The influence of substituents on the kinetics of the reaction of carbonyl oxides with benzaldehyde

The reactivity of carbonyl oxides toward benzaldehyde was characterized by thek ₃₃/k ₃₃ ratio, wherek ₃₃ andk ₃₁ are the rate constants of the reactions of RCOO with PhCHO and diphenyldiazomethane Ph₂CN₂, respectively. Thek ₃₃/k ₃₁ ratios obtained at 60°C in acetonitrile range from 0.61·10⁻² (m-BrPh₂CN₂) to 20·10⁻² (Ph₂MeCHO). The reactions are probably preceded by the formation of a charge-transfer complex (CTC) with charge transfer from aldehyde to RCOO. The carbonyl oxide reacts with aldehydes by both the nucleophilic pathway (at the C atom of the—CHO group to form 1,2,4-trioxolane) and electrophilic pathway (by the attack at the aromatic ring with the intermediate formation of CTC). In the latter case, either 1,2,4-trioxolane or oxidation products of the phenyl ring are formed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 650–654, April, 2000.     

The Reactivity of Diphenyl Carbonyl Oxide in Reactions with Alcohols

The reactivities of ten alcohols in the reactions with diphenyl carbonyl oxide Ph₂COO is characterized by the ratio k ^OH ₃₃ /k ₃₁, where k ^OH ₃₃ and k ₃₁are the rate constants of Ph₂COO reactions with an alcohol and diphenyldiazomethane PH₂CN₂, respectively. The values of k ^OH ₃₃ /k ₃₁range between 0.6 × 10^–2for MeOH to 6.0 for iso-PrOH at 70°C in acetonitrile. The donation of electron density to the alcohol hydroxyl group favors the attack of Ph₂COO; that is, Ph₂COO reacts as an electrophile.     

Reactivity of aromatic compounds toward diphenylcarbonyl oxide

The reactivity of organic compounds (PhH, PhMe, PhF, PhCl, PhOH, PhOEt, PhCHO, Ph₂CO, PhCN, Ph₂S, Ph₂SO, Ph₂SO₂, andp-Me₂C₆H₄) toward diphenylcarbonyl oxide Ph₂COO was characterized by thek ₃₃/k ₃₁ ratio, wherek ₃₃ andk ₃₁ are the rate constants for the reactions of Ph₂COO with the arene and diphenyldiazomethane Ph₂CN₂, respectively. The values ofk ₃₃/k ₃₁ vary from 2.6·10⁻³ (PhCN) to 0.65 (Ph₂S) (70°C, MeCN). The reaction is preceded by formation of a complex with charge transfer from a substrate to Ph₂COO. In the reactions with aromatic substances (except for Ph₂SO, PhCHO, and Ph₂CO), carbonyl oxide behaves as an electrophile. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2201, November, 1998.     

Manganese(II), nickel(II), and cadmium(II) coordination polymers with tetrafluoroterephthalate: syntheses,crystal structures,and luminescence properties

Three new coordination polymers, [Mn(BDC-F₄)(DMF)₂(H₂O)₂] _n (1), [Ni(BDC-F₄)(DMF)(EtOH)] _n (2), and [Cd(BDC-F₄)(DMF)(EtOH)] _n (3), have been synthesized by assembling transition metal salts with the rigid ligand tetrafluoroterephthalic acid (H₂BDC-F₄) in mixed EtOH/DMF solvent at pH ca. 2. For complex 1, the octahedral coordination geometry of the Mn^II center is provided by two oxygen atoms from two dianionic BDC-F₄ ligands, two DMF ligands and two aqua ligands, giving a 1-D linear chain array. For complex 2, the Ni^II center is coordinated by two dianionic BDC-F₄ ligands, two EtOH ligands and two DMF ligands, resulting in a 1-D chain structure. For complex 3, the Cd^II center is coordinated by four dianionic BDC-F₄ ligands, one EtOH ligand and one DMF ligand, generating a 2-D layered structure. The results suggest that both the metal and the solution pH play an important role in the formation of the complexes. The spectroscopic, thermal, and luminescence properties of the complexes have been investigated.     

