Arrhenius parameters for the gas‐phase reactions of O3 with two butenes and two methyl‐substituted butenes over the temperature range of 295–351 K

Gas‐phase reactions of ozone with two butenes (1‐butene and isobutene) and two methyl‐substituted butenes (2‐methyl‐1‐butene and 3‐methyl‐1‐butene) have been studied in an indoor chamber at 295–351 K. The O₃ concentrations were monitored by Model 49C‐Ozone analyzer. The butene concentrations were measured by gas chromatography–flame ionization detector. The Arrhenius expressions of k=3.50×10^?15e^{(?1756±84)/T} cm³ molecule^?1 s^?1, k=3.39×10^?15e^{(?1697±52)/T} cm³ molecule^?1 s^?1, k=6.18×10^?15e^{?(1822±80)/T} cm³ molecule^?1 s^?1, and k=7.24×10^?14e^{?(2741±139)/T} cm³ molecule^?1 s^?1 were obtained for the ozonolysis reactions of 1‐butene, isobutene, 2‐methyl‐1‐butene, and 3‐methyl‐1‐butene, respectively. Both the reaction rate constant and activation energy obtained in this work are in good agreement with those reported by using different techniques in the literature. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 238–246, 2011     

Temperature and pressure effects on the kinetics of the Bromate ion-iodide ion-L-ascorbic acid clock reaction

The kinetics of the bromate ion-iodide ion-L-ascorbic acid clock reaction was investigated as a function of temperature and pressure using stopped-flow techniques. Kinetic results were obtained for the uncatalyzed as well as for the Mo(VI) and V(V) catalyzed reactions. While molybdenum catalyzes the BrO-I^? reaction, vanadium catalyzes the direct oxidation of ascorbic acid by bromate ion. The corresponding rate laws and kinetic parameters are as follows. Uncatalyzed reaction: r₂ = k₂[BrO] [I^?][H⁺]², k₂ = 38.6 ± 2.0 dm⁹ mol^?3 s^?1, ΔH? = 41.3 ± 4.2 kJmol^?1, ΔS? = ?75.9 ± 11.4 Jmol^?1 K^?1, ΔV? = ?14.2 ± 2.9 cm³ mol^?1. Molybdenum-catalyzed reaction: r′₂ = k₂[BrO] [I^?] [H⁺]² + k_Mo[BrO] [I^?] [ H⁺]²[M₀(VI)], k_Mo = (2.9 ± 0.3)10⁶ dm¹² mol^?4 s^?1, ΔH? = 27.2 ± 2.5 kJmol^?1, ΔS? = ?30.1 ± 4.5 Jmol^?1K^?1, ΔV? = 14.2 ± 2.1 cm³ mol^?1. Vanadium-catalyzed reaction: r′₁ = k_V[BrO] [V(V)], k_V = 9.1 ± 0.6 dm³ mol^?1 s^?1, ΔH? = 61.4 ± 5.4 kJmol^?1, ΔS? = ?20.7 ± 3.1 Jmol^?1K^?1, ΔV? = 5.2 ± 1.5 cm³ mol^?1. On the basis of the results, mechanistic details of the BrO-I^? reaction and the catalytic oxidation of ascorbic acid by BrO are elaborated. © 1995 John Wiley & Sons, Inc.     

Studies on the composition and kinetics of chromium(III)-alanine system

Kinetics of the complex formation of chromium(III) with alanine in aqueous medium has been studied at 45, 50, and 55°C, pH 3.3–4.4, and μ = 1 M (KNO₃). Under pseudo first-order conditions the observed rate constant (k_obs) was found to follow the rate equation: Values of the rate parameters (k_an, k, K_IP, and K) were calculated. Activation parameters for anation rate constants, ΔH^≠(k_an) = 25 ± 1 kJ mol^?1, ΔH^≠(k) = 91 ± 3 kJ mol^?1, and ΔS^≠(k_an) = ?244 ± 3 JK^?1 mol^?1, ΔS^≠(k) = ?30 ± 10 JK^?1 mol^?1 are indicative of an (I_a) mechanism for k_an and (I_d) mechanism for k routes (‥substrate Cr(H₂O) is involved in the k route whereas Cr(H₂O)₅OH²⁺ is involved in k′ route). Thermodynamic parameters for ion-pair formation constants are found to be ΔH°(K_IP) = 12 ± 1 kJ mol^?1, ΔH°(K) = ?13 ± 3 kJ mol^?1 and ΔS°(K_IP) = 47 ± 2 JK^?1 mol^?1, and ΔS°(K) = 20 ± 9 JK^?1 mol^?1.     

