Excess enthalpies and excess volumes of 1-nitropropane +, and 2-nitro-propane +, each of several non-polar liquids

Excess molar enthalpies H_m^E and excess molar volumes V_m^E have been measured for xC₃H₇NO₂ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 and 318.15 K; +(1 ? x)C₆H₁₄ (V_m^E only) at 298.15 K; +(1 ? x)p-C₆H₄(CH₃)₂ at 298.15 K; and for xCH₃CH(NO₂)CH₃ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 K; +(1 ? x)C₆H₁₄ at 298.15 K; +(1 ? x)(CH₃)₂CHCH(CH₃)₂ for H_m^E at 318.15 K and for V_m^E at 298.15 K; and +(1 ? x)C₁₆H₃₄ at 298.15 K. The H_m^E′s were determined with an isothermal dilution calorimeter and the V_m^E′s with a continuous-dilution dilatometer. Particular attention was paid to the region dilute in nitroalkane. In general H_m^E is large and positive for (a nitropropane + an alkane), less positive for (a nitropropane + tetrachloromethane), and small for (a nitropropane + benzene) and for (a nitropropane + 1,4-dimethylbenzene). The mixture with hexadecane shows phase separation. V_m^E is large and positive for (1-nitropropane + cyclohexane), less positive for (1-nitropropane + hexane), and S-shaped for (1-nitropropane + tetrachloromethane) with negative values in the 1-nitropropane-rich region. For (1-nitropropane + benzene) and for (1-nitropropane + 1,4-dimethylbenzene) V_m^E is negative. For mixtures with 2-nitropropane the results are similar except that for benzene V_m^E is S-shaped with positive values in the 2-nitropropane-rich region.     

Excess functions of (an alkane + carbon disulphide) at 298.15 K

Vapour pressures, excess enthalpies, and densities for {(1?x)C₆H₁₄ + xCS₂} {(1?x)C₁₀H₂₂ + xCS₂}, {(1?x)C₁₃H₂₈ + xCS₂}, and {(1?x)C₁₆H₃₄ + xCS₂} have been measured at 298.15 K. It was found that H_m^E and V_m^E increase as chain length increases while G_m^E diminishes, becoming negative for hexadecane.     

Thermal studies and spectral characterization of the chelate of bis-(η5-cyclopentadienyl titanium(IV) with salicylidene-4-methylaniline

A new chelate (η⁵-C₅H₅)₂Ti(SB)₂, whereSB=O, N donor Schiff base salicylidene-4-methylaniline, was synthesized. The course of thermal degradation of the chelate was studied by thermogravimetric (TG) and differential thermal analysis (DTA) under dynamic conditions of temperature. The order of the thermal decomposition reaction and energy of activation was calculated from TG curve while from DTA curve the change in enthalpy was calculated. Evaluation of the kinetic parameters was performed by Coats-Redfern as well as Piloyan-Novikova methods which gaven=1, ΔH=1.114 kJ·mol^?1, ΔE=27.01 kJ·mol^?1, ΔS=?340.12 kJ·mol^?1·K^?1 andn=1, ΔH=1.114 kJ·mol^?1, ΔE=20.01 kJ·mol^?1, ΔS=?342.60 kJ·mol^?1·K^?1, respectively. The chelate was also characterized on the basis of different spectral studies viz. conductance, molecular weight, IR, UV-visible and¹H NMR, which enabled to propose an octahedral structure to the chelate.     

Effect of in impurity on crystallization kinetics of (Se.7Te.3)100−xInx system

The effect of In impurity on the crystallization kinetics and the changes taking place in the structure of (Se₇Te₃) have been studied by DTA measurements at different heating rates (α=5 deg·min^?1, 10 deg·min^?1, 15 deg·min^?1 and 20 deg·min^?1). From the heating rate dependence of the values ofT _g,T _c andT _p, the glass transition activation energy (E _t) and the crystallization activation energy (E _c) have been obtained for different compositions of (Se₇Te₃)_100?xIn_x (0≤×≤20). The variation of viscosity as a function of temperature has been evaluated using Vogel-Tamman-Fulcher equation. The crystallization data are analysed using Kissinger's and Matusita's approach for nonisothermic crystallization. It has been found that for samples containing In=0, 10, 15, 20 at%, three dimensional nucleation is predominant whereas for samples containing In=5 at%, two dimensional nucleation is the dominant mechanism. The compositional dependence ofT _g and crystallization kinetics are discussed in terms of the modification of the structure of the Se?Te system.     

