共查询到20条相似文献,搜索用时 31 毫秒
1.
The compounds [MBr 2( p-clan) 2] (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II); p-clan = 4-chloroaniline) were synthesized and characterized by melting points, elemental analysis, thermal analysis and electronic and IR spectroscopy. The enthalpies of solution of the adducts, metal(II) bromides and 4-chloroaniline in methanol, 1.2 M aqueous HCl or 25% (v/v) 1.2 M aqueous HCl in methanol were measures and by using thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reactions (Δ rH°), the standard enthalpies of formation (Δ fH°), the standard enthalpies of decomposition (Δ DH°), the lattice standard enthalpies (Δ MH°) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Δ rH°(g)). The mean bond dissociation enthalpies of the metal(II)-nitrogen coordinated bonds and the enthalpies of adduct formation in the gaseous phase have been estimated. 相似文献
2.
The enthalpies of dissolution in water of new ternary complexes of four late trivalent lanthanide ions Ln(Gly) 4Im(ClO 4) 3· nH 2O (Ln=Gd, Tb, Dy, Y; Gly: glycine; Im: imidazole and n=1 or 2) were measured by means of a Calvet microcalorimeter. Empirical formulae for the calculation of the enthalpies of dissolution (Δ dissH), relative apparent molar enthalpies (Δ dissH (app)), relative partial molar enthalpies (Δ dissH (partial)) and enthalpies of dilution (Δ dilH1,2) were obtained from the experimental data of the enthalpies of dissolution of these complexes. The plot of Δ dissHmΘ, Δ dissH (app) and Δ dissH (partial) versus the values of the ionic radius of the lanthanide element ( r) showed a grouping effect of the lanthanide elements, indicating that the coordinated bond between the lanthanide ions and the ligands has some covalent character. The unknown value of the standard enthalpy of dissolution for the similar complex: Ho(Gly) 4Im(ClO 4) 3·H 2O was estimated according to the plot of Δ dissHmΘ versus r. 相似文献
3.
The effect of temperature on the extraction of FE(III) by dehydrated castor oil fatty acids (DCOFA) has been studied in the temperature range 283–313 K at 1.0 M constant ionic strength (NaClO 4). The temperature dependence of the conditional constant of extraction is given in the form: ln K ext=31.95 − 12800(1/ T). Also, it was found that the average thermodynamic parameters, Δ H° ext, Δ G° ext, and Δ S° ext are 106.5 kJ/mole, 27.3 kJ/mole, and 0.3 kJ. mole −1.K −1, respectively. The extracted species in toluene solution were identified as FeR 3.HR and Fe(OH)R 2, where HR represents the fatty acid used. 相似文献
4.
The complexation reactions between murexide and Co 2+, Ni 2+ and Cu 2+ in C 2H 5OH-H 2O mixtures have been investigated spectrophotometrically. The formation constants of the 1:1 complexes formed increase in the order Co 2+ < Ni 2+ < Cu 2+ for all solvent mixtures studied, and log Kf is a linear function of the mole fraction of ethanol. The heat of complexation was determined calorimetrically for the nickel and copper complexes. The values of Δ H° and Δ S° are solvent-dependent, and all three complexes have negative Δ H° and positive Δ S° values. 相似文献
5.
Induced ferroelectric S* C phases are formed by non-chiral S C host phases doped with chiral dipolar guest molecules. In those mixtures the spontaneous polarization Ps and the tilt angle Θ has been investigated as a function of the mole fraction xG of the chiral dopant. In most cases the reduced polarization P0 = PS/ sin Θ has been found to depend linearly on xG. The polarization power which is defined by δP=(∂ P0/∂ xG)Δ T is discussed in terms of the molecular structure of the chiral dopants. There are systems in which P0( xG) deviates positively from linearity. This behaviour can be understood by considering a local field correction to P0. By assuming a local field of Lorentz type a theoretical relation for P0( xG) has been derived which explains the experimental results. The effect of a local field is considerable if the transverse dipole moment and the polarizability of the chiral dopant are large. 相似文献
6.
