Absolute Rate Constants for the Addition of Cyanomethyl (·CH2CN) and (tert-Butoxy)carbonylmethyl (·CH2CO2C(CH3)3) radicals to alkenes in solution

Absolute rate constants and their temperature dependence were determined by time-resolved electron spin resonance for the addition of the radicals ·CH₂CN and ·CH₂CO₂C(CH₃)₃ to a variety of mono- and 1,1-disubstituted and to selected 1,2- and trisubstituted alkenes in acetonitrile solution. To alkenes CH₂?CXY, ·CH₂CN adds at the unsubstituted C-atom with rate constants ranging from 3.3·10³ M ^?1S ^?1 (ethene) to 2.4·10⁶ M ^?1S ^?1 (1,1-diphenylethene) at 278 K, and the frequency factors are in the narrow range of log (A/M ^?1S ^?1) = 8.7 ± 0.3. ·CH₂CO₂C(CH₃)₃ shows a very similar reactivity with rate constants at 296 K ranging from 1.1·10⁴ M ^?1S ^?1 (ethene) to 10⁷ M ^?1S ^?1 (1,1-diphenylethene) and frequency factors log (A/M ^?1S ^?1) = 8.4 ± 0.1. For both radicals, the rate constants and the activation energies for addition to CH₂?CXY correlate well with the overall reaction enthalpy. In contrast to the expectation of an electro- or ambiphilic behavior, polar alkene-substituent effects are not clearly expressed, but some deviations from the enthalpy correlations point to a weak electrophilicity of the radicals. The rate constants for the addition to 1,2- and to trisubstituted alkenes reveal additional steric substituent effects. Self-termination rate data for the title radicals and spectral properties of their adducts to the alkenes are also given.     

Rate constants for one-electron oxidation by methylperoxyl radicals in aqueous solutions

Rate constants for one-electron oxidation by the methylperoxyl radicals (CH₃O₂, HOCH₂O₂, ^?O₂CCH₂O₂, and CCI₃O₂) in aqueous solutions have been measured by pulse radiolysis and found to be in the range of 3 × 10⁵ to 6 × 10⁸ M^?1 s^?1 for compounds with redox potentials between 0.6 and 0.1 V. Substitution on the methylperoxyl radical with OH or CO₂^? has only a minor effect on the rate of oxidation but substitution with three chlorines increases the rate constants by two orders of magnitude. The redox potential of the CH₃O₂ radical is estimated to be 0.6–0.7 V.     

Sulfur-alkylation-initiated CpRu thiyl radicals

The formation of thiyl radicals from [Cp^∗Ru^III{κ³SSS′-tpdt}] (1A) and [Cp^∗Ru^III{κ³SSN-apdt}] (1B) {Cp^∗ = η⁵-C₅Me₅; tpdt = S(CH₂CH₂S⁻)₂; apdt = HN(CH₂CH₂S⁻)₂} has been initiated by thiolate alkylation or oxidation with iodine. Subsequent electron transfer processes yielded disulfide-bridged dinuclear complexes. The mechanistic pathways of these processes will be discussed.     

Reactivity of monoenic and conjugated diene systems present in unsaturated olefin terpolymers—I. Reactions with t-butoxy radicals (CH3)3 CO•

The relative rate constants for the hydrogen abstraction and the double bond addition reactions of t-butoxy radicals (CH₃)₃ CO^? with the model compounds 5-ethylidennorbornane (I), dihydrodicyclopentene (II), isopropylidendicyclopentene (III) and methylcyclopentadienylnorbornylmethane (IV) have been determined by using as a reference reaction the hydrogen abstraction for iso-octane. With (I), (III) and (IV) the predominant process is the hydrogen abstraction, whilst for (II) both mechanisms are important. The results have been applied for the elucidation of some aspects of the initiating mechanism of peroxide-induced cross-linking of EPDM and EPTM terpolymers containing (I)-(IV) pendants.     