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.     

Kinetics for the gas‐phase reactions of OH radicals with the hydrofluoroethers CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2 at 268–308 K

Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH₂FCF₂OCHF₂(k₁), CHF₂CF₂OCH₂CF₃ (k₂), CF₃CHFCF₂OCH₂CF₃(k₃), and CF₃CHFCF₂OCH₂CF₂CHF₂(k₄) by using a relative rate method. OH radicals were prepared by photolysis of ozone at UV wavelengths (>260 nm) in 100 Torr of a HFE–reference–H₂O–O₃–O₂–He gas mixture in a 1‐m³ temperature‐controlled chamber. By using CH₄, CH₃CCl₃, CHF₂Cl, and CF₃CF₂CF₂OCH₃ as the reference compounds, reaction rate constants of OH radicals of k₁ = (1.68) × 10^?12 exp[(?1710 ± 140)/T], k₂ = (1.36) × 10^?12 exp[(?1470 ± 90)/T], k₃ = (1.67) × 10^?12 exp[(?1560 ± 140)/T], and k₄ = (2.39) × 10^?12 exp[(?1560 ± 110)/T] cm³ molecule^?1 s^?1 were obtained at 268–308 K. The errors reported are ± 2 SD, and represent precision only. We estimate that the potential systematic errors associated with uncertainties in the reference rate constants add a further 10% uncertainty to the values of k₁–k₄. The results are discussed in relation to the predictions of Atkinson's structure–activity relationship model. The dominant tropospheric loss process for the HFEs studied here is considered to be by the reaction with the OH radicals, with atmospheric lifetimes of 11.5, 5.9, 6.7, and 4.7 years calculated for CH₂FCF₂OCHF₂, CHF₂CF₂OCH₂CF₃, CF₃CHFCF₂OCH₂CF₃, and CF₃CHFCF₂OCH₂CF₂CHF₂, respectively, by scaling from the lifetime of CH₃CCl₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 239–245, 2003     

Kinetics and mechanism of the reaction of CH3O with NO

The kinetics of the reaction of CH₃O with NO and the branching ratio for HCHO product formation, obtained as Γ_HCHO = (Rate of HCHO formation) / (Rate of CH₃O decay), have been studied using a discharge flow reactor. Laser induced fluorescence has been used to monitor the decay of the CH₃O radical and the build-up of the HCHO product. Overall rate constants and product branching ratios were measured at room temperature over the pressure range of 0.72–8.5 torr He. Three reaction mechanisms were considered which differed in the routes of HCHO formation: (i) direct disproportionation; (ii) via an energized collision complex; or (iii) both reaction routes. It has been shown that data on the pressure dependence of the overall rate constant are not sufficient to distinguish between these mechanisms. In addition, an accurate value of Γ is required. Analysis of the available experimental data provided 0.0 and about 0.1 as the lower and upper limit for Γ, respectively. Since the rate constants derived for CH₃ONO formation were not sensitive to the value assumed for Γ, k = (1.69 ± 0.69) × 10^?29 cm⁶ molecule^?2 s^?1 and k = (2.45 ± 0.31) × 10^?11 cm³ molecule^?1 s^?1 could be derived. The rate constant obtained for formaldehyde formation when extrapolated to zero pressure is k = (3.15 ± 0.92) × 10^?12 cm³ molecule^?1 s^?1. © 1994 John Wiley & Sons, Inc.     

Some thermodynamic parameters for hydroxy amino acids: Bicine and tricine

pK values of N,N-dihydroxyethylglycine (bicine) and N-[tris(hydroxymethyl)methyl]-glycine (tricine) have been determined by the Irving-Rossotti method in an aqueous medium at 25, 30, 35, 40, 45, and 50°C and at different ionic strengths (I = 0.1, 0.5, and 1.0). Plots between pK_a(NH) and 1/T for various ionic strengths have been obtained and the values of slopes have been used to calculate the ΔH, ΔS, and ΔG for the dissociation reactions of bicine and tricine. The ΔH, ΔS, and ΔG values for bicine were found to be 10.6 ± 0.6 kcal mol^?1, ?1.9 ± 1.8 e.u., and 11.1 ± 0.06 kcal mol^?1, respectively, and for tricine 11.2 ± 0.6 kcal mol^?1, 1.6 ± 1.6 e.u., and 10.7 ± 0.06 kcal mol^?1, respectively. The pK_a(NH) values decrease with rise in temperature but the influence of ionic strength is not significant.     

