Thermodynamique de substances azotees. IX. Etude thermochimique de la benzamide. Comparaison des grandeurs energetiques liees a la structure de quelques amides et thioamides

The enthalpy of sublimation of benzamide was obtained by calorimetry in the range 323<T (K)<350. From values of ΔH_sub(T)=f(T), it was possible to determine ΔH⁰_sub (298.15 K)=101.7±1.0 kJ mole^?1. Using previous data on ΔH⁰_f (c, 298.15 K) obtained by combustion calorimetry, the value of ΔH⁰_f (g, 298.15 K)=?100.9±1.2 kJ mole^?1 was calculated. With the use of energetical values concerning thioacetamide, thiobenzamide and thiourea, on the one hand, and acetamide, benzamide and urea, on the other, a comparative study was made.     

Thermodynamics of redox reactions involving nicotinamide adenine dinucleotide

Literature data on the thermodynamics of redox nicotinamide adenine dinucleotide (NAD) dependent reactions have been analyzed. It has been established that for the redox reaction of NAD

where all substances except H₂ are in the aqueous buffer with the ionization enthalpy equal to zero, the most reliable thermodynamic parameters should be considered as: ΔH(298.15 K; pH 7)=?27.4±1.7 kJ mole^?1; ΔG (298.15K; pH 7)=±17.8 kJ mole^?1. From the above thermodynamic parameters of the reaction ΔH, ΔG and ΔS for reactions of NAD with natural substrates, synthetic mediators and some inorganic compounds have been calculated.     

Thermal decomposition of zinc and cadmium zirconyl oxalates

The enthalpy of formation at 298.15 K of the polymer Al₁₃O₄(OH)₂₈(H₂O)³⁺₈ and an amorphous aluminium trihydroxide gel was studied using an original differential calorimetric method, already developed for adsorption experiments, and aluminium-27 NMR spectroscopy data. ΔH_f “Al₁₃” (298.15 K) = ? 602 ± 60.2 kJ mole^?1 and ΔH_f Al(OH)₃ (298.15 K) = ? 51 ± 5 kJ mole^?1. Using theoretical values of ΔG_R “Al₁₃” and ΔG_R Al(OH)₃, we calculated ΔG_f “Al₁₃” (298.15 K) = ? 13282 kJ mole^?1; ΔS_f “Al₁₃” (298.15 K) = + 42.2 kJ mole^?1; ΔG_f Al(OH)₃ (298.15 K) = ? 782.5 kJ mole^?1; and ΔS_f Al(OH)₃ (298.15 K) = + 2.4 kJ mole^?1.     

Thermodynamic properties of citric acid and the system citric acid-water

The binary system citric acid-water has been investigated with static vapour pressure measurements, adiabatic calorimetry, solution calorimetry, solubility measurements and powder X-ray measurements. The data are correlated by thermodynamics and a large part of the phase diagram is given. Molar heat capacities of citric acid are given from 90 to 330 K and for citric acid monohydrate from 120 to 300 K. The enthalpy of compound formation Δ_comH (298.15 K)=(?11.8±1) kJ mole^?1.     

Determination calorimetrique de l'enthalpie de formation des alliages (Al,Ba) riches en aluminum

The heats of formation of some aluminium-barium alloys have been determined by drop calorimetry at high temperature. The heats of mixing of pure liquid Al and Ba to give the liquid alloy are Δ_mH(x_Ba=O.056, 1215 K)=?6.6 kJ mole^?1 and Δ_mH(x_Ba=O.333, 1215 K)=?31.0 kJ mole^-1. To measure its heat of formation, the solid compound Al₄Ba was precipitated by addition of pure barium from a liquid (Al, Ba) bath. It was found that Δ_fH(Al_0.8Ba_O.2, solid, 1215 K)=-(37.1 ? 1.5) kJ mole^?1 with reference to the pure metals in the solid state.     

Thermochemistry of hydrogen tungsten bronze phases HxWO3

The enthalpies of formation of two hydrogen tungsten bronze phases H_0.35WO₃ and H_0.18WO₃ have been determined by solution calorimetry. Values obtained for formation from H₂(g) and WO₃(s) at 298.15 K were H_0.35WO₃(s), ?9.6 ± 0.8 kJ mole^?1 and H_0.18WO₃(s), ?4.8 ± 0.6 kJ mole^?1. The stabilities of these phases towards decomposition, disproportionation and oxidation are discussed.     