Kinetics of the reaction O(3P) + SO2 + M → SO3 + M over the temperature range of 299°–440°K

Rate constants for the reaction O(³P) + SO₂ + M have been determined over the temperature range of 299°–440°K, using a flash photolysis–NO₂ chemiluminescence technique. For M?Ar, the Arrhenius expression was obtained. At room temperature k₂^Ar = (1.05 ± 0.21) × 10^?33 cm⁶/molec²·sec. In addition, the rate constants k₂ = (1.37 + 0.27) × 10^?33 cm⁶/molec²·sec, k₂ = (9.5 ± 3.0) ± 10^?33 cm⁶/molec²·sec, k₃ = (1.1 ± 0.2) ± 10^?31 cm⁶/molec²·sec, and k₃ = (2.6 ? 0.9) ± 10^?31 cm⁶/molec²·sec were obtained at room temperature where k₃^M is the rate constant for the reaction O + NO + M → NO₂ + M. The rate data are compared and discussed with literature values.     

The reactions of O(1D) with ozone and nitrous oxide

Ozone was photolyzed at room temperature in the presence of N₂O at 2537 Å and 2288 Å to produce O(¹D) atoms. These atoms can react with either O₃ or N₂O via From the quantum yield of N₂, the relative rate constants k_6a/k₆ and k₂/k₆ could be obtained, where k₆ + k_6a + k_6b. The former rate constant ratio was found to be 0.37 ± 0.03 at 2537 Å and 0.33 ± 0.03 at 2288 Å, in good agreement with an earlier report from our laboratory. The ratio k₂/k₆ was found to be 2.6 at 2537 Å, but 4.1 at 2288 Å. The difference in the two numbers, if real, may reflect differences in reactivity due to different amounts of excess translational energy in the O(¹D) atom at the two wavelengths.     

Complexing processes in M(II)-dithiomalonamide-diacetyl triple systems (M= Ni,Cu) in ethanol solution and in a metal(II)hexacyanoferrate(II) gelatin-immobilized matrix materials

The complexing processes in the M ^II -dithiomalonamide-diacetyl triple system (M=Ni, Cu) occuring in the nickel(II)- and copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous alkaline solutions (pH~12) containing dithiomalonamide and diacetyl at room temperature, and between MCl₂, dithiomalonamide and diacetyl in EtOH solutions upon heating to$80°C, have been studied. In the Ni ^II -dithiomalonamide-diacetyl system, template synthesis occurs in EtOH solution but does not occur in the gelatin-immobilized matrix, whereas in the Cu ^II -dithiomalonamide-diacetyl system, template synthesis occurs in the gelatin-immobilized matrix but not in EtOH solution. Dithiomalonamide and diacetyl are the ligand synthons in the processes indicated.     

Effects of CH3OH‐H2O and CH3OH solvents on rate of reaction of phthalimide with piperidine

Pseudo‐first‐order rate constants (k_obs) for the cleavage of phthalimide in the presence of piperidine (Pip) vary linearly with the total concentration of Pip ([Pip]_T) at a constant content of methanol in mixed aqueous solvents containing 2% v/v acetonitrile. Such linear variation of k_obs against [Pip]_T exists within the methanol content range 10%–∼80% v/v. The change in k_obs with the change in [Pip]_T at 98% v/v CH₃OH in mixed methanol‐acetonitrile solvent shows the relationship: k_obs = k[Pip]_T + k[Pip], where respective k and k represent apparent second‐order and third‐order rate constants for nucleophilic and general base‐catalyzed piperidinolysis of phthalimide. The values of k_obs, obtained within [Pip]_T range 0.02–0.40 M at 0.03 M NaOH and 20 as well as 50% v/v CH₃OH reveal the relationship: k_obs = k₀/(1 + {k_n[Pip]/k_OX[⁻OX]_T}), where k₀ is the pseudo‐first‐order rate constant for hydrolysis of phthalimide, k_n and k_OX represent nucleophilic second‐order rate constants for the reaction of Pip with phthalimide and for the XO⁻‐catalyzed cyclization of N‐piperidinylphthalamide to phthalimide, respectively, and [⁻OX]_T = [NaOH] + [⁻OX_re], where [⁻OX_re] = [⁻OH_re] + [CH₃O_re⁻]. The reversible reactions of Pip with H₂O and CH₃OH produce ⁻OH_re and CH₃O_re⁻ ions. The effects of mixed methanol‐water solvents on the rates of piperidinolysis of PTH reveal a nonlinear decrease in k with the increase in the content of methanol. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 29–40, 2001     