EPR-Einkristalluntersuchungen System Fe(NO)(Et2dsc)2/In(Et2dsc)3 (Et2dsc = Diethyldiselenocarbamat). Kristall- und Molekülstruktur von Tris(diethyldiselenocarbamato)indium(III), In(Et2dsc)3

Single Crystal Electron Paramagnetic Resonance Study on the System Fe(NO)(Et₂dsc)₂/In(Et₂dsc)₃ (Et₂dsc = diethyldiselenocarbamate). Crystal and Molecular Structure of Tris(diethyldiselenocarbamato)indium(III), In^III(Et₂dsc)₃ A single-crystal EPR study (T = 295 K) of Bis(diethyldiselenocarbamato)nitrosyliron(I) incorporated in Tris(diethyldiselenocarbamato)indium(III) is reported. The tensors g an A^N have rhombic symmetry with g₁ = 2.048, g₂ = 2.058, g₃ = 2.062 and A = 9.2 · 10^?4 cm^?1, A = 10.0 · 10^?4 cm^?1, A = 11.3 · 10^?4 cm^?1. The A values are discussed in terms of spin density distribution. The x-ray crystallographic data of In^III(Et₂dsc)₃ (space group P2₁/c, a = 6.731(3) Å, b = 18.05(9) Å, c = 20.914(10) Å, α = 90.02(2)°, β = 93.74(2)° and γ = 90.01(2)°) are given.     

Low temperature 13C NMR study of 1-(3-pentyloxyphenylcarbamoyloxy)-2-dialkyl- aminocyclohexanes

Cyclohexane and piperidine ring reversal in 1-(3-pentyloxyphenylcarbamoyloxy)-2-dialkylaminocyclohexanes was investigated by ¹³C NMR. An unusually low conformational energy ΔG = 0.59 kJ mol^?1 and activation parameters ΔG^≠₂₁₈ = 43.8 ± 0.4 kJ mol^?1, ΔH^≠ = 48.9 ± 2.5 kJ mol^?1 and ΔS^≠ = 23 ± 9 J mol^?1 K^?1 were found for the diequatorial to diaxial transition of the cyclohexane ring in the trans-pyrrolidinyl derivative. In the trans-piperidinyl derivative, ΔG₂₂₂ = 44.7 ± 0.5 KJ mol^?1, ΔH^≠ = 55.7 ± 6.3 kJ mol^?1 and ΔS^≠ = 51 ± 21 J mol^?1 K^?1 was found for the piperidine ring reversal from the non-equivalence of the α-carbons.     

Rate constants for the reactions of OH radicals with CH3OCF2CF3, CH3OCF2CF2CF3, and CH3OCF(CF3)2

The rate constants for the reactions of OH radicals with CH₃OCF₂CF₃, CH₃OCF₂CF₂CF₃, and CH₃OCF(CF₃)₂ have been measured over the temperature range 250–430 K. Kinetic measurements have been carried out using the flash photolysis, laser photolysis, and discharge flow methods combined respectively with the laser induced fluorescence technique. The influence of impurities in the samples was investigated by using gas‐chromatography. The following Arrhenius expressions were determined: k(CH₃OCF₂CF₃) = (1.90) × 10⁻¹² exp[−(1510 ± 120)/T], k(CH₃OCF₂CF₂CF₃) = (2.06) × 10⁻¹² exp[−(1540 ± 80)/T], and k(CH₃OCF(CF₃)₂) = (1.94) × 10⁻¹² exp[−(1450 ± 70)/T] cm³ molecule⁻¹ s⁻¹. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 846–853, 1999     

The heats of formation of NO3− and NO3− association complexes with HNO3 and HBr

The equilibrium constant for the reaction has been determined between 331 and 480°K using a variable-temperature flowing afterglow. These data give ΔH°(1) = -1.03 ± 0.21 kcal/mol and ΔS°(1) = —4.6 ± 1.0 cal/mol°K. When combined with the known thermochemical values for HBr, Br^?, and HNO₃, this yields ΔH(NO₃^?) = -74.81 ± 0.54 kcal/mol and S(NO₃^?) = 59.4 cal/mol·°K. In addition ΔH_n-1,n and ΔS_n-1,nfor the gas-phase reactions were determined for n = 2 and 3. The implications of these measurements to gas-phase negative ion chemistry are discussed.     