Activities of solutes and compositions of solutions may be expressed corretly in terms of molarity ( c), molality ( m) or mole fraction ( x), leading to corresponding equilibrium constants Kc, Km, or Kx. Equations for differences between Δ G° c, Δ G° m, and Δ G° x values are derived. Common errors in calculations involving (dln Kc/d T) and (dln Kc/d P) are identified and remedies for these errors are presented. 相似文献
7.
Lamellar crystalline calcium phenylphosphonate, as anhydrous Ca(HO 3PC 6H 5) 2 and hydrated Ca(HO 3PC 6H 5) 2·2H 2O compounds, were used as hosts for intercalation of polar n-alkylmonoamine molecules of the general formula CH 3(CH 2) nNH 2 ( n=0–4, 7) in water or 1,2-dichloroethane. An increase in the interlayer distance was observed. The exothermic enthalpic values for intercalation increased with the number of carbon atoms and with increasing concentration of the amines. The intercalation followed by a titration procedure in the solid/liquid interface with Ca(HO 3PC 6H 5) 2·2H 2O and Ca(HO 3PC 6H 5) 2 gave the enthalpy/number of carbons correlations: Δ intH=−(1.74±0.43)–(1.30±0.13) nc and Δ intH=−(4.15±0.15)–(1.07±0.03) nc, for water and 1,2-dichloroethane, respectively. A similar correlation Δ intH=−(4.27±0.80)–(1.85±0.21) nc was obtained in water by using the ampoule breaking procedure for Ca(HO 3PC 6H 5) 2·2H 2O. The increase in exothermic enthalpic values with the increase in n-aliphatic carbon atoms is more pronounced for the anhydrous compound and also when using the ampoule breaking procedure. The Gibbs free energies are negative. Positive entropic values favor intercalation in these systems. 相似文献
8.
A calorimetric study was performed for adducts of general formula CdBr 2· nL ( n=1 and 2; L=ethyleneurea (eu) and propyleneurea (pu)). The standard molar reaction enthalpy in condensed phase: CdBr 2(c)+ nL(c)=CdBr 2· nL(c); Δ rHmθ, were obtained by reaction–solution calorimetry, to give the following values for mono- and bis-adducts: −19.54 and −34.59; −7.77 and −19.05 kJ mol −1 for eu and pu adducts, respectively. Decomposition (Δ DHmθ) and lattice (Δ MHmθ) enthalpies, as well as the mean cadmium---oxygen bond dissociation enthalpy, DCd---O, were calculated for all adducts. 相似文献
9.
Excess molar enthalpies HE and excess molar volumes VE have been measured, as a function of mole fraction x1, at 298.15 K and atmospheric pressure for the five liquid mixtures ( x11,4-C 6H 4F 2 + x2n-C lH 2l+2), l = 7, 8, 10, 12 and 16. In addition, HE and excess molar heat capacities CPE at constant pressure have been determined for the two liquid mixtures ( x1C 6F 6 + x2n-C lH 2l+2), l = 7 and 14, at the same temperature and pressure. The instruments used were flow microcalorimeters of the Picker design (the HE version was equipped with separators) and a vibrating-tube densimeter, respectively. The excess enthalpies of the five difluorobenzene mixtures are all positive and quite large; they increase with increasing chain length l of the n-alkane from HE(x1 = 0.5)/(J mol−1) = 1050 for l = 7 to 1359 for l = 16. The corresponding excess volumes VE are all positive and also increase with increasing l: VE(x1 = 0.5)/(cm3 mol−1) = 0.650 for l = 7 and 1.080 for l = 16. Interestingly, the excess enthalphies of the corresponding mixtures with hexafluorobenzene are only about 5% larger, whereas the excess volumes of (x1C6F6 + x2n-ClH2l+2) are roughly twice as large as those of their counterparts in the series containing 1,4-C6H4F2. Specifically, at 298.15 K HE(x1 = 0.5)/(J mol−1) = 1119 for (x1C6F6 + x2n-C7H16) and 1324 for (x1C6F6 + x2n-C14H30), and for the same mixtures VE(x1 = 0.5)/(cm3 mol−1) = 1.882 and 2.093, respectively. The excess heat capacities for both systems are negative and of about the same magnitude as the excess heat capacities of mixtures of fluorobenzene with the same n-alkanes (Roux et al., 1984): CPE(x1 = 0.5)/(J K−1 mol−1) = −1.18 for (x1C6F6 + x2n-C7H16), and −2.25 for (x1C6F6 + x2n-C14H30). The curve CPE vs. (x1 for x1C6F6 + x2n-C14H30) shows a sort of “hump” for x1 0.5, which is presumed to indicate emerging W-shape composition dependence at lower temperatures. 相似文献
10.