Equilibrium sublimation and thermodynamic properties of SnS

Knudsen effusion studies of the sublimation of polycrystalline SnS, prepared by annealing and chemical vapor transport, have been performed employing vacuum micro-balance techniques in the temperature range 733–944 K and at pressures ranging from about 6 × 10^?3 to 11 Pa.The third-law heats of sublimation and second-law entropy of reaction SnS(s) = SnS(g) were determined to be ΔH⁰₂₉₈ = 220.4 ± 3.0 kJ mole^? and ΔS⁰₂₉₈ = 162.4 ± 4.5 J K^?1 mole^?1. From these data the standard heat of formation and absolute entropy of SnS(s) were calculated to be ?102.9 ± 4.0 kJ mole^?1 and 79.9 ± 6.0 J K^?1, respectively.     

Integral heat of dissolution of potassium chlorate in water at 298.15 K

The heat of dissolution of potassium chlorate in water at 298.15 K has been measured on an LKB 8700-1 calorimeter in the concentration range 0.063–0.659 m. The concentration dependence of the measured data was fitted by an empirical equation ΔH_m (kJ mole^?1) = 41.353₈ + 1.862₆m^{$\text{1}\text{2}$} ? 6.430₀m which was derived from our and Andauer—Lange data. The heat of crystallization calculated from this dependence was ΔH_cryst. = 34.7 ± 0.5 kJ mole^?1, which agrees with data calculated for potassium chlorate from solubility and activity data.     

Enthalpy of formation of wulfenite (natural lead molybdate)

A thermochemical study of wulfenite, i.e., natural lead molybdate PbMoO₄ (Kyzyl-Espe field deposit, Central Kazakhstan), is performed on a Setaram high-temperature heat-flux Tian-Calvet microcalorimeter (France). Enthalpies of the formation of wulfenite from oxides Δ_f H _ox ^o (298.15 K) = ?88.5 ± 4.3 kJ/mol and simple substances Δ_f H°(298.15 K) = ?1051.2 ± 4.3 kJ/mol were determined by means of melt calorimetry. The Δ_f G°(298.15 K) of wulfenite corresponding to ?949.1 ± 4.3 kJ/mol was calculated using data obtained earlier for S°(298.15 K) = 161.5 ± 0.27 J/(K mol).     

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.     

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.     

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.     

Thermochemical investigation of natural antlerite

Thermal and thermochemical investigations of natural hydroxyl-bearing copper sulfate Cu₃SO₄(OH)₄??antlerite have been carried out. The stages of its thermal decomposition have been studied employing the Fourier-transform IR spectroscopy. The enthalpy of formation of antlerite from the elements ??_f H _m ^o (298.15?K)?=?(?1750?±?10)?kJ?mol^?1 has been determined by the method of oxide melt solution calorimetry. Using value of S _m ^o (298.15?K), equal to (263.46?±?0.47)?J?K^?1?mol^?1, obtained earlier by the method of adiabatic calorimetry, the Gibbs energy value of ??_f G _m ^o (298.15?K)?=?(?1467?±?10)?kJ?mol^?1 has been calculated.     

Die Bildungsenthalpie von Zinndijodid,SnJ2 (c)

The heat of reaction for SnJ₂ (c)+J₂ (c)+4045 CS₂ (l)=[SnJ₄; 4045 CS₂] (sol) has been determined to be (?41.12±0.55) kJ mol^?1, [(?9.83±0.13) kcal mol^?1] by isoperibol solution calorimetry. Combining this result with the heat of formation of SnJ₄ in CS₂ determined in a previous investigation¹¹ the value (?153.9±1.40) kJ mol^?1, [(?36.9±0.33) kcal mol^?1] has been derived for the heat of formation, ΔH _f ^ι (SnJ₂;c; 298.15 K), of tin diiodide.     

Removal of Zn(II) Ions from Aqueous Solution Using BPHA‐Impregnated Polyurethane Foam

Zn(II) ions sorption onto N‐Benzoyl‐N‐Phenylhydroxylamine (BPHA) impregnated polyurethane foam (PUF) has been studied extensively using radiotracer and batch techniques. Maximum sorption (～98%) of Zn(II) ions (8.9 × 10^?6 M) onto sorbent surface is achieved from a buffer of pH 8 solution in 30 minutes using 7.5 mg/mL of BPHA‐impregnated polyurethane foam at 283 K. The sorption data follow Langmuir, Freundlich and Dubinin‐Radushkevich (D‐R) isotherms. The Langmuir constants Q = 18.01 ± 0.38 μ mole g^?1 and b = (5.39 ± 0.98) × 10³ L mole^?1 have been computed. Freundlich constants 1/n = 0.29 ± 0.01 and C_m = 111.22 ± 12.3 μ mole g^?1 have been estimated. Sorption capacity 31.42 ± 1.62 μ mole g^?1, β = ?0.00269 ± 0.00012 kJ² mole^?2 and energy 13.34 ± 0.03 kJ mole^?1 have been evaluated using D‐R isotherm. The variation of sorption with temperature yields ΔH = ?77.7 ± 2.8 k J mole^?1, ΔS = ?237.7 ± 9.3 J mole^?1 K^?1 and ΔG = ?661.8 ± 117.5 k J mol^?1 at 298 K reflecting the exothermic and spontaneous nature of sorption. Cations like Fe(III), Ce(III), Al(III), Pb(II) and Hg(II) and anions, i.e., oxalate, EDTA and tartrate, reduce the sorption significantly, while iodide and thiocyanate enhanced the sorption of Zn(II) ions onto BPHA‐impregnated polyurethane foam.     