Water Exchange on Hexaaquavanadium(III): a Variable-Temperature and Variable-Pressure 17O-NMR Study at 1.4 and 4.7 Tesla

Water exchange on hexaaquavanadium (III) has been studied as a function of temperature (255 to 413 K) and pressure (up to 250 MPa, at several temperatures) by ¹⁷O-NMR spectroscopy at 8.13 and 27.11 MHz. The samples contained V³⁺ (0.30–1.53 m), H⁺ (0.19–2.25 m) and ¹⁷O-enriched (10–20%) H₂O. The trifluoromethanesulfonate was used as counter-ion, and, contrary to the previously used chloride or bromide, CF₃SO is shown to be non-coordinating. The following exchange parameters were obtained: k = (5.0 ± 0.3) · 10² s^?1, ΔH* = (49.4 ± 0.8) kJ mol^?1, ΔS* = ?(28 ± 2) JK^?1 mol^?1, ΔV* = ?(8.9 ± 0.4) cm³ mol^?1 and Δβ* = ?(1.1 ± 0.3) · 10^?2 cm³ mol^?1 MPa^?1. They are in accord with an associative interchange mechanism, I_a. These results for H₂O exchange are discussed together with the available data for complex formation reactions on hexaaquavanadium(III). A semi-quantitative analysis of the bound H₂O linewidth led to an estimation of the proportions of the different contributions to the relaxation mechanism in the coordinated site: the dipole-dipole interaction hardly contributes to the relaxation (less than 7%); the quadrupolar relaxation, and the scalar coupling mechanism are nearly equally efficient at low temperature (～ 273 K), but the latter becomes more important at higher temperature (75–85% contribution at 360 K).     

Variable-Temperature and Variable-Pressure 17O-NMR Study of Water Exchange of Hexaaquaaluminium(III)

The transverse relaxation rate of H₂O in Al(H₂O) has been measured as a function of temperature (255 to 417 K) and pressure (up to 220 MPa) using the ¹⁷O-NMR line-broadening technique, in the presence of Mn(II) as a relaxation agent. At high temperatures the relaxation rate is governed by chemical exchange with bulk H₂O, whereas at low temperatures quadrupolar relaxation is prevailing. Low-temperature fast-injection ¹⁷O-NMR was used to extend the accessible kinetic domain. The samples studied contained Al³⁺ (0.5 m), Mn²⁺ (0.2–0.5 m), H ⁺ (0.2–3.1 m) and ¹⁷O-enriched (20–40%) H₂O. Non-coordinating perchlorate was used as counter ion. The following H₂O exchange parameters were obtained: k = (1.29 ± 0.04) s⁻¹, ΔH* = (84.7 ± 0.3) kJ mol⁻¹, ΔS* = +(41.6 ± 0.9) J K ⁻¹ mol⁻¹, and ΔV = +(5.7 ± 0.2) cm³ mol⁻¹, indicating a dissociative interchange, I_d, mechanism. These results of H₂O exchange on Al(H₂O) are discussed together with the available complex-formation rate data and permit also the assignment of I_d mechanisms to these latter reactions.     

Stability of Complex Metal Bromides in the gas phase and in toluene

The equilibrium constants of the reactions MBr₂(s) + Al₂Br₆(sln) ? MAl₂Br₈(sln) M = Cr, Mn, Co, Ni, Zn, Cd have been measured at 298 K in toluene. Ni: 0.017 ± 0.0024, Co: 0.54 ± 0.07, Zn: 1.5 ± 0.2, Mn: 2.1 ± 0, 7, Cr: 2.2 ± 1, Cd: 7 ± 5. They are compared with literature values of the equilibrium constants of analogous reactions in the gas phase MX₂(s) + Al₂X₆(g) ? MAl₂X₈(g), X = Cl, Br. For CoAl₂Br₈(sln) the temperature dependence of the equilibrium constant yielded Δ_fH = ?9.4 ± 1 kJ mol^?1 and Δ_fS = ?39.5 ± 3 J mol^?1 K^?1 while literature values for CoAl₂Br₈(g) are Δ_fH = 42.4 ± 2 kJ mol^?1 and Δ_fS = 42.9 ± 2 J mol^?1 K^?1. The solubility of Al₂Br₆ in toluene as well as its enthalpy of dissolution have been measured in order to evaluate ΔH° and ΔS° of the solvation of Al₂Br₆(g) and CoAl₂Br₈(g) in toluene by a thermodynamic cycle. Solvation of Al₂Br₆(g): ΔH = ?72.7 ± 1 kJ mol^?1, ΔS = ?139.6 ± 4 J mol^?1 K^?1, solvation of CoAl₂Br₈(g): ΔH = ?124.5 ± 4kJ mol^?1, ΔS = ?222 ± 9J mol^?1 K^?1. Thus, CoAl₂Br₈ interacts more strongly with the solvent toluene than Al₂Br₆ does.     