STUDIES ON THE BACTERIAL ACTIVITY OF COBALT(III) COMPLEXES. PART III. COBALT(III) CARBOXYLATE COMPLEXES

Abstract

Cobalt(III) complexes of the type [Co(en)₂(chel)]X.nH₂O where en = ethylenediamine, chel = phthalato = C₆H₄CO₂)^2? ₂, maleato = (O₂CCH = CHCO₂)^2?, succinato = (O₂CCH₂CH₂CO₂)^2?, homophthalato = (O₂CC₆H₄(CH₂)CO₂)^2?, citraconato = (O₂CC(CH₃) = CHCO₂)^2?, itaconato = (CH₂ = C(CO₂)CH₂CO₂)^2?, X = NO^? ₃, Br^?, (O₂CC₆H₄CO₂H)^?, (O₂CHC = CHCO₂H)^?, (O₂C(CH₂)₂CO₂H)^?, (O₂CC₆H₄(CH₂)CO₂H)^?, (O₂CHC = C(CH₂)-CO₂H)^?, and (O₂C-CH₂?C(= CH₂)-CO₂H)^?, [Co(en)₂(malonato)]X.2H₂O (where malonato = (O₂CCH₂CO₂)^2?, X = Cl^?, Br^?, and NO^? ₃) and [Co(en)₂CO₃]Cl.2H₂O have been investigated for their bacterial activity against Escherichia coli B growing on EMB agar and in minimal glucose media both in lag and log phases. Among the most active are where chel = phthalato and homophthalato. The effects are distinct from those known for compounds of Pt, e.g., cis?[Pt(NH₃)₂Cl₂] and rhodium, e.g., trans?[Rh(C₅H₅N)₄,Cl₂].6H₂O. Antagonisms are reported.     

Preparation and reactions of [2,2-bis(carbethoxy)propyl]cyclopentadienyldicarbonyliron

Although

, (Fp  η-C₅H₅Fe(CO)₂) (I) is stable and characterizable, the lower homologue FpCH₂CH(CO₂CH₃)₂ (II) is not; this we attribute to a facile elimination reaction resulting from the relatively acidic β-hydrogen of II. Formation of I from Fp^? and XCH₂CE₂CH₃ (X  Br, Cl; E  CO₂CH₂CH₃) and cleavage of its FeC bonds (using H⁺, Br₂, Ce^IV and Hg^II) occur without major amounts of ester group migrations, even though ·CH₂CE₂CH₃ radicals are involved in some of these reactions.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

Base hydrolysis of (αβ S)-(o-methoxy benzoato) (tetraethylenepentamine) cobalt(III) ion: A comparative study of the role of ion pairs and micelles

The kinetics of base hydrolysis of (αβ S)-(o -methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: k_obs = k_OH[OH^?], in the range 0.05 ? [OH^?]_T, mol dm^?3 ? 1.0, I = 1.0 mol dm^?3, and 20.0–40.0°C. At 25°C, k_OH = 13.4 ± 0.4 dm³ mol^?1 s^?1, ΔH^≠ = 93 ± 2 kJ mol^?1 and ΔS^≠ = 90 ± 5 JK^?1 mol^?1. Several anions of varying charge and basicity, CH₃CO₂^?, SO₃^2?, SO₄^2?, CO₃^2?, C₂O₄^2?, CH₂(CO₂)₂^2?, PO₄^3?, and citrate^3? had no effect on the rate while phthalate^2?, NTA^3?, EDTA^4?, and DTPA^5? accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X-100) micelles, however, retarded the reaction, the effect being in the order SDS> CTAB > Triton X-100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo-phases which control the rate are discussed. © 1994 John Wiley & Sons, Inc.     

Spin-adducts of radicals ·P(O)(OPri)2 and ·CMe3 with pyrrolidino[60]fullerenes studied by ESR spectroscopy

The addition of the ^·Bu^t (R¹) and ^·P(O)(OPrⁱ)₂ (R²) radicals to pyrrolidino[60]fullerenes C₆₀CH₂NMeCHX (X = C₆H₄N(CH₂CH₂Cl)₂, 2,6-(Bu^t)₂C₆H₂OH, PhC₆H₄, and indol-3-yl) was studied by ESR spectroscopy. The rate constants of R¹ radical addition to these compounds and dimerization of spin-adducts of the R¹ radicals with pyrrolidino[60]fullerenes were determined. Pyrrolidino[60]fullerenes manifest considerably higher reactivity toward the R¹ radicals than fullerene C₆₀ and methanofullerenes C₆₀CX¹X² (X¹ = X² = CO₂Et; X¹ = CO₂Me, X² = OP(OMe)₂, X¹ = X² = OP(OEt)₂).     