Mechanism of thermal decomposition of diphenyldiazomethane in the presence of oxygen

The kinetics, products, and mechanism of thermal decomposition of diphenyldiazomethane (RN₂, R=Ph₂C) in the presence of oxygen were studied. Thermolysis is accompanied by chemiluminescence. An emitter of chemiluminescence (³RO) forms in the reaction of benzophenoneO-oxide with RN₂. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 276–279, February, 1997.     

Kinetics of the DS-radical reactions with CINO and NO2

The rate constants for the reactions of the DS radical with NO₂ (reaction 1) and ClNO (reaction 2) have been measured using the discharge-flow technique at 2 torr total pressure of helium. The DS radical was monitored by laser-induced fluorescence. The reactions were found to have the following bimolecular rate constants (95% confidence level, in units of cm³ molecule^?1 s^?1): This expression for k₁ is found to be in excellent agreement with one of several previous studies. The magnitude of k₂ is examined within the framework of a well-established reactivity trend. © 1994 John Wiley & Sons, Inc.     

Synthesis,structures, sorption and magnetic properties of coordination polymers based on 3d metal pivalates and polydentate pyridine-type ligands

The reactions of 3d metal pivalates with pyridine-containing ligands of different structures afforded the 1D coordination polymers [Co₂(Piv)₄(dpe)₂] _n , [Ni(Piv)₂(dpe)(EtOH)₂] _n , [Cu₂(Piv)₄(dpe)] _n , [Cu(Piv)₂(dpe)] _n , [Ni(Piv)₂(4-ptz)(EtOH)₂] _n , and [Cu₂(Piv)₄(4-ptz)· ·mSolv] _n (Solv is EtOH, m = 2; Solv is C₆H₆, m = 1; Piv^? is pivalate, dpe is trans-1,2-bis(4-pyridyl)ethylene, 4-ptz is 2,4,6-tris(4-pyridyl)-1,3,5-triazine), as well as the 3D coordination polymer [{Cu₂(Piv)₄}₃(3-ptz)₂] _n (3-ptz is 2,4,6-tris(3-pyridyl)-1,3,5-triazine). The sorption and magnetic properties of a series of the synthesized compounds and magnetic properties of the earlier characterized coordination polymer [Mn₂(O₂CC₆H₅)₄(dpe)₂·dpe] _n were studied. It was shown that the desolvation of the complexes [Ni(Piv)₂(4-ptz)(EtOH)₂] _n and [Cu₂(Piv)₄-(4-ptz)·2EtOH] _n resulted in the formation of the crystal structures, in which the pores are accessible to nitrogen and hydrogen at 78 K (S _BET are up to 92 m² g^?1). The temperature dependences of the molar magnetic susceptibility for [Co₂(Piv)₄(dpe)₂] _n , [Mn₂(O₂CC₆H₅)₄-(dpe)₂·dpe] _n , [Ni(Piv)₂(dpe)(EtOH)₂] _n , [Ni(Piv)₂(4-ptz)(EtOH)₂] _n , and [Cu₂(Piv)₄-(4-ptz)·2EtOH] _n are described in terms of models taking into account the zero-field splitting and exchange interactions or isotropic exchange Hamiltonians.     

