A Novel Fiber with Phenyl-Functionalized MSU (Michigan State University) Coating for Solid-Phase Microextraction Combined with High Performance Liquid Chromatography for Preconcentration and Determination of Trace Polychlorinated Biphenyls in Environmental Water Samples

A novel and robust phenyl-functionalized MSU-1 (Ph-MSU) coated fiber for solid-phase microextraction (SPME) coupled to high performance liquid chromatography (HPLC) was developed for the preconcentration and the determination of 2,4,4′-trichlorobiphenyl (PCB 28), 2,4′,5-trichlorobiphenyl (PCB 31), 2,2′,5,5′-tetrachlorobiphenyl (PCB 52), 2,2′,4,5,5′-pentachlorobiphenyl (PCB 101), 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118), 2,2′,3,4,4′,5′-hexachlorobiphenyl (PCB 138), 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153), and 2,2′,3,4,4′,5,5′-heptachlorobiphenyl (PCB 180) in environmental water samples. Experimental conditions affecting SPME were examined in detail. The Ph-MSU coating provided large porosity and short-range mesostructures necessary for high extraction capacity and rapid mass transfer of PCBs. The Ph-MSU coated fiber exhibited selectivity for PCB 28, PCB 31, PCB 118, and PCB 138 in a limited extraction time. Good linearity for all PCBs was obtained with correlation coefficients from 0.9987 to 0.9994. The recoveries were within 94.3% to 103% for the spiked water with 300 ng · L^?1 per PCB. The relative standard deviations (RSDs) ranged from 3.10% to 6.23% and the limits of detection (LODs) were between 8.73 ng · L^?1 and 13.8 ng · L^?1. The proposed method was applied for the determination of PCBs in real river water and rainwater samples. The median recoveries ranged from 85.6% to 118% with RSDs between 4.23% and 8.78%. The experimental results demonstrated that the Ph-MSU fiber coating could be reused for over 250 times without loss of the extraction efficiency. These results clearly indicate that the Ph-MSU coated fiber was rapid, sensitive, and suitable for the preconcentration and determination of trace PCBs in environmental water samples.     

Vapour pressure of α-iodonaphthalene

Using three different techniques, the vapour pressure of α-iodonaphthalene was measured in the temperature range 322–422 K. The pressure equation log P(kPa) = 8.82 ± 0.29 ? (3719 ± 300) /T, was determined. The enthalpy of vaporization change, ΔH⁰₂₉₈ = 69.4 ± 4.0 kJ mole^?1, was determined as the average of the results obtained by second-and third-law treatment of the experimental data. Antoine's constants, A = 6.258, B = 2010 and C = 171, were also derived.     

Thermodynamic properties of benzoylferrocene and 1,1′-dibenzoylferrocene

The vapor pressures of benzoylferrocene and 1,1′-dibenzoylferrocene were measured by torsion-effusion technique. The following pressure-temperature equations were derived benzoylferrocene log P(kPa) = 10.75±0.22?(5314±82)/T 1,1′-dibenzoylferrocene log P(kPa) = 9.29±0.24?(4898±91 )/T Second-law treatment of the experimental data yielded the sublimation enthalpies for benzoylferrocene and 1,1′-dibenzoylferrocene: ΔH⁰_sub,298 = 116.3±6.0 kJ mole^?1 and ΔH⁰_sub,298 = 109.3±6.0 kJ mole^?1 respectively. Thermal functions of these compounds were also estimated.     

Vapor pressure measurements of ferrocene,mono- and 1,1′-di-acetyl ferrocene

By using different techniques the vapor pressure of ferrocene, mono-acetyl ferrocene and 1,1′-di-acetyl ferrocene was measured. The following pressure—temperature equations were derived ferrocene log P(kPa)= 9.78 ± 0.14 ? (3805 ± 46)/T mono-acetyl ferrocene log P(kPa) = 14.83 ± 0.14 ? (5916 ± 48)/T 1,1′-di-acetyl ferrocene log P(kPa) = 8.82 ± 0.11 ? (4289 ± 44)/T By second- and third-law treatment of the vapor data the ΔH⁰_sub,298 = 74.0 ± 2.0 kJ mole^?1 for the sublimation process of ferrocene was calculated and compared with the literature data. For the sublimation enthalpy of mono- and 1,1′-di-acetyl ferrocene the values ΔH⁰_sub,298 = 115.6 ± 2.5 kJ mole^?1 and ΔH⁰_sub,298 = 91.9 ± 2.5 kJ mole^?1 were derived by second-law treatment. Thermal functions of these compounds were also estimated.     