Copper Catalysed Oxygenation of Bis (2-pyridyl) methane and 6-Methyl-bis (2-pyridyl)methane to the Corresponding Ketones

The ligands (L) bis (2-pyridyl) methane (BPM) and 6-methyl-bis (2-pyridyl)methane (MBPM) form the three complexes CuL²⁺, CuL, and Cu₂L₂H with Cu²⁺. Stability constants are log K₁ = 6.23 ± 0.06, log K₂ = 4.83 ± 0.01, and log K (Cu₂L₂H + 2H²⁺ ? 2 CuL²⁺) = ?10.99 ± 0.03 for BPM and 4.56 ± 0.02, 2.64 ± 0.02, and ?11.17 ± 0.03 for MBPM, respectively. In the presence of catalytic amounts of Cu²⁺, the ligands are oxygenated to the corresponding ketones at room temperature and neutral pH. With BPM and 2,4,6-trimethylpyridine (TMP) as the substrate and the buffer base, respectively, the kinetics of the oxygenation can be described by the rate law with k₁ = (5.9 ± 0.2) · 10^?13 mol l^?1 s^?1, k₂ = (4.0 ± 0.6) · 10^?4 mol^?1 ls^?1, k₃ = (1.1 ± 0.1) · 10^?12 mol l^?1 s^?1, and k₄ = (9 ± 2) · 10^?14 mol l^?1 s^?1.     

Kinetic study of reactions of C2H5O2 with NO at 298 K and 0.55 – 2 torr

The kinetics of C₂H₅O₂ and C₂H₅O₂ radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C₂H₅O were monitored by LIF. The rate constant for C₂H₅O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k₂ = (1.25±0.04) × 10^?11, (1.66±0.06) × 10^?11, (1.81±0.06) × 10^?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm³ molecule^?1 s^?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C₂H₅O + NO + M → C₂H₅ONO + M (2a), C₂H₅O + NO → CH₃CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k_2a and for k_2b : k = (2.6±1.0) × 10^?28 cm⁶ molecule^?2 s^?1, k = (3.1±0.8) × 10^?11 cm³ molecule^?1 s^?1 and k_2b ca. 8 × 10^?12 cm³ molecule^?1 s^?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10^?27 cm⁶ molecule^?2 s^?1 recommended in air. The rate constant for the reaction C₂H₅O₂ + NO → C₂H₅O + NO₂ (3) has been measured at 1 torr of He from the simulation of experimental C₂H₅O profiles. The value obtained for k₃ = (8.2±1.6) × 10^?12 cm³ molecule^?1 s^?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc.     

Dimethylformamide-Exchange Mechanism on Some First-Row Divalent Transition-Metal Ions

The effect of temperature on the dimethylformamide exchange on Mn(DMF) and Fe(DMF) has been studied by ¹³C- and ¹⁷O-NMR, respectively, yielding the following kinetic parameters: k²⁹⁸ equals; (2.2±0.2). 10⁶ S^?1, ΔH^≠ = 34.6 ± 1.3 kJ mol^?1, ΔS^≠ = ?7.4 ± 4.8 J K^?1mol^?1 for Mn²⁺ and K²⁹⁸ = (9.7 ± 0.2).10⁵ S^?1, Delta;H^≠ = 43.0 ± 0.9 kJ mol^?1, ΔS^≠ = + 13.8 ± 2.8 J K^?1mol^?1 for Fe²⁺. The volumes of activation, ΔV^≠ in cm³mol^?1, derived from high-pressure NMR on these metal ions, together with the previously published activation volumes for Co²⁺ and Ni²⁺ (+2.4 ± 0.2 (Mn²⁺), +8.5 ± 0.4 (Fe²⁺) +9.2 ± 0.3 (Co²⁺), + 9.1 ± 0.3 (Ni²⁺)) give evidence for a dissociative activation mode for DMF exchange on these high-spin first-row transition-metal divalent ions. The small positive ΔV^≠ value observed for DMF exchange on Mn²⁺ seems to indicate that a mechanistic changeover also occurs along the series, (probably from I_d to D), as for the other solvents previously studied (I_a to I_d, for H₂O, MeOH, MeCN). This changeover is shifted to the earlier elements of the series, due to more pronounced steric crowding for dimethylformamide hexasolvates.     

