Thermodynamics of vaporization of some cyclic perfluorocarbons

The temperature dependence of the saturation vapor pressure of perfluoro-meta-dimethylcyclohexane, (CF₃)₂C₆F₁₀, has been determined by the ebulliometric method in the moderate pressure range from 8.4 to 101.6 kPa. Enthalpies of vaporization have been obtained calorimetrically for perfluorobicyclo(4,4,0)dec(1,6)ene, C₁₀F₁₆, and (CF₃)₂C₆F₁₀ at T = 298.15 K. Densities of C₁₀F₁₆ have been measured in the small temperature range from 293 to 338 K. Critical parameters have been estimated from vapor pressure data and densities for the substances under study and for some mono- and bicyclo-perfluorocarbons investigated earlier. A second-order group additivity method has been applied to predict the vaporization enthalpies of some cyclic perfluorocarbons.     

Thermodynamics of vaporization of gallium trichloride

The unsaturated and saturated pressures of gallium trichloride vapor were measured by the static method with membrane-gauge manometers in wide pressure (0.2–760 Torr) and temperature (313–1071 K) intervals. Scanning calorimetry was used to determine the thermodynamic characteristics of GaCl₃ fusion. The thermodynamic characteristics were obtained for sublimation, fusion, vaporization, and association in the vapor of GaCl₃ molecules. The enthalpies of formation and the absolute entropies of GaCl₃ in the liquid and gaseous phases and Ga₂Cl₆ in the gaseous phase were calculated using literature data. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1266–1269, July, 2007.     

Thermodynamics of some perfluorocarbon gases in water

The solubilities of CF₄ and C₂F₆ gases in H₂O and D₂O in the temperature range of 5 to 30°C at 5° intervals and C₃F₈ and c-C₄F₈ gases in H₂O over the temperature ranges of 5 to 15°C and 5 to 30°C, respectively, have been determined. From the solubility data various thermodynamic quantities for the process of dissolution have been derived. These data were compared with our results of applying the scaled-particle theory to gain an insight into the various thermodynamic processes accompanying the gas dissolution. One of our conclusions is that the hydrophobicity of the perfluorocarbons is greater than that of the corresponding alkanes.     

The enthalpies of vaporization of some hydrocarbons with three-membered rings

The enthalpies of vaporization of four compounds with three-membered rings (bicyclopropyl, 1,2-bicyclopropylacetylene, 1-cyclopropylpentadiine-1,3, and 1,2,2-trimethylcyclopropene) were determined calorimetrically. The temperature dependence of saturated vapor pressure of 1,2,2-trimethylcyclopropene was studied by ebulliometry, and the results were approximated by the equation lnp = A + B/T. The enthalpy of vaporization, normal boiling temperature, critical parameter, and similarity criterion according to the law of corresponding states in the variant suggested by Filippov were calculated. The calculated corrections to the enthalpy of vaporization (kJ/mol) for the cyclopropene ring containing methyl substituents are discussed in comparison with the data on related compounds.     

Thermodynamics and molecular dynamics of some ferrocene derivatives

The heat capacities of acetylferrocene, 1,1′-diacetylferrocene, and 1,1′-diethylferrocene were investigated by low-temperature adiabatic calorimetry in the temperature range from 5 to 300 K and their thermodynamic functions were calculated. The enthalpies of combustion of the substances were determined by calorimetry of combustion, and the thermodynamic functions of their formation were calculated by quantum chemistry methods. Inter- and intramolecular interactions of the ferrocene derivatives were also studied by the methods of molecular mechanics and molecular dynamics. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1668–1676, September, 1999.     

Thermodynamics of some long-chain biradicals studied by EPR spectroscopy

Four biradicals of differing chain lengths have been prepared by spin-labelling the sulphhydryl groups of dithiothreitol. Temperature-dependent EPR spectra of these biradicals indicate that the dynamics of biradicals is associated with both fast and slow exchanges of conformations. The three-conformational model incorporating cage configuration is found to be more appropriate. Certain thermodynamic parameters of conformationalchanges have been calculated from the experimental EPR parameters, obtained by the use of simulation procedures developed recently.     