Thermal analysis of 5′-deoxy-5′-iodo-2′,3′-O-isopropylidene-5-fluorouridine

The melting temperature, melting enthalpy, and specific heat capacities (C _p) of 5′-deoxy-5′-iodo-2′,3′-O-isopropylidene-5-fluorouridine (DIOIPF) were measured using DSC-60 Differential Scanning Calorimetry. The melting temperature and melting enthalpy were obtained to be 453.80 K and 33.22 J g^?1, respectively. The relationship between the specific heat capacity and temperature was obtained to be C _p/J g^?1 K^?1 = 2.0261 – 0.0096T + 2 × 10^?5 T ² at the temperature range from 320.15 to 430.15 K. The thermal decomposition process was studied by the TG–DTA analyzer. The results showed that the thermal decomposition temperature of DIOIPF was above 487.84 K, and the decomposition process can be divided into three stages: the first stage is the decomposition of impurities, the mass loss in the second stage may be the sublimation of iodine and thermal decomposition process of the side-group C₄H₂O₂N₂F, and the third stage may be the thermal decomposition process of both the groups –CH₃ and –CH₂OCH₂–. The obtained thermodynamic basic data are helpful for exploiting new synthetic method, engineering design, and commercial process of DIOIPF.     

Nucleation and crystal growth in Na2O · 2 CaO · 3 SiO2 glass: a DTA study

The non-isothermal devitrification of Na₂O · 2 CaO · 3 SiO₂ glass has been studied by differential thermal analysis in order to evaluate, from DTA curves, the temperature of maximum nucleation rate, T_m, and the activation energy values, E_c, for crystal growth.The temperature, T_m=580°C, is very close to the glass transition temperature, T_g=570°C, and the value of E_c=78 Kcal mole^?1 for the surface crystal growth is nearly the same as the value E_c=89 kcal mole^?1 for the bulk crystal growth; both are consistent with the activation energy for viscous flow. It is also pointed out that the nucleation rate—temperature curve and the crystallization rate—temperature curve are partially overlapped.     

Thermodynamics of solid solution formation in NiOMgO and NiOZnO

High-temperature calorimetric measurements of the enthalpies of solution in molten 2PbO · B₂O₃ of (Ni_xMg_1?x)O and (Ni_xZn_1?x)O permit the calculation of the enthalpy of the zincite to rocksalt transformation in ZnO, and the enthalpies of mixing, relative to rocksalt standard states, in the two solid solution series. The enthalpy of the zincite to rocksalt transformation is 24,488 ± 3,592 J mole^?1 with a corresponding positive entropy change of 0.48 ± 3.3 J K^?1 mole^?1. The small positive entropy change for the transformation necessitates a very flat and perhaps negative $\text{dP}\text{dT}$ slope for the phase boundary. Both solid solutions, when referred to rocksalt standard states, show negative enthalpies of mixing. For (Ni_xMg_1?x)O the negative enthalpies of mixing are fitted by a subregular model, where ΔH_mix = X_AX_B(BX_A + AX_B), with A = ?21,971 ± 4,953 J mole^?1 and B = ?5103 ± 1151 J mole^?1. The associated negative excess entropies of mixing, calculated from the heats of mixing and previously measured activity-composition relations, are similarly modeled with A = ?10.7 J K^?1 mole^?1 and B = + 1.1 J K^?1 mole^?1. Negative enthalpies of mixing in (Ni_xZn_1?x)O conform to a regular solution model with W = ?13520 ± 5581 J mole^?1. The negative enthalpies of mixing are interpreted in terms of a tendency toward ordering in the solid solutions, the proposed ordering scheme finding support in spectroscopic, structural, and magnetic data. These tendencies toward order are used to explain observed phase relations and thermodynamic properties in some other systems containing a transition metal cation and another ion of similar size, namely carbonates, hydrated sulfates and the systems CuOMO (M = Mg, Co, Ni).     

Über einen neuen Typ der Lysolecithin-Acylierung

A new Batch microcalorimeter was employed to investigate the existence of a relationship between the heat evolved during lecithin hydrolysis with phospholipase A (EC 3.1.1.4.) and the reversibility of the reaction. Factors, which allow the reacylation of lysolecithin, give rise to ΔH =?0.39 kcal · mole^?1 during the hydrolysis of lecithin. Whereas, a strongly exothermic reaction results either with desoxycholate (ΔH =?8.85 kcal · mole^?1) or with be venom phospholipase A (ΔH =?5.04 kcal · mole^?1) in the reaction system. The applied microcalorimetric method is fully described.     