Thermochemical study of [Sm(C7H5O3)2·(C4H6NO2S)]·2H2O

The product from reaction of samarium chloride hexahydrate with salicylic acid and Thioproline, [Sm(C₇H₅O₃)₂·(C₄H₆NO₂S)]·2H₂O, was synthesized and characterized by IR, elemental analysis, molar conductance, and thermogravimetric analysis. The standard molar enthalpies of solution of [SmCl₃·6H₂O(s)], [2C₇H₆O₃(s)], [C₄H₇NO₂S(s)] and [Sm(C₇H₅O₃)₂·(C₄H₇NO₂S)·H₂O(s)] in a mixed solvent of absolute ethyl alcohol, dimethyl sulfoxide(DMSO) and 3 mol L^?1 HCl were determined by calorimetry to be Δ_s H _m ^Φ [SmCl₃ δ6H₂O (s), 298.15 K]= ?46.68±0.15 kJ mol^?1 Δ_s H _m ^Φ [2C₇H₆O₃ (s), 298.15 K]= 25.19±0.02 kJ mol^?1, Δ_s H _m ^Φ [C₄H₇NO₂S (s), 298.15 K]=16.20±0.17 kJ mol^?1 and Δ_s H _m ^Φ [Sm(C₇H₅O₃)₂·(C₄H₆NO₂S)]·2H₂O (s), 298.15 K]= ?81.24±0.67 kJ mol^?1. The enthalpy change of the reaction (1) $$ SmCl_3 \cdot 6H_2 O(s) + 2C_7 H_6 O_3 (s) + C_4 H_7 NO_2 S(s) = Sm(C_7 H_5 O_3 )_2 \cdot (C_4 H_6 NO_2 S) \cdot 2H_2 O(s) + 3HCl(g) + 4H_2 O(1) $$ was determined to be Δ_s H _m ^Φ =123.45±0.71 kJ mol^?1. From date in the literature, through Hess’ law, the standard molar enthalpy of formation of Sm(C₇H₅O₃)₂(C₄H₆NO₂S)δ2H₂O(s) was estimated to be Δ_s H _m ^Φ [Sm(C₇H₅O₃)₂·(C₄H₆NO₂S)]·2H₂O(s), 298.15 K]= ?2912.03±3.10 kJ mol^?1.     

Molecular structure and conformation of 2,3-dichloro-1-propene as determined by gas-phase electron diffraction

The molecular structure and conformation of 2,3-dichloro-1-propene have been determined by gas-phase electron diffraction at nozzle temperatures of 24, 90 and 273°C. The molecules exist as a mixture of two conformers with the chlorine atoms anti (torsion angle ∠φ = 0°) or gauche (∠φ = 109°) to each other and with the anti form the more stable. The composition (mole fraction) of the vapor with uncertainties estimated at 2σ was found to be 0.55 (0.08), 0.49 (0.08) and 0.41 (0.10) at 24, 90 and 273°, respectively. These values correspond to an energy difference with estimated standard deviation ΔE° = E°_g-E°_a = 0.7 ± 0.3 kcal mol^?1 and an entropy difference ΔS° = S°_g-S°_a = 0.6 ± 0.9 cal mol^?1 K^?1. Some of the diffraction results, together with spectroscopic observations, permit the evaluation of an approximate torsional potential function of the form 2V = V₁ (1 - cos φ) + V₂ (1 - cos 2φ) + V₃ (1 - cos 3φ); the results are V₁ = 4.4 ± 0.5, V₂ = ?2.9 ± 0.5 and V₃ = 4.8 ± 0.2, all in kcal mol^?1. The results at 24°C for the distance (r_a) and angle (∠_α) parameters, with estimated uncertainties of 2σ, are: r(C_sp²-H) = 1.098(0.020)Å, r(C_sp³-H) = 1.103(0.020)Å, r(CC) = 1.334(0.009)Å, r(C-C) = 1.504(0.013)Å, r(C_sp²-Cl) = 1.752(0.021)Å, r(C_sp³-Cl) = 1.776(0.020)Å, ∠C-CC = 127.6(1.1)°, ∠C_sp³-C_sp²-Cl = 110.2(1.0), ∠C_sp²-C_sp³-Cl = 113.1(1.2)°, ∠H-C_sp³-H = 109.5° (assumed), ∠CC-H = 120.0° (assumed) and ∠φ = 108.9(3.4)°.     

