mol^?1 respectively.     

Heterolysis of H2 Across a Classical Lewis Pair, 2,6‐Lutidine⋅BCl3: Synthesis,Characterization, and Mechanism

We report that 2,6‐lutidine?trichloroborane (Lut?BCl₃) reacts with H₂ in toluene, bromobenzene, dichloromethane, and Lut solvents producing the neutral hydride, Lut?BHCl₂. The mechanism was modeled with density functional theory, and energies of stationary states were calculated at the G3(MP2)B3 level of theory. Lut?BCl₃ was calculated to react with H₂ and form the ion pair, [LutH⁺][HBCl₃^?], with a barrier of ΔH^≠=24.7 kcal mol^?1 (ΔG^≠=29.8 kcal mol^?1). Metathesis with a second molecule of Lut?BCl₃ produced Lut?BHCl₂ and [LutH⁺][BCl₄^?]. The overall reaction is exothermic by 6.0 kcal mol^?1 (Δ_rG°=?1.1). Alternate pathways were explored involving the borenium cation (LutBCl₂⁺) and the four‐membered boracycle [(CH₂{NC₅H₃Me})BCl₂]. Barriers for addition of H₂ across the Lut/LutBCl₂⁺ pair and the boracycle B?C bond are substantially higher (ΔG^≠=42.1 and 49.4 kcal mol^?1, respectively), such that these pathways are excluded. The barrier for addition of H₂ to the boracycle B?N bond is comparable (ΔH^≠=28.5 and ΔG^≠=32 kcal mol^?1). Conversion of the intermediate 2‐(BHCl₂CH₂)‐6‐Me(C₅H₃NH) to Lut?BHCl₂ may occur by intermolecular steps involving proton/hydride transfers to Lut/BCl₃. Intramolecular protodeboronation, which could form Lut?BHCl₂ directly, is prohibited by a high barrier (ΔH^≠=52, ΔG^≠=51 kcal mol^?1).     

Reaction rates for nucleophiles with cyanogen chloride: Comparison with two other digonal carbon compounds

The hydrolysis kinetics of CICN have been reinvestigated from pH 0.0–10.5 and from 18–40°C. In the pH range from 1–5, the hydrolysis rate is invariant and the activation parameters (ΔH? = 84 kJ mol^?1 and ΔS? = ?84 J mol^?1 K^?1) are consistent with water attack. In basic solution the rate is first order each in CICN and OH^? concentrations with parameters ΔH? and ΔS? equal to 82 kJ mol^?1 and + 54 J mol^?1 K^?1, respectively. The rate constants with 20 other donors have been measured. Nitrogen nucleophiles are more reactive than oxygen donors, and an alpha-effect is seen. The constants follow a pattern indicative of attack at carbon. Cyanate in its acid form reacts with nucleophiles. Further points on the cyanate rate–pH profile have been obtained. A chromate-catalyzed hydrolysis can contribute between pH 5–10. Some studies were made of the reaction of cyanate with hydrogen peroxide. Free energy correlations are presented.     

A Thermodynamic Study of Chromotropico-Titanium(III) Complex from Spectrophotometric Measurements

The formation of 1 : 2 titanium(III) complex with chromotropic acid (4, 5-dihydroxy-2, 7-naphthalene-disulfonic acid) was observed by spectrophotometric measurements at various ionic strengths. An expression, [Ti(III)]/D=1/Δ? + α_H²+/KΔ?[H₂R^2?]², was derived for the determination of the formation constant, K=7.2×10² liter² mol^?2 for the Ti(III).(HR)₂ ion in the pH range of 1.3–1.8 at constant ionic strength, I=0.2 M, at 25°C. The thermodynamic data for the reaction, Ti(III)+2H₃R^2?=Ti(III) (HR)₂+2H⁺, were calculated to be ΔG° = ?16 kJ mol^?1 ΔH° = 18 kJ mol^?1, ΔS° = 110 JK^?1 mol^?1, at 25°C.     

Study of the reaction of MoOS2(S2CNR2)2 with PPh3 in 1,2-dichloroethane: Part I. Kinetics of the teaction of MoOS2(S2CNR2)2 with triphenylphosphine PPh3

The kinetics of the reaction of MoOS₂(S₂CNR₂)₂ (R = CH₃, C₂H₅, n-C₃H₇) with PPh₃ have been studied using a Stopped-flow method. It was found that these MoOS₂(S₂CNR₂)₂ complexes react with PPh₃ in the form of an irreversible second-order reaction. The rate constants at 25°C are respectively 48.4, 23.8, and 20.8 mol^?1 dm³ s^?1 and the activation energies are 4.8, 4.9, and 5.0 Kcal/mol with R = CH₃, C₂H₅, and n-C₃H₇.     

Kinetics and Mechanism of the Exothermic First-stage Decomposition Reaction of Dinitroglycoluril

Introduction Dinitroglycoluril (DINGU) is a typical cyclourea nitramine. Its crystal density is 1.94 gcm-3. The detonation velocity corresponding to =1.94 gcm-3 is about 8450 ms-1. Its sensitivity to impact is better than that of cyclotrimethylenetrinitramine. It has the potential for possible use as high explosive from the point of view of the above-mentioned high performance. Its preparation,1-4 properties1-4 and hydrolytic behavior4 have been reported. In the present paper, we report i…