Kinetics of the dissociation and cis-trans isomerization of o,o'-azodioxytoluene (dimeric o-nitrosotoluene)

The dimer-monomer reactions were investigated for the system cis and transo,o'-azodioxytoluene-o-nitrosotoluene in acetonitrile solvent. For the reaction cis dimer-monomer the following thermodynamic and activation parameters have been derived: ΔH°=58.5±2.5 kJ mole^?1, ΔS°=206.2±3.8 J mole^?1 K^?1, ΔH^≠=63.6±3.3 kJ mole^?1, ΔS^≠=6.3±0.3 J mole^?1 K^?1. The corresponding values for the reaction trans dimer-monomer are: ΔH°=45.6±2.1 kJ mole^?1, ΔS°=162.7±7.1 J mole^?1 K^?1, ΔH^≠=80.8±2.9 kj mole^?1, ΔS^≠=-13.4±0.8 mole^?1 K^?1. There is no evidence of a direct cis-trans isomerization (i.e. a reaction not proceeding via the monomer). NMR and various perturbation techniques monitoring the visible absorption of the monomer were employed.     

Fully imidized soluble polyimides based on a novel dianhydride: 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride

We have synthesized a novel dianhydride, 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride (DCBTDA). Polyimides were synthesized with DCBTDA or 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and several relatively rigid meta- and para- substituted mononuclear diamines. The BTDA based systems were insoluble in dipolar, aprotic solvents whereas the DCBTDA based polymers displayed enhanced solubility in these solvents. The thermal stability of these polyimides was excellent as measured by 5% weight loss decomposition. The T_g's of the polymers were all above 290°C.     

Poor hydration enhances the activation energy of the exchange rate of the base-paired imino protons with water at the core part of the DNA duplex

Here we report the exchange rates (k_{e x}) of imino protons of d[^5′p(T¹G²T³T⁴T⁵G⁶G⁷C⁸)^3′]:d[^{3∼'(A15C14A13A12A11C10C9)p5′}] (duplex I) with water at different pH and temperature to give the life-times (τ_o) of the closed state of the base-pairs. The τ_o of the closed state of the base-pairs is uniform (E_a ≈ 25 ± 5 kcal/mol) in the duplex I, and varies between 0.2 – 4 ms. A plot of the natural log of various exchange rates of the imino protons of the base-pair of the duplex I within the pH range of 6.1 to 8.6 as a function of the inverse of temperature gave the activation energy (E_a) of the exchange process of imino protons with the bound water (hydration). It has been found that although τ_o are in the same range but the E_a of the exchange processes of the open state of imino protons with the bound water are very different, and they are strongly dependent upon the location of the nucleotide residues along the DNA duplex: 22.3±3.3 kcal/mol for the core base-pair T⁴-A¹², 16.2±2.4 kcal/mol for the base-pair T⁵-A¹¹, 10.5±1.6 kcal/mol for the base-pair T³-A¹³. 12.3±1.8 kcal/mol for the base-pair G⁶-C¹⁰ and 2.4±0.4 kcal/mol for the base-pair G²-C¹⁴. The comparison of the activation energies of the exchange process of imino protons and water with that of the water abundance in the first spine of hydration between fully-matched duplex I and the analogous G⁷-A⁹ mismatched duplex II, (d[^5′p(T¹G²T³T⁴T⁵G⁶G⁷C⁸)^3′]: d[^3′(A¹⁵C¹⁴A¹³A¹²A¹¹C¹⁰A⁹)p^5′], determined by a combination of NOESY and ROESY experiments, suggests for the first time that the relative exchange of imino protons of the base-pairs in the DNA duplex is more rapid when there is an abundance of water at the first spine of hydration. This result also showed unambiguously that the core of the DNA is by and large devoid of water and the energy penalty of water entering the core is very high. This is consistent with our earlier work which showed that as the water activity in the minor and major groove of DNA increases, the T_m decreases (ref. 1), suggesting the water poisoning as the principal factor for base-pair mismatch, frame-shift and mutation in our DNA replication machinery.     