Metallkomplexe mit biologisch wichtigen Liganden. CLVII [1] Halbsandwich‐Komplexe mit Isocyanoacetylaminosäureestern und Isocyanoacetyldi‐ und tripeptidestern („Isocyano‐Peptide”︁)

Metal Complexes of Biologically Important Ligands, CLVII [1] Halfsandwich Complexes of Isocyanoacetylamino acid esters and of Isocyanoacetyldi‐ and tripeptide esters (?Isocyanopeptides”?) N‐Isocyanoacetyl‐amino acid esters CNCH₂C(O) NHCH(R)CO₂CH₃ (R = CH₃, CH(CH₃)₂, CH₂CH(CH₃)₂, CH₂C₆H₅) and N‐isocyanoacetyl‐di‐ and tripeptide esters CNCH₂C(O)NHCH(R¹)C(O)NHCH(R²)CO₂C₂H₅ and CNCH₂C(O)NHCH(R¹)C(O)NHCH (R²)C(O)NHCH(R³)CO₂CH₃ (R¹ = R² = R³ = CH₂C₆H₅, R² = H, CH₂C₆H₅) are available by condensation of potassium isocyanoacetate with amino acid esters or peptide esters. These isocyanides form with chloro‐bridged complexes [(arene)M(Cl)(μ‐Cl)]₂ (arene = Cp*, p‐cymene, M = Ir, Rh, Ru) in the presence of Ag[BF₄] or Ag[CF₃SO₃] the cationic halfsandwich complexes [(arene)M(isocyanide)₃]⁺X^? (X = BF₄, CF₃SO₃).     

UV absorption spectra of HO2, CH3O2, C2H5O2, and CH3C(O)CH2O2 radicals and mechanism of the reactions of F and Cl atoms with CH3C(O)CH3

Pulse radiolysis techniques were used to measure the gas phase UV absorption spectra of the title peroxy radicals over the range 215–340 nm. By scaling to σ(CH₃O₂)_{240 nm} = (4.24 ± 0.27) × 10^?18, the following absorption cross sections were determined: σ(HO₂)_{240 nm} = 1.29 ± 0.16, σ(C₂H₅O₂)_{240 nm} = 4.71 ± 0.45, σ(CH₃C(O)CH₂O₂)_{240 nm} = 2.03 ± 0.22, σ(CH₃C(O)CH₂O₂)_{230 nm} = 2.94 ± 0.29, and σ(CH₃C(O)CH₂O₂)_{310 nm} = 1.31 ± 0.15 (base e, units of 10^?18 cm² molecule^?1). To support the UV measurements, FTIR‐smog chamber techniques were employed to investigate the reaction of F and Cl atoms with acetone. The F atom reaction proceeds via two channels: the major channel (92% ± 3%) gives CH₃C(O)CH₂ radicals and HF, while the minor channel (8% ± 1%) gives CH₃ radicals and CH₃C(O)F. The majority (>97%) of the Cl atom reaction proceeds via H atom abstraction to give CH₃C(O)CH₂ radicals. The results are discussed with respect to the literature data concerning the UV absorption spectra of CH₃C(O)CH₂O₂ and other peroxy radicals. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 283–291, 2002     

Kinetics of reactions between methoxycarbonyl,methyl, and methoxy radicals formed in flash photolysis of dimethyl oxalate in gas phase

Flash photolysis of dimethyl oxalate produced the radicals CH₃, CH₃O, and COOCH₃. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40-torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO₂, CH₄, C₂H₄, C₂H₆, CH₂O, CH₃OH, CH₃OCH₃, HCOOCH₃, CH₃COOCH₃, CH₃OCOOCH₃, CH₃C₆H₁₁, and CH₃OC₆H₁₁. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals, k₁ = 2.7 × 10¹⁰ dm³ mol^?1 s^?1, measured with the same equipment. The rate coefficients for reactions (5)–(8) are:      

Beiträge zur Komplexchemie der Phosphine und Phosphinoxide. XXIII. Schwermetallkomplexe des Tetramethyl-biphosphins