Anion exchange membrane has been investigated in different electrolyte solutions by chronopotentiometry to explore the influence of co-ion and counterion of the exchange group of the membrane, on the transport phenomena. Chloride, nitrate, sulfate and acetate in sodium salts were used as counterions and sodium, potassium, calcium and ammonium in chloride salts were used as co-ions. The membrane showed a potential drop ( E0) in all these electrolytes when a constant current was applied across it, which remained constant for a period less than τ, called the transition time and rose gradually to a maximum ( Emax) value. The parameters such as τ, E0 and Emax and the potential jump (Δ E) and τ and the inflection zone (Δ t) along the time axis have been measured and compared at an applied current density ( I) of 10 mA cm −2 in 10 mM solutions. The values of τ1/2/ zA[ A0] or τ1/2/ zC[ C0], with
or
, E0 and Δ E with
or
(where rA and rC are the ionic radii of counter and co-ions, respectively) have been correlated. Permselectivity ( P) and transference number
of the membrane with respect to each one of the above electrolytes have been evaluated and discussed. 相似文献
11.
The e.m.f. of the galvanic cells Pt,C,Te(l),NiTeO 3,NiO/15 YSZ/O 2 ( Po2 = 0.21 atm),Pt and Pt,C,NiTeO 3,Ni 3TeO 6,NiO/15 YSZ/O 2 ( Po2 = 0.21 atm),Pt (where 15 YSZ=15 mass% yttria-stabilized zirconia) was measured over the ranges 833–1104 K and 624–964 K respectively, and could be represented by the least-squares expressions E(1)±1.48 (mV) = 888.72 − 0.504277 (K) and E(II) ±4.21 (mV) = 895.26 − 0.81543 T (K). After correcting for the standard state of oxygen in the air reference electrode, and by combining with the standard Gibbs energies of formation of NiO and TeO2 from the literature, the following expressions could be derived for the ΔG°f of NiTeO3 and Ni3TeO6: ΔGf°(NiTeO3) ± 2.03 (kJ mol−1) = −577.30 + 0.26692T (K) and ΔG°f(Ni3TeO6)±2.54 (kJ mol−1) = −1218.66 + 0.58837T (K). 相似文献
12.
The heat capacity of copper hydride has been measured in the temperature range 2–60 and 60–250 K using two adiabatic calorimeters. Special procedure for the purification of CuH has been applied and a careful analysis of sample contamination has been performed. The experimental results have been extrapolated up to 300 K due to instability of the copper hydride at room temperature. From the temperature dependence of heat capacity the values of entropy S°( T), thermal part of enthalpy H°( T)− H°(0) and Gibbs function [−( G°( T)− H°(0))] have been calculated assuming S°(0)=0. The standard absolute entropy, standard entropy of formation from the elements and enthalpy of decomposition of copper hydride from the elements have been calculated and found to be 130.8 J K −1 mol −1 (H 2), −85.1 J K −1 mol −1 (H 2), −55.1 kJ mol −1 (H 2), respectively. These new results gave the possibility of discussion on thermodynamic properties of copper hydride. Debye temperature has been for the first time determined experimentally. 相似文献
13.