Tetra­methyl­ammonium pentaborate 0.25‐hydrate

The title compound, tetramethylammonium 4,4′,6,6′‐tetrahydroxy‐2,2′‐spirobi(cyclotriboroxane) 0.25‐hydrate, C₄H₁₂N⁺·B₅H₄O₁₀⁻·0.25H₂O, was synthesized under mild solvothermal conditions. The B₅O₆(OH)₄⁻ clusters are connected by strong hydrogen‐bonding interactions into a three‐dimensional structure containing rectangular channels along the a axis, in which the C₄H₁₂N⁺ ions and water mol­ecules are located.     

Estimation of Critical Temperature of Thermal Explosion for Nitrosubstituted Azetidines Using Non-isothermal DSC

Based on reasonable hypothesis, two general expressions and their six derived formulae for estimating the critical temperature (T_b) of thermal explosion for energetic materials (EM) were derived from the Semenov's thermal explosion theory and eight non‐isothermal kinetic equations. We can easily obtain the values of the initial temperature (T_0i) at which DSC curve deviates from the baseline of the non‐isothermal DSC curve of EM, the onset temperature (T_ei), the exothermic decomposition reaction kinetic parameters and the values of T₀₀ and T_e0 from the equation T_{0i or ei}=T_{00 or e0}+a₁β_i+a₂β_i²+···+a_L?2β_i^L?2, i=1, 2, ;···, L and then calculate the values of T_b by the six derived formulae. The T_b values for seven nitrosubstituted azetidines, 3,3‐dinitroazetidinium nitrate ( 1 ), 3,3‐dinitroazetidinium picrate ( 2 ), 3,3‐dinitroazetidinium‐3‐nitro‐1,2,4‐triazol‐5‐onate ( 3 ), 1,3‐bis(3′,3′‐dinitroazetidine group)‐2,2‐dinitropropane ( 4 ), 1‐(2′,2′,2′‐trinitroethyl)‐3,3‐dinitroazetidine ( 5 ), 3,3‐dinitroazetidinium perchlorate ( 6 ) and 1‐(3′,3′‐dinitroazetidineyl)‐2,2‐dinitropropane ( 7 ), obtained with the six derived formulae are agreeable to each other, whose differences are within 1.5%. The results indicate that the heat‐resistance stability of the seven nitrosubstituted azetidines decreases in the order 6 > 7 > 5 > 4 > 3 > 2 > 1 .     

Etude cinetique de la polymerisation cationique du cyclopentadiene amorcee par l'hexachloroantimoniate de triphenylmethyle

A study of cyclopentadiene polymerization, initiated by φ₃C⁺SbCl₆^? in methylene chloride solution, has been carried out at temperatures between ?70 and +20° using a dilatometric method. An overall external second order with respect to monomer has been found. At very low temperature (?70°), the concentration of active centres remains low and roughly constant, in agreement with a quasi-stationary state assumption. Between ?50 and + 10°, experimental determination of (k_p. M^*), obtained from variation of v_p and [M] with time, shows that the concentration of centres goes through a maximum, sharper and more rapidly reached as the temperature is raised. Initiation is slower than propagation and active centres are rapidly destroyed when termination becomes faster than initiation. This explains the partial conversions and the observed maximum for concentration of active centres. Propagation and unimolecular termination rate constants have been determined at each temperature: activation energies are E_p = ?8 ± 0·5 kcal mole^?1 and E_p = ?0·3 ± 0·1 kcal mole^?1. These negative values can be explained by an exothermic process of solvation of active centres, leading to more reactive propagating species.     

Chemiluminescence and catalysis of decomposition of dispiro(diadamantane-1,2-dioxetane) in the presence of EuIII and TbIII tris(benzoyltrifluoroacetonate) complexes

Catalysis of decomposition of dispiro(diadamantane-1,2-dioxetane) (1) in the presence of Eu^III and Tb^III tris(benzoyltrifluoroacetonate) complexes (Ln(btfa)₃) accompanied by the formation of adamantanone (2) and chemiluminescence (CL) was studied. The rate constants (k ₂) of decomposition of compound1 in the1·Ln(btfa)₃ complexes and their stability constants (K ₁) have been determined. The Arrhenius parameters of decomposition of1 (E _a= 22.4±0.7 kcal mol^?1, logA=10.2±0.8 for1·Tb(btfa)₃ andE _a=23.4±0.6 kcal mol^?1, logA=10.6±0.8 for1·Eu(btfa)₃) and thermodynamic parameters of complex formation (ΔH=?5.5±0.5 kcal mol^?1, ΔS=?10.4±0.7 e.u. for1·Tb(btfa)₃ and ΔH=?5.8±0.5 kcal mol^?1, ΔS=?10.9±0.7 e.u. for1·Eu(btfa)₃) have been calculated from the temperature dependences ofk ₂ andK ₁. The yields of excitation of the Ln(btfa)₃ chelates φ _Eu ^* =0.021±0.006 and φ _Tb ^* =0.12±0.04 have been determined. A higher efficiency of the occupation of the⁵D₄-level of Tb³⁺ compared to those of the⁵D₁- and⁵D₀-levels of Eu³⁺ is caused by different efficiencies of the non-radiative energy dissipation in the Ln³⁺ ion after the intracomplex energy transfer from the³n,π^*-state of2 to the resonance excited levels of lanthanides.     