On the coordination chemistry of phosphines and phosphinoxides. XXIII. Heavy metal complexes of tetramethyl-biphosphine The reactions of tetramethyl-biphosphine with salts of 3d elements including Cd and Hg, too, in THF, benzene, acetonitrile and alcohols, respectively, results in forming complexes of differing compositions: (MⁿX_n)₂{(CH₃)₂P? P(CH₃}₂)₃? Mⁿ = Ti^III, V^III, Cr^III, Fe^II, Ni^II, Cu^I; MX₂{(CH₃)₂P? P(CH₃)₂}₂? M = Co^II, Ni^II, Hg^II; MX₂ · (CH₃)₂P? P(CH₃)₂? M = Fe^II, Ni^II, Zn, Cd, Hg^II; X = Cl, Br, J. The partly intensively coloured complexes have low solubilities; this item complicates the performing of structure determining methods. Partial informations about the structures of the complexes are to be gained by magnetic and spectrophotometric measurements and X-ray investigations. The tendency of (CH₃)₂P? P(CH₃)₂ to form complexes with transition metals differs from that of other biphosphines. Splitting of the P? P bond due to metal salts does not occur. (CH₃)₂P? P(CH₃)₂ acts as a monodentate or bidentate ligand, like other members of the R₂P? PR₂ series do too. The forming of ligand bridges seems to be favoured in comparison to the chelate function.     

A spectrokinetic study of CH2I and CH2IO2 radicals

The UV absorption spectrum and kinetics of CH₂I and CH₂IO₂ radicals have been studied in the gasphase at 295 K using a pulse radiolysis UV absorption spectroscopic technique. UV absorption spectra of CH₂I and CH₂IO₂ radicals were quantified in the range 220–400 nm. The spectrum of CH₂I has absorption maxima at 280 nm and 337.5 nm. The absorption cross-section for the CH₂I radicals at 337.5 nm was (4.1 ± 0.9) × 10^?18 cm² molecule^?1. The UV spectrum of CH₂IO₂ radicals is broad. The absorption cross-section at 370 nm was (2.1 ± 0.5) × 10^?18 cm² molecule^?1. The rate constant for the self reaction of CH₂I radicals, k = 4 × 10^?11 cm³ molecule^?1 s^?1 at 1000 mbar total pressure of SF₆, was derived by kinetic modelling of experimental absorbance transients. The observed self-reaction rate constant for CH₂IO₂ radicals was estimated also by modelling to k = 9 × 10^?11 cm³ molecule^?1 s^?1. As part of this work a rate constant of (2.0 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1 was measured for the reaction of F atoms with CH₃I. The branching ratios of this reaction for abstraction of an I atom and a H atom were determined to (64 ± 6)% and (36 ± 6)%, respectively. © 1994 John Wiley & Sons, Inc.     

Synthesis,light emission,and photovoltaic properties of perylene‐containing polyacetylenes

Perylene (Py)‐containing polyacetylenes with different skeleton structures ? [HC?C(C₆H₄)CO₂? Py]_n? (P 1 ), ? [HC?C(CH₂)₈CO₂? Py]_n? (P 2 ), and ? {[(C₆H₅) C?C(CH₂)₉NH₂]? co? [(C₆H₅)C?C(CH₂)₉? Py]}_n? (P 3 ) are synthesized in satisfactory yields by Rh‐catalyzed polymerization (for P 1 and P 2 ) and polymer reaction (for P 3 ). All the polymers are soluble and possess high molecular weights (M_w up to 2.8 × 10⁵). Their structures and properties are characterized and evaluated by IR, NMR, UV, TGA, PL, and photovoltaic (PV) analyses. The polymers are thermally stable, losing little of their weights when heated to 330 °C. When their solutions are irradiated, their perylene pendants emit intense red fluorescence at 610 nm. PV cells with a configuration of ITO/PEDOT:PSS/polymer/LiF/Al are fabricated, which show maximum current density of 10.3 μA/cm². The external quantum efficiency is sensitive to the polymer structure, with P 3 exhibiting the highest value of 0.23%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2025–2037, 2008     

Rate constants for addition of the OP·(OPri)2, Me3C·, and Me(CH2)3 ·CH2 radicals to methano[60]fullerenes C60CX1X2 (X1 = X2 = CO2Et; X1 = CO2Me,X2 = OP(OMe)2; X1 = X2 = OP(OEt)2)

The rate constants for the addition of the OP^·(OPrⁱ)₂, Me₃C^·, and Me(CH₂)₃ ^·CH₂ radicals to the methano[60]fullerenes C₆₀CX¹X² (X¹ = X² = CO₂Et; X¹ = CO₂Me, X² = OP(OMe)2; X¹ = X² = OP(OEt)₂) were determined by ESR spectroscopy. Methanofullerenes are more reactive toward these radicals than C₆₀ fullerene.     