The influence of the –NH 2 group position in the pyridine ring on the proton donor ability of N–H groups in hydrogen bonding as well as on the spectral behaviour of stretching and bending vibrations of aminopyridines has been studied. The proton donor ability was shown to increase in the row: meta-, ortho-, and para-aminopyridines. It was established tha N–H bonds in ortho-aminopyridine were not equivalent, and the evaluation of their dynamic nonequivalence was made. The influence of temperature on the spectral characteristics of the absorption bands of the stretching vibrations of amine groups in the free and hydrogen bonded molecules in CCl4 has been studied (in temperature range 290–330 K), the formation constants of the complexes have been determined, enthalpy of the 1:1 complexes formation (−ΔH1) between ortho- and meta-aminopyridines with dimethylformamide, dimethylsulphoxide and hexamethylphosphoramide has been calculated in temperature range 290–330 K. The 1:2 complexes of ortho-, meta- and para-aminopyridines with acetonitrile, tetrahydrofurane, dimethylsulphoxide, hexamethylphosphoramide were studied at the indoor temperature. Enthalpy of the 1:2 complex (−ΔH2) was estimated on the basis of ‘intensity rule’; −ΔH1=ΔB1/2 assuming that parameter does not depend on the composition of a complex. The vibrational and electrooptical tasks were solved for the free and H-bounded molecules of aminopyridines as well as its complexes of the 1:1 and 1:2 compositions. Dynamic, electrooptical and energetic nonequivalency of NH bonds of aminogroups in aminopyridines was studied quantitatively. The independent calculations of dynamic constants proved mentioned above nonequivalency of NH bonds. Correlations between spectral characteristics of the absorption bands, geometric, dynamic and electrooptical parameters of –NH2 group in aminopyridines in the free and hydrogen bonded molecules have been established. Those correlations allow to determine the most important molecular characteristics obtained on the basis of spectral measurements in the range of the absorption bands of the stretching vibrations of aminogroup. 相似文献
14.
The rate coefficients of the reactions: (1) CN + H 2CO → products and (2) NCO + H 2CO → products in the temperature range 294–769 K have been determined by means of the laser photolysis-laser induced fluorescence technique. Our measurements show that reaction (1) is rapid: k1(294 K) = (1.64 ± 0.25) x 10 −11 cm 3 molecule −1 s −1; the Arrhenius relation was determined as k1 = (6.7 ± 1.0) x 10 −11 exp[(−412 ± 20)/T] cm 3 molecule −1 s −1. Reaction (2) is approximately a tenth as rapid as reaction (1) and the temperature dependence of k2 does not conform to the Arrhenius form: k2 = 4.62 x 10 −17T1.71 exp(198/ T) cm 3 molecule −1 s −1. Our values are in reasonable agreement with the only reported measurement of k1; the rate coefficients for reaction (2) have not been previously reported. 相似文献
15.
The Gibbs energy of formation of IrO 2(s) has been measured by means of oxygen dissociation pressure measurements, and by EMF measurements using ZrO 2 (+ CaO) as the solid electrolyte. In addition, high-temperature enthalpy increments of IrO 2 have ben measured from 416 to 940 K using a drop calorimeter. A “third law” evaluation of the experimental results and data from literature has been made. For the enthalpy of formation of IrO 2(s) the value Δ H° f (298.15 K) - −(59.60 ± 0.03) kcal mole −1 has been selected. The thermodynamic functions of IrO 2(s) have been calculated in the temperature range 298–1200 K. 相似文献
16.
The thermodynamic data (Δ G0, Δ H0 and TΔ S0) of the solvation of tetraphenylarsonium-tetraphenylborate (Ph 4AsPh 4B) and its neutral parts, tetraphenylgermanium (Ph 4Ge) and tetraphenylmethane (Ph 4C) in methanol— N,N-dimethylformamide mixed solvents are discussed. The values of the free energy of transfer, ΔsMG0, are calculated from measurements of the solubilities of Ph4AsPh4B, Ph4Ge and Ph4C in the successive fractions of MeOH in DMF at three different temperatures (15, 25, 35°C). The values of ΔsMH0 and TΔsMS0 for the derivatives are calculated from ΔsMG0 values. The values of ΔsMG0, ΔsMH0 and TΔsMS0 of tetraphenylarsonium and tetraphenylborate ions have also been carefully calculated. The ratios of ΔsMG0 values (ΔsMG0 = ΔG0(+)/ΔG0(−)) were found to be greater than unity. Similarly, the ratios of ΔsMH0 and TΔsMS0 for the positive and negative ions were found to be greater than unity. 相似文献
17.