Thermochemistry of the Ternary Complex Nd（Et2dtc）3（phen）

Introduction A series of lanthanide sulfide complexes have beenlargely used for ceramics and thin film materials1 andthese complexes could be prepared from the precursorswhich are the compounds containing lanthanide-sulfurbonds.2-4 For instance, the compounds synthesized with[(alkyl)2dtc]-, phen?H2O and lanthanide salts were usedas the volatile precursors for preparing lanthanide sul-fide, its friction properties in lubricant was investigatedin literature 5 and the preparation and propertie…     

Properties of amorphous and crystallizable hydrocarbon polymers. I. Melt rheology of fractions of linear polyethylene

The dynamic moduli G′(ω) and G″(ω) for two groups of linear polyethylene fractions (reported M _w/M _n < 1.2) were measured in the melt state using the eccentric rotating disk method. Values of zero shear viscosity η₀ were obtained and compared with published results on similar fractions. Molecular weight data were converted to a common basis through intrinsic viscosities in trichlorobenzene (TCB) at 135°C. With recent data on M _w (light scattering) vs. [η]_TCB, for linear polyethylene, the relationship at 190°C, η₀ = 3.40 × 10^?14(M _w)^3.60, was obtained. The flow activation energy E_a was 6.4 kcal (T = 140–195°C). The plateau modulus G at 190°C was determined from the area under the loss modulus peak in one high-molecular-weight sample. The value obtained, G = 1.5₈ × 10⁷ dyn/cm², corresponds to an apparent molecular weight between entanglements of 1850. The storage compliance J′(ω) becomes anomalously large at low frequencies. The recoverable compliance J could not be determined for any of the fractions.     

Depolymerization kinetics of di(4‐tert‐butyl cyclohexyl) itaconate and Mark‐Houwink‐Kuhn‐Sakurada parameters of di(4‐tert‐butyl cyclohexyl) itaconate and di‐n‐butyl itaconate

Multipulse pulsed laser polymerization coupled with size exclusion chromatography (MP‐PLP‐SEC) has been employed to study the depropagation kinetics of the sterically demanding 1,1‐disubstituted monomer di(4‐tert‐butylcyclohexyl) itaconate (DBCHI). The effective rate coefficient of propagation, k, was determined for a solution of monomer in anisole at concentrations, c, 0.72 and 0.88 mol L^?1 in the temperature range 0 ≤ T ≤ 70 °C. The resulting Arrhenius plot (i.e., ln k vs. 1/RT) displayed a subtle curvature in the higher temperature regime and was analyzed in the linear part to yield the activation parameters of the forward reaction. In the temperature region where no depropagation was observed (0 ≤ T ≤ 50 °C), the following Arrhenius parameters for k_p were obtained (DBCHI, E_p = 35.5 ± 1.2 kJ mol^?1, ln A_p = 14.8 ± 0.5 L mol^?1 s^?1). In addition, the k data was analyzed in the depropagatation regime for DBCHI, resulting in estimates for the associated entropy (?ΔS = 150 J mol^?1 K^?1) of polymerization. With decreasing monomer concentration and increasing temperature, it is increasingly more difficult to obtain well structured molecular weight distributions. The Mark Houwink Kuhn Sakurada (MHKS) parameters for di‐n‐butyl itaconate (DBI) and DBCHI were determined using a triple detection GPC system incorporating online viscometry and multi‐angle laser light scattering in THF at 40 °C. The MHKS for poly‐DBI and poly‐DBCHI in the molecular weight range 35–256 kDa and 36.5–250 kDa, respectively, were determined to be K_DBI = 24.9 (10³ mL g^?1), α_DBI = 0.58, K_DBCHI = 12.8 (10³ mL g^?1), and α_DBCHI = 0.63. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1931–1943, 2007