Rate constants for some reactions of free radicals with haloacetates in aqueous solution

The kinetics of the acqueous-phase reactions of the free radicals ·OH, ·Cl, and SO· with the halogenated acetates, CH₂FCOO^?, CHF₂COO^?, CF₃COO^?, and with CH₂ClCOO^?, CHCl₂COO^?, CCl₃COO^? were investigated. Generally, the reactivity decreases with increasing halogen substitution and is in the order k(·OH) > k(SO·) > k(·Cl), but there is no general relation between the effect on reactivity of chlorine and fluorine substitution. © 1995 John Wiley & Sons, Inc.     

The method of asymptotic approximations as applied to analyzing the mechanism of inhibited liquid-phase oxidation

A new method for analyzing the problems of chemical kinetics is elaborated involving the technique of mathematical modeling. Namely, the matching method of the asymptotic expansion is applied to analyzing the inhibition mechanism of oxidation. The proposed approach is an extension of the well-known method of quasi-stationary concentrations and may be applied to study a series of problems in the field of chemical kinetics. Three different time scales were established for the mechanism of inhibited oxidation under restrictions k₇[InH]₀/(2k₆W_i)^1/2 ? 1 and k₈ ? 2k₆ ? k₇. At the first time scale (that is very fast and is measured in second fractions) the concentration of radicals In only changes while [RO₂] ? [RO₂]₀, [In H] ? [In H]₀ are constants. At the second time scale (s), [RO₂] changes while [In] ? [In]_st, [In H] ? [In H]₀ are constants. At the third time scale (min), [In H] changes. An asymptotic analysis of the differential equations allows us to find out both the time duration of each step and the variation of the component which changes at this step. After that the rate constants k₈, 2k₆, k₇ are determined from comparison with the experimental measurements of [In], [RO₂], and [In H]. Due to the simplicity and efficiency of the asymptotic method, one may be applied to treating the complex multicenter radical chain processes such as conjugated oxidation, radical copolymerization, sulfoxidation, etc. © 1993 John Wiley & Sons, Inc.     

The gas phase reactions of hydroxyl radicals with a series of aliphatic ethers over the temperature range 240–440 K

Absolute rate constants were determined for the gas phase reactions of OH radicals with a series of linear aliphatic ethers using the flash photolysis resonance fluorescence technique. Experiments were performed over the temperature range 240–440 K at total pressures (using Ar diluent gas) between 25–50 Torr. The kinetic data for dimethylether (k₁), diethylether (k₂), and dipropylether (k₃) were used to derive the Arrhenius expressions and At 296 K, the measured rate constants (in units of 10^?13 cm³ molecule^?1 s^?1) were: k₁ = (24.9 ± 2.2), k₂ = (136 ± 9), and k₃ = (180 ± 22). Room temperature rate constants for the OH reactions with several other aliphatic ethers were also measured. These were (in the above units): di-n-butylether, (278 ± 36); di-n-pentylether, (347 ± 20); ethyleneoxide, (0.95 ± 0.05); propyleneoxide, (4.95 ± 0.52); and tetrahydrofuran, (178 ± 16). The results are discussed in terms of the mechanisms for these reactions and are compared to previous literature data.     

Isostructural triazenido complexes of first row transition metals. Part 3. Low spin cyclopentadienyl complexes of cobalt(II) (η5-C5H5)(PPh3)(RN3R)Co

Summary Reaction of (PPh₃)₂Cl₂Co^II with TlC₅H₅ gave the new ( ⁵-C₅H₅)(PPh₃)ClCo^II complex. This complex reacted with Ag(RN₃R) or Cu(RN₃R) (R=p-MeC₆H₄,p-ClC₆H₄ or 3,5-Cl₂C₆H₃) to give the novel compounds ( ⁵-C₅H₅)(PPh₃)(RN₃R)Co^II, with a spin state of one half, which are representatives of the very small class of paramagnetic monocyclopentadienyl transition metal complexes. The structural conclusions are based on comparison with the isostructural [ ⁵-C₅H₅)(PPh₃)(RN₃R)Co^III]PF₆ complex, on the i.r. spectra and on the observed redox behaviour. The e.p.r. spectra are reported, but are not well enough resolved for the determination of the hyperfine interactions. The orbital scheme of the new complex is discussed in terms of a distorted octahedral crystal field in relation to the series of isostructural ( ⁵-C₅H₅)(PPh₃)(RN₃R)M^II (M = Fe, Co or Ni) complexes.     