Thermal [1,5] sigmatropic rearrangements in (σ-7-cycloheptatrienyl)triphenyltin and (σ-5-cyclohepta-1,3-dienyl)triphenyltin: A 1H and 13C NMR reinvestigation

It has been confirmed by ¹H and ¹³C NMR spectroscopies that Sn(σ-C₇H₇)Ph₃ undergoes either 1,4- or 1,5-shifts of the SnPh₃ moiety around the cycloheptatrienyl ring with ΔH³ = 13.8 ± 0.4 kcal mol^?1, ΔS3 = ?5.6 ± 1.2 cal mol^?1 deg^?1, and ΔG³₃₀₀ = 15.44 ± 0.14 kcal mol^?1. Similarly, (σ-5-cyclohepta-1,3-dienyl)triphenyltin undergoes 1,5-shifts with ΔH³ = 12.4 ± 0.6 kcal mol^?1, ΔS³ = ?11.2 ± 1.8 cal mol^?1 deg^?1, and ΔG³₃₀₀ = 15.76 ± 0.13 kcal mol^?1. It is therefore probable that Sn(σ-5-C₅H₅)R₃ and Sn(σ-3-indenyl)R₃ do not undergo 1,2-shifts as previously suggested but really undergo 1,5-shifts.     

Spectrophotometric study of complexes of mercury(II) with mono- and dithiosemicarbazones

The formation of complexes at pH 4.7 of the Hg(II) with five monothiosemicarbazone and two dithiosemicarbazone has been studied. The mercury(II) reacts with monothiosemicarbazones of salicylaldehyde (λ_max = 363 nm, E = 1.69 × 10⁴liters · mol^?1cm^?1), pi-colinadehyde (λ_max = 363 nm, E = 2.38 × 10⁴liters · mol^?1cm^?1), 6-methyl-picolinaldehyde (λ_max = 363 nm, E = 2.28 × 10⁴liters · mol^?1cm^?1), di-2-pyridylketone (λ_max = 380 nm, E = 2.08 × 10⁴liters · mol^?1cm^?1), and o-naphthoquinone (λ_max = 540 nm, E = 1.03 × 10⁴liters · mol^?1cm^?1) and with dithiosemicarbazones of 1,4-dihydroxyphthalimide (λ_max = 430 nm, E = 2.56 × 10⁴liters · mol^?1cm^?1) and dipyridylglyoxal (λ_max = 363 nm, E = 2.37 × 10⁴liters · mol^?1cm^?1). A critical comparison of the stoichiometry and apparent stability constant of complexes with mono- and dithiosemicarbazones is given.     

The low-temperature (5 to 310 K) heat capacity and thermodynamic functions of cesium fluoroxysulfate (CsSO4F) and the standard potential at 298.15 K for the half-reaction: SO4F−(aq) + 2H+(aq) + 2e− = HSO4−(aq) + HF(aq)

The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO₄F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity C_p^o(T) and standard entropy S^o(T) are (163.46±0.82) and (201.89±1.01) J · K^?1 · mol^?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔH_f^o the Gibbs energy of formation ΔG_f^o(CsSO₄F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol^?1. For the half-reaction: SO₄F^?(aq)+2H⁺(aq)+2e^? = HSO₄^?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V.     