Sorption and partial molar volumes of gases in poly(ethylene-co-vinyl acetate)

Sorption and dilation properties of polymer-gas systems involving poly(ethylene-co-vinyl acetate) and N₂, CH₄, or CO₂, have been investigated at pressures up to 50 atm at temperatures of 10–40°C. Sorption isotherms for low-solubility gases (i.e., CH₄ and N₂) can be described by Henry's law, and those for high-solubility gas (i.e., CO₂) by Flory-Huggins dissolution equation. Dilation isotherms are similar in contour to the corresponding sorption isotherms. From the obtained sorption and dilation data, partial molar volumes of the gases in the polymer were determined as a function of temperature. Thermal expansivity of dissolved CO₂ molecules was estimated at ca. 2.4 × 10^?3°C^?1 from the temperature dependence of partial molar volume. The expansivity is smaller than that of liquid CO₂ and larger than those of the polymer and organic liquids. © 1994 John Wiley & Sons, Inc.     

Kinetics and Mechanism of the Reaction of Chloroplatinum(II) Complexes with Alkyl Radicals

The reaction between certain platinum(II) complexes and alky radicals produces an unstable organoplatinum(III) intermediate, {Pt^III -R}. The kinetics of this step were evaluated by laser flash photolysis with ABTS² (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) ion) and TMPD (tetramethylphenylenediamine) as kinetic probes. The rate constants for PtCl₄^2? are: k_Pt/10⁸ L mol^?1 s^?1 = 5.2, 2.8 and 0.27 for CH_3, C₂H₅, and CH₂Cl in aqueous solution at pH 1. Those with cis-Pt(NH₃)₂Cl₂ are somewhat smaller, and those for Pt(NH₃)₄²⁺ too small to measure will) this technique. The product analysis indicates that the decomposition of organoplatinum takes place by hydrolysis and (for R = C₂H₅ only) by β-elimination, The kinetic isotope effect on die β-elimination of DCH₂CH₂PtC₄,^2? is k_H/k_D = 1.2. The β-elimination step produces a Pt^III-hydride that releases hydrogen gas and forms {Pt_III-OH}. The short-lived Pt(III) intermediate may disproportionate or oxidize the Co^II complex that is produced in the radical-generating step.     

Photolysis of poly(ethylene terephthalate)

The photolysis of poly(ethylene terephthalate) films was studied in vacuo with light of wavelengths 2537 and 3130 A. A very stable filter system which cuts out the 3025 A. line was developed to isolate 3130 A. from a mercury spectrum. Despite the fact that the penetration of 2537 A. light was limited to a depth of a ca. 10³ A. whereas 3130 A. light was more uniformly absorbed it was possible to demonstrate that the quantum yields for CO and CO₂ formation were in agreement for the two wavelengths. Quantum yields for fractures and crosslinks were estimated by sol-gel analysis. An absorption maximum which develops near 13 μ after exposure of poly(ethylene terephthalate) to light or γ-rays was attributed to the formation of groups formed by elimination of CO and CO₂. ESR spectra for trapped radicals were tentatively assigned to the components p-C₆H₃· and ·O? CH₂? CH₂? . It is suggested that the former radicals combine to form crosslinks. Quantum yields (× 10⁴) with 3130 A. light are: CO, 6; CO₂, 2; crosslinks, 5.5; trapped radicals, 1.5; With 2537 A. light, quantum yields are: CO, 6–9; CO₂, 2–3; the network formed was not characterized as to crosslinks and fractures; trapped radicals were observed to exist but not determined.     

The antioxidant reactivity of sorbitylfurfural towards potential harmful radicals,studied by radiation chemistry techniques

Ionising radiations, employed in a broad range of dose-rate, together with a complex non-linear computation of reaction mechanisms, allow the determination of boundary values of rate constants concerning sorbitylfurfural (SF) reactivity towards a wide series of oxidant and/or virtually harmful radicals. SF reacts with some radicals (H, SO₄^-˙, CO₃^-˙, Br₂^-˙, CH₃˙), produced with both pulse and stationary radiolysis in neutral aqueous solution, having electrophilic and/or oxidative behaviour. The rate constants range from diffusional (k = (7-9) × 10⁹ M^-1 s^-1) to relatively low values (k = 2 × 10⁵ M^-1 s^-1). The possibility to observe these reactions, by means of radiolytical techniques, is heavily influenced by dose-rate. A relation between the radical E⁰_NHE and their reactivity with SF is hinted.