Structures, energetics and vibrational frequencies of the interaction of adsorbates with H-aluminosilicates (H-AlZ), H-gallosilicates (H-GaZ), alkali-metal exchanged aluminosilicates (X-AlZ) and alkali-metal exchanged gallosilicates (X-GaZ), where X being Li, Na, or K, have been carried out at B3LYP and HF levels of theory with 6-31G(d) as the basis set. The charge compensating alkali-metal ions can affect the catalytically active site (Si–O–T where T=Al or Ga) by weakening the Si–O, Al–O, and Ga–O bonds as compared to their anionic frameworks. Comparing the net stabilization energies, Δ ENSE, of the naked alkali-metal/H 2O adducts with those of the alkali-metal exchanged zeolite/H 2O systems, the latter amounts only to about 50% of the former, which is partly due to the destabilizing role of the negative zeolitic oxygen frameworks surrounding the cations. The interaction of sorbates with the alkali-metal exchanged gallosilicates can be employed to probe the field strength inside the catalytic frameworks as indicated by the plot of the binding energy, Δ E, versus 1/ RX–Ow2, with R(X–Ow) being the distance between the cationic nucleus and the oxygen atom of the adsorbate. The IR spectra of H 2O adsorbed on Na-AlZ are calculated to be 3584, 3651, and 1686 cm −1. The obtained results are in excellent agreement with the very recent experimental IR spectra of water adsorbed on Na-ZSM-5 of Zecchina et al. (J. Phys. Chem., 100 (1996) 16 484). Other important features, i.e. the correlation between Δ νOH and, Δ E, R(X–Ow), and 1/ RX–Ow2, cationic size, demonstrate that the interactions of sorbates with alkali-metal exchanged gallosilicates are well approximated by electrostatic contribution. 相似文献
18.
The biamperometry for the direct determination of irreversible redox analytes in flow system has been proposed based on coupling two independent and irreversible couples to form the biamperometric detection scheme. In this work, the method is studied both theoretically and experimentally. Equations describing the current–voltage characteristics and the current–concentration relationship are presented. The influence of the applied potential difference (Δ E) and the half-wave potential difference (Δ E1/2) between two irreversible couples on the method are discussed. It shows that small Δ E1/2 is favorable to construct the biamperometric detection system and to achieve high sensitivity and selectivity. Increasing Δ E leads to an increase in sensitivity. This is, however, accompanied by a decrease in selectivity and signal-to-noise ratio. To construct the biamperometric scheme for the irreversible systems with large Δ E1/2, two approaches, adjusting acidity of supporting electroyte or adding new irreversible couple, are proposed by taking uric acid/platinum oxide and phenol/permanganate systems as examples. Uric acid and phenol are, respectively, detected in a flow injection system with a biamperometric detector. 相似文献
19.
The electrochemical behavior of adriblastina has been studied at in situ mercury film electrode (in situ MFE) and platinum electrode (PtE) in the presence of phosphoric acid as supporting electrolyte using Osteryoung square-wave stripping voltammetry (OSWSV) and cyclic voltammetry (CV). Optimal experimental and operational parameters have been selected for the drug accumulation and determination in aqueous medium. The interaction of the drug with single stranded DNA (ssDNA) has been studied and validated by using classical least square and partial least square with propagation of error. The formal potentials E° and E°′ and the equilibrium constants K1 and K2 have been calculated. It was found that K2 for the oxidized form of adriblastina is 63 times than K1 for the reduced form. Among several possible interfering metal ions, a complex formation reaction was observed between adriblastina and Cu(II) ions at in situ MFE. Cu(II) ions formed 1:2 metal:drug complex which is more stable than ssDNA–drug interaction and consequently it inhibits drug biochemical damage effects. The copper complex offers sub-nanograms determination of adriblastina in that 5.80 and 180 pg/ml could be easily detected in aqueous and urine media, respectively, with R.S.D. less than 4%. F-test and t-test have been applied in urine media giving good results that indicated the high accuracy of the proposed method. 相似文献
20.
The surface tension isotherms for pure oligooxypropylenated piperidine and morpholine at the aqueous solution—air interface were determined and interpreted. The surface excess concentration, Γ, the surface area per molecule, A, and the standard free energy of adsorption, Δ G°, were calculated according to a new empirical adsorption equation. The standard free energy contribution for the oxypropylene group (PO) in morpholine derivatives,Δ G° (PO) = −3.34 kJ mol −1, is substantially lower than that for the PO group located in the piperidine derivatives, i.e. Δ G° (PO)= −3.12 kJ mol −1. 相似文献
|