The tris(picolinate)vanadate(II) ion: Redox properties and electron transfer kinetics with cobalt(III) amines

Vanadium(II) ions form with the pyridine-2-carboxylate ligand a deep blue, tris-substituted complex absorbing at 660 nm (ε = 7.2 × 10³ M^?1) cm^?1) with a shoulder at 450 nm. Reversible spectroelectrochemistry and cyclic voltammetry were observed for this complex, with E_{$\text{1}\text{2}$} = ?0.448 V vs NHE, and ΔS_rc^θ = ?6 cal · mol^?1 · deg^?1. Electron transfer kinetics with [CO(en)₃]³⁺ led to k₁₂ = 3100 M^?1 s^?, ΔH^≠ = 12.4 kcal · mol^?1 and ΔS^≠ = ?0.9 cal · mol^?1 · deg^?1 (I = 0.10 M). For the related [Co(NH₃)₆]³⁺ complex, k₁₃ = 1.9 × 10⁴ M^?1 s^?1. The self-exchange rate constant and activation parameters were analysed in terms of relative Marcus theory.     

Thermochemical Study on [La(Hsal)2•(tch)]•2H2O [Hsal＝salicylate ( ), tch＝thioprolinate (C4H6NO2S-)]

The product from reaction of lanthanum chloride heptahydrate with salicylic acid and thioproline, [La(Hsal)2•(tch)]•2H2O, was synthesized and characterized by IR, elemental analysis, molar conductance, thermogravimatric analysis and chemistry analysis. The standard molar enthalpies of solution of LaCl3•7H2O (s), [2C7H6O3 (s)], C4H7NO2S (s) and [La(Hsal)2•(tch)]•2H2O (s) in a mixed solvent of absolute ethyl alcohol, dimethyl sulfoxide (DMSO) and 3 mol•L－1 HCl were determined by calorimetry to be [LaCl3•7H2O (s), 298.15 K]＝(－102.36±0.66) kJ•mol－1, [2C7H6O3 (s), 298.15 K]＝(26.65±0.22) kJ•mol－1, [C4H7NO2S (s), 298.15 K]＝(－21.79±0.35) kJ•mol－1 and {[La(Hsal)2•(tch)]•2H2O (s), 298.15 K}＝(－41.10±0.32) kJ•mol－1. The enthalpy change of the reaction LaCl3•7H2O (s)＋2C7H6O3 (s)＋C4H7NO2S (s)＝[La(Hsal)2•(tch)]•2H2O (s)＋3HCl (g)＋5H2O (l) (Eq. 1) was determined to be ＝(41.02±0.85) kJ•mol－1. From date in the literature, through Hess’ law, the standard molar enthalpy of formation of [La(Hsal)2•(tch)]•2H2O (s) was estimated to be {[La(Hsal)2•(tch)]•2H2O (s), 298.15 K}＝(－3017.0±3.7) kJ•mol－1.     

A photoionization study of the van der Waals molecule C2H4 · HCl

The dissociation energy of the C₂H₄ · HCl van der Waals complex was determined to be 3.18±0.73 kcal mol^?1 by a dissociative photoionization technique. C₂H₄ · HCl was produced by free expansion of a 1:4 mixture of C₂H₄ in HCl and the clusters were ionized with tunable synchrotron radiation. The photoionization efficiency function of (C₂H₄ · HCl)⁺ from C₂H₄ · HCl was determined between 600 and 1,300 Å and the onset for (C₂H₄ · HCl)⁺ was established as 1,163±2 Å = 10.66±0.02 eV; these values give ΔH _f ⁰ (C₂H₄ · HCl) = ?10.7±0.7 kcal mol^?1 and ΔH _f ⁰ (C₂H₄·HCl⁺)=235.1±0.9 kcal mol^?1. A complex ion dissociation energyD ₀(C₂H₄ · HCl⁺) = ?0.3±0.9 kcal mol^?1 was calculated from the results. The major features on the PIE curve for C₂H₄ · HCl⁺ can be analyzed in terms of the known energetic features of C₂H ₄ ⁺ and HCl. An extended energy diagram for the C₂H₄ + HCl system is presented.     