Spectrophotometric investigation of nickel(II) chloro complexes in alcoholic solutions

Summary A spectrophotometric study of Ni^II chloro complexes in the u.v.-vis. region was carried out at 25 °C and constant ionic strength of 1 mol dm^–3. A matrix rank treatment method was used to identify two successive mononuclear complexes, NiCl⁺ and NiCl₂, in the three alcohols studied viz. MeOH, EtOH and i-PrOH. The best values for the apparent overall stability constants, _j , were calculated using a program based on the least-squares method. The log ₁ and log ₂ values in MeOH, EtOH and i-PrOH are 1.3 and 1.2, 1.7 and 1.8, and 1.9 and 2.2, respectively. The stability increases directly with the mol. wt. of the solvent, or decreases as a linear function of the permittivity of the pure solvent. The electronic spectra and the formation curves of the two complexes in MeOH solutions were calculated.     

Conductance of electrolytes in ethanol solutions from −45 to 25°C

Precise conductance data for solutions of NaI, NaBPh₄, KI, KSCN, Csl, Pr₄NI, Pr₄NBr, Pr₄NClO₄, i-Am₃BuNI, and i-Am₃BuNBPh₄ in ethanol at ?45, ?35, ?25, ?15, ?5, 5, 15, and 25°C are communicated and discussed. Measurements were carried out by procedures and equipment known to produce data of high precision. Evaluation of the data is performed on the basis of a conductance equation that includes terms in c^3/2. Single ion conductances are determined with the help of temperature dependent transference numberts t₀ ⁺ (KSCN/EtOH). Ion-pair association constants and their temperature dependence are discussed in terms of contact and solvent separated ion pairs and the role of non-Coulombic forces is demonstrated with the help of an appropriate splitting of the Gibb's energy of ion-pair formation.     

Calculation of activation volumes of thermal conversions of trimethylsilyl(cumyl) peroxide by the spline approximation method

The overall rate constants k_s of thermal conversions of trimethylsilyl(cumyl) peroxide (TMSCP) at pressures P up to 10 kbar are separated into components taking into account the ratios of the corresponding products: the rate constants of radical decomposition k_d and the rate constant of rearrangement k _r. Spline approximation of experimental dependences of lnk on P is used to determine the continuous dependence of the activation volume V^# on P in the solvents cyclohexane, anisole, toluene, n-nonane, isopropylbenzene, and tert-butylbenzene. The dependences of V_s^#, V_d^#, V_r^# on P are synchronous and nonordinary, and their nature significantly depends on the choice of a solvent. Spline approximation of experimental dependences of the TMSCP concentrations on the reaction time in isopropylbenzene at various P is used to find differential constants k_s , which generally increase with the reaction time, especially in the pressure interval 5–10 kbar.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 836–841.Original Russian Text Copyright © 2004 by Zhulin, Rudakov, Antonovskii.     

A kinetic study of the complex formation between aquachromium(III) ions and L-iso-leucine

Summary The kinetics of complex formation between aquachromium(III) ions and L-iso-leucine have been studied spectrophotometrically. Effects of varying the total chromium(III), total amino acid and H⁺ concentrations, ionic-strength, temperature and % EtOH on the k_ohs were determined. The results are best accounted for by outer-sphere complexation equilibria involving HL (the amino acid zwitterion) and [Cr(H₂O)₆]³⁺/[Cr(H₂O)₅OH]²⁺ which precede anations. A rate-equation is established which involves K_os1, K_os2, k₁, k₂ (the respective outer-sphere complexation and interchange rate constants with [Cr(H₂O)₆]³⁺ and [Cr(H₂O)₅OH]²⁺), K_a and K_h (the acid-dissociation constants of H₂L⁺HL and [Cr(H₂O)₆]³⁺ [Cr(H₂O)₅OH]²⁺ pairs). The proposed mechanism is I_a for the path involving hexaaqua- and I_d for that involving hydroxopentaaquachromium(III).