Fourier transform-ion cyclotron resonance study of the gas-phase acidities of germane and methylgermane; Bond dissociation energy of germane

An accurate gas-phase acidity for germane (enthalpy scale, equivalent to the proton affinity of GeH₃ ^?), ΔH _acid ^o(GeH₄) = 1502.0 ± 5.1 kJ mol^?1, is obtained by constructing a consistent acidity ladder between GeH₄, and H₂S by using Fourier transform-ion cyclotron resonance spectrometry, and 0 and 298.15 K values for the first bond dissociation energy of GeH₄ are proposed: D₀ ^o(H₃Ge-H) = 352 ± 9 kJ mol^?1; D ^o(H₃Ge-H) = 358 ± 9 kJ mol^?1, respectively. These results are compared with experimental and theoretical data reported in the literature. Methylgermane was found to be a weaker acid than germane by approximately 35 kJ mol^?1: ΔH _acid ^o = 1536.6 kJ mol^?1.     

Enthalpy of the formation of natural hydrous aluminum hydroxosulfate (aluminite)

A thermochemical study of natural aluminum hydroxosulfate Al₂[(OH)₄SO₄] · 7H₂O, aluminite (Nakhodka deposit, West Chukotka, Russia) is performed on a Tian-Calvet “Setaram” high-temperature heat-conducting microcalorimeter (France). The enthalpy of aluminite formation from simple compounds is obtained via the melt calorimetry of dissolution, Δ_f H ^○(298.15 K) = ?4986 ± 21 kJ/mol.     

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.     

Vapour pressures and sublimation enthalpies of thymine and cytosine

The vapour pressures of cytosine and thymine were measured using the torsion-effusion technique. The sublimation processes of cytosine and thymine were investigated over the temperature ranges 480–553 K and 420–503 K, respectively. The following pressure—temperature equations were derived by least-squares treatment of the vapour pressure data

The standard sublimation enthalpies were obtained by second-and third-law treatment of the experimental data and the values ΔH⁰₂₉₈ = 167 ± 10 kJ mole^?1 and ΔH⁰₂₉₈ = 138 ± 10 kJ mole^?1 were derived for cytosine and thymine, respectively. IR and Raman spectra were recorded in the gas phase in order to evaluate the thermodynamic functions of gaseous cytosine and thymine.     

Vaporization chemistry and thermodynamics in the CdGa2S4-Ga2S3 system

The chemistry and thermodynamics of vaporization of CdGa₂S₄(s), CdGa₈S₁₃(s), and Ga₂S₃(s) were studied by computer-automated, simultaneous Knudsen-effusion and torsion-effusion, vapor pressure measurements in the temperature range 967–1280 K. The vaporization was incongruent with loss of Cd(g) + 1/2 S₂(g) and production of CdGa₈S₁₃(s), a previously unknown compound, in equilibrium with CdGa₂S₄(s), until the solid became CdGa₈S₁₃ only. Then, incongruent vaporization continued with production of Ga₂S₃(s) until the solid was Ga₂S₃ only. The latter vaporized congruently. The ΔH°(298 K) of combination of one mole of CdS(s) with one mole of Ga₂S₃(s) to give CdGa₂S₄(s) was ?22.6 ± 0.9 kJ mole^?1. The 2H2(298 K) of combination of one mole of CdS(s) with four moles of Ga₂S₃(s) to give CdGa₈S₁₃(s) was ?25.5 ± 1.1 kJ mole^?1. The 2H2(298K) of CdGa₈S₁₃(s) with respect to disproportionation into CdGa₂S₄(s) and 3 Ga₂S₃(s) was ?2.8 ± 0.6 kJ mole^?1. CdGa₈S₁₃(s) was not observed at room temperature. The 2H2(298 K) of vaporization of the residual Ga₂S₃(s) was 663.4 ± 0.8 kJ mole^?1, which compared well with a value of 661.4 ± 0.3 kJ mole^?1 already available from the literature. Implications of small variations in stoichiometry of compounds in this study were observed and are discussed.