Low-temperature thermodynamic properties of L- and DL-valines

Heat capacities C _p(T) of L-valine and DL-valine were measured in the temperature range 6–300 K with an adiabatic calorimeter; thermodynamic functions were calculated based on these measurements. At 298.15 K, the values of heat capacity, C _p; entropy, S _m ⁰ (T) ? S _m ⁰ (0); enthalpy, H _m ⁰ (T) ? H _m ⁰ (0) of L-valine are equal, respectively, to 167.9 ± 0.3 J K^?1 mol^?1; 178.5 ± 0.4 J K^?1 mol^?1; and 27510 ± 60 J mol^?1. For DL-valine, these values are equal, respectively, to 167.3 ± 0.3 J K^?1 mol^?1, 174.4 ± 0.3 J K^?1 mol^?1, and 27000 ± 50 J mol^?1. The difference between the heat capacities of enantiomer and racemate has been calculated and compared with the similar data for serines, cysteines, and phenylglycines.     

Zur Thermochemie der Zinnhalogenide

The enthalpy change of the reaction at 298 K between Br₂ (l) and Sn(c) in CS₂ as solvent giving SnBr₄ (s) has been determined by calorimetry to be (?374, 2±1.4) kJ·mol^?1, [(?89.45±0.33) kcal·mol^?1]. By the same method the heat of solution of SnBr₄ (c) in CS₂ has been found to be (11.9±0.3) kJ·mol^?1, [(2.84±0.08) kcal·mol^?1]. Combining these results, a value of (?386.1±1.5) kJ·mol^?1, [(?92.3±0.4) kcal·mol^?1] is derived for the standard heat of formation of SnBr₄ (c). Substituting this figure in the thermochemical cycle hitherto used for calculating the heat of formation of SnBr₄ (c) gives ?124.3 kcal·mol^?1 for the standard heat of formation of SnCl₄ (l), which is in reasonable agreement with a recent determination of this quantity⁸.     

Values of p(Vm, T) for n-decane up to 300 MPa and 673 K

For n-decane (p, V_m, T) has been determined from 298 to 673 K and from atmospheric pressure to 300 MPa by measuring p(T) at constant molar volumes V_m from 190 to 1050 cm³·mol^?1. The experimental results are tabulated and represented by equations. Thermal pressure coefficients have been calculated.     

Transition-metal mediated heteroatom removal by reactions of FeL+ [L=O,C4H6, c-C5H6, c-C5H5, C6H6, C5H4(=CH2)] with furan,thiophene, and pyrrole in the gas phase

Reactions of Fe⁺ and FeL⁺ [L=O, C₄H₆, c-C₅H₆, C₅H₅, C₆H₆, C₅H₄(=CH₂)] with thiophene, furan, and pyrrole in the gas phase by using Fourier transform mass spectrometry are described. Fe⁺, Fe(C₅H₅)⁺, and FeC₆H ₆ ⁺ yield exclusive rapid adduct formation with thiophene, furan, and pyrrole. In addition, the iron-diene complexes [FeC₄H ₆ ⁺ and Fe(c-C₅H₆)⁺], as well as FeC₅H₄(=CH₂)⁺ and FeO⁺, are quite reactive. The most intriguing reaction is the predominant direct extrusion of CO from furan by FeC₄H₆ ⁺, Fe(c-C₅H₆)⁺, and FeC₅H₄(=CH₂)⁺. In addition, FeC₄H ₆ ⁺ and Fe(c-C₅H₆)⁺ cause minor amounts of HCN extrusion from pyrrole. Mechanisms are presented for these CO and HCN extrusion reactions. The absence of CS elimination from thiophene may be due to the higher energy requirements than those for CO extrusion from furan or HCN extrusion from pyrrole. The dominant reaction channel for reaction of Fe(c-C₅H₆)⁺ with pyrrole and thiophene is hydrogen-atom displacement, which implies D^O(Fa(N₅H₅)⁺-C₄H₄X)>D^O(Fe(C₅H₅)⁺-H)=46±5 kcal mol^?1. D^O(Fe⁺-C₄H₄S) and D^O(Fe⁺-C₄H₅N)=D^O(Fe⁺-C₄H₆)=48±5 kcal mol^?1. Finally, 55±5 kcal mol^?1=D^O(Fe⁺-C₆H₆)>D^O(Fe⁺-C₄H₄O)>D^O(Fe⁺-C₂H₄)=39.9±1.4 kcal mol^?1. FeO⁺ reacts rapidly with thiophene, furan, and pyrrole to yield initial loss of CO followed by additional neutral losses. D^O(Fe⁺-CS)>D^O(Fe⁺-C₄H₄S)≈48±5 kcal mol^?1 and D^O(Fe⁺-C₄H₅N)≈48±5 kcal mol^?1>D^O(Fe⁺-HCN)>D^O(Fe⁺-C₂H₄)=39.9±1.4 kcal mil^?1.     