Microwave spectrum of 3-nitrothiophene

The microwave spectrum of 3-nitrothiophene has been studied in the frequency region 26.5–40.0 GHz. The rotational transitions of the ground state and the first six torsionally excited states have been assigned. The ground state rotational constants have been determined to be A_o=4622.61 ± 0.07 MHz, B_o = 1231.751 ± 0.001 MHz and C_o = 973.062 ± 0.001 MHz. The planarity of the molecule has been demonstrated. The first torsional frequency and the barrier to internal rotation of the nitro group have been estimated as 60 cm^?1 and 3.8 kcal/mole, respectively.     

Zur Thermochemie der Verbindung Ba(NO3)2·2 KNO3

From the heats of solution for Ba(NO₃)₂ (c), KNO₃ (c; II), and Ba(NO₃)₂ · 2 KNO₃ (c) the heat of combination of the double salt from its component salts ΔH ₂₉₈ ⁰ =(?2.168±0.028) kcal · mole^?1 and the standard heat of formation ΔH _f,298 ⁰ =?474.75 kcal · mole^?1 have been determined. The values of derived thermodynamic properties are summarized in table 4.     

1，1－二氨基2，2－二硝基乙烯（DADE）的热化学性质、热行为和热分解机理

The constant-volume combustion energy, △cU （DADE, s, 298.15 K）, the thermal behavior, and kinetics and mechanism of the exothermic decomposition reaction of 1,1-diamino-2,2-dinitroethylene （DADE） have been investigated by a precise rotating bomb calorimeter, TG-DTG, DSC, rapid-scan fourier transform infrared （RSFT-IR） spectroscopy and T-jump/FTIR, respectively. The value of △cHm （DADE, s, 298.15 K） was determined as （-8518.09±4.59） j·g^-1. Its standard enthalpy of combustion, △cU （DADE, s, 298.15 K）, and standard enthalpy of formation, △fHm （DADE, s, 298.15 K） were calculated to be （-1254.00±0.68） and （- 103.98±0.73） kJ·mol^-1, respectively The kinetic parameters （the apparent activation energy Ea and pre-exponential factor A） of the first exothermic decomposition reaction in a temperature-programmed mode obtained by Kissinger＇s method and Ozawa＇s method, were Ek=344.35 kJ·mol^-1, AR= 1034.50 S^-1 and Eo=335.32 kJ·mol^-1, respectively. The critical temperatures of thermal explosion of DADE were 206.98 and 207.08 ℃ by different methods. Information was obtained on its thermolysis detected by RSFT-IR and T-jump/FTIR.     

An oxidovanadium(IV) complex having a perrhenato ligand: An efficient catalyst for aerobic oxidation reactions of benzylic and propargylic alcohols

An oxidovanadium(IV) complex having a perrhenato ligand [VO(ReO₄)(4,4′-^tBubpy)₂][0.25SO₄·0.5ReO₄] (4,4′-^tBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine) efficiently catalyzes not only dehydrogenative oxidation of benzylic and propargylic mono-alcohols but also oxidative CC bond cleavage of meso-1,2-diaryl-1,2-ethanediols under atmospheric molecular oxygen, affording the corresponding carbonyl compounds in good yield.     

Data on the thermochemistry of azoalkanes

The rate constant of the primary decomposition step was determined for four symmetrical and four unsymmetrical azoalkanes. From the experimental activation energies and some literature enthalpy data, the following enthalpies of formation of radicals and group contributions were calculated: ΔH_? (CH₃N₂) = 51.5 ± 1.8 kcal mol^?1, ΔH_? (C₂H₅N₂) = 44.8 ± 2.5 kcal mol^?1, ΔH_? (2?C₃H₇N₂) = 37.9 ± 2.2 kcal mol^?1, [N_A-(C)] = 27.6 ± 3.7 kcal mol^?1, [N_A-(?_A) (C)] = 61.2 ± 3.1 kcal mol^?1.