ortho-, meta- and para-nitrophenylgold(I) complexes

Treatment of [BzPh₃P][AuCl₂] with [Hg(x-C₆H₄NO₂)₂] (x = o, m, or p) gives anionic gold(I) complexes of the type [BzPh₃P][Au(R)Cl](R = o-, m- or p-C₆H₄NO₂, Bz = C₆H₅CH₂). The chloro ligand in [Au(o-C₆H₄NO₂)Cl]^? can be replaced by bromo or iodo ligands by use of NaBr or NaI. The anions [Au(R)Cl]^? react with neutral monodentate ligands, L, to give neutral mononuclear complexes [Au(R)L] (R = o-C₆H₄NO₂, L = PPh₃, AsPh₃; R = m-C₆H₄NO₂, L = PPh₃) and with 1,2-bis(diphenylphosphino)ethane (dpe) to give [Au₂(R)₂(dpe)] (R = o-C₆H₄NO₂). The corresponding [Au(p-C₆H₄NO₂)Cl]^? reacts with PPh₃ or AsPh₃ to give mixtures containing [AuClL]. The anionic ortho-nitrophenylgold(I) complex is much more stable than its meta- or para-nitrophenyl isomers. These are thought to be the first reports of nitrophenylgold(I) complexes.     

Isotope Effects and Final Products in Pyrolysis of Halomethanes and Perfluoroalkyl Iodides

Final products of isothermal pyrolysis of CF₂HBr, CF₂ClBr, CH₃I, CH₂I₂, CHI₃, i-C₃F₇I, and C₄F₉I were determined and mechanisms of their formation were proposed. The enthalpy of formation of the free biradical CFBr^·· (Δ_fH ₀ ⁰ = 80±20, Δ _fH ₀ ²⁹⁸ = 60±20 kJ mol^?1) was estimated. The dissociation energies E_{D, 0}(ID₂C-D), E_D,298(ID₂C-D), and E_D,0(IH₂C-D) equal to 437±6, 444±6, and 435±4 kJ mol^?1, respectively, were determined.     

Mechanism of the reaction of N-p-tosylsulphilimine and related compounds with thiophenolate ion

The reaction of alkyl aryl N-p-tosylsulphilimines with thiophenolate ion was found to afford quantitatively the sulphide that arises by an S_N2 like reaction on the carbon atom adjacent to the tri-valent sulphur atom. This reaction was also found to proceed smoothly with such compounds as sulphoxides and sulphones and sulphoxmanes. The kinetic study on the reaction between aryl methyl N-p-tosylsulphilimine with thiophenolate ion in DMF reveals that the reaction is of second order, namely, first order with respect to each thiophenolate ion and the sulphilimine. The enthalpy and entropy of activation for the reaction are ΔH^≠ = ?17· kcal/mol and ΔS^≠ = ?5·7 eu respectively. The effect of substituents in the reaction, p-XC₆H₄⁺(^?SO₂C₆H₄Y-p)CH₃ + p-ZC₆H₄SK is nicely correl with Hammett σ values giving ?_x = + 2·4, ?_y = + 1·2 and ?_z = ?1·8 respectively. Meanwhile, a marked steric retardation by a bulky alkyl group in alkyl phenyl N-p-tosylsulphilimine is observed. Furthermore, from the stereochemical study of the reaction using an optically active sec-octyl phenyl N-p-tosylsulphilimine with thiophenolate ion it is concluded that the reaction proceeds via a typical S_N2 process on α-carbon atom attached to the tri-valent sulphur atom.