Thermal analysis study on vaporization of some analgesics. Acetanilide and derivatives

The thermal behaviour of acetanilide (Ac) and two of its analogues, namely the para-ethoxyacetanilide (p-Eto Ac) and the para-bromoacetanilide (p-Br Ac), which are used as analgesics in the pharmaceutical industry was studied with a simultaneous TG/DSC unit. The examined analgesics showed two endothermic DSC peaks due to melting and vaporization. By combining the experimental TG data with the corresponding reference vapour pressure data obtained with the Antoine equation the plot of P versus v was derived. From the slope of this equation the constant k-value was determined for Ac. Then, using the same k-value the vapour pressures of p-Eto Ac and p-Br Ac were determined in the same temperature range. The vaporization enthalpies for all the studied compounds were obtained from different methods and a very good agreement was found. Vaporization follows a zero-order kinetics. The activation energy of vaporization (E_vap) was calculated from the dynamic TG experiments, using the Arrhenius equation.     

Determination of some refractory elements and Pb by fluorination assisted electrothermal vaporization inductively coupled plasma mass spectrometry with platform and wall vaporization

Platform and wall vaporization for electrothermal vaporization (ETV)-inductively coupled plasma mass spectrometry (ICP-MS) determination of some refractory elements (Ti, V, Cr, Mo, La and Zr) and Pb were comparatively studied with the use of poly (tetrafluoroethylene) (PTFE) as fluorinating reagent. The factors affecting the vaporization behaviors of the target analytes in the platform and tube wall vaporization including vaporization temperature and time, pyrolytic temperature and time were studied in detail, and the flow rates of carrier gas/auxiliary carrier gas, were carefully optimized. Under the optimal conditions, the signal profiles, signal intensity, interferences of coexisting ions and analytical reproducibility for wall and platform vaporization ETV-ICP-MS were compared. It was found that both wall and platform vaporization could give very similar detection limits, but the platform vaporization provided higher signal intensity and better precision for some refractory elements and Pb than the wall vaporization. Especially for La, the signal intensity obtained by platform vaporization was 3 times higher than that obtained by wall vaporization. For platform vaporization ETV-ICP-MS, the limits of detection (LODs) of 0.001 μg L⁻¹ (La) ~ 0.09 μg L^− 1 (Ti) with the relative standard deviations (RSDs) of 1.5% (Pb) ~ 15.5% (Zr) were obtained. While for wall vaporization ETV-ICP-MS, LODs of 0.005 μg L^− 1 (La) ~ 0.4 μg L^− 1 (Pb) with RSDs of 3.2% (Mo) ~ 12.8% (Zr) were obtained. Both platform and tube wall vaporization techniques have been used for slurry sampling fluorination assisted ETV-ICP-MS direct determination of Ti, V, Cr, Mo, La, Zr and Pb in certified reference materials of NIES No. 8 vehicle exhaust particulates and GBW07401 soil, and the analytical results obtained are in good agreement with the certified values.     

Thermodynamics of the vaporization of alkyl compounds of zinc,selenium, cadmium,tellurium, and their equimolecular solutions

Enthalpies of vaporization for diethylzinc, diethylselenium, dimethylcadmium, and dimethyltellurium, and their equimolecular solutions are determined via calorimetry and tensiometry. It is found that in the liquid phase and the temperature range of 273-368 K, equimolecular solutions of ZnEt₂ · SeEt₂ behave as single-component systems that dissociate into constituting substances upon vaporization. At the same time, equimolecular solutions of ZnEt₂ · SeMe₂, CdMe₂ · SeMe₂, and CdMe₂ · TeMe₂ consist of two components whether in a liquid or vapor phase.     

Thermodynamics of weak interactions: Excess enthalpies of some binary bromoform mixtures

Excess enthalpies of bromoform + toluene, +o-xylene +m-xylene and +p-xylene have been determined at 308.15 K. These compounds have been examined for Barker's theory in order to understand the magnitude and nature of various interactions between the components of these mixtures. It has been concluded that the H-atom and one bromine atom of bromoform interact with the π cloud of the aromatic ring. These conclusions have been supplemented by n.m.r. studies. An approximate distance of the bromoform proton from the plane of the aromatic ring has also been calculated and examined in the light of the proposed geometry of the molecular complexes. Equilibrium constants for the complexations reaction have also been determined.     

Thermodynamics of vinyl ethers—XXI: Evaluation of some cis interaction energies

Thermodynamics of isomerization reactions on some substituted vinyl methyl ethers have been studied for evaluating the magnitudes of the interaction energies S[R¹... R²] between the substituents R¹ and R², juxtaposed in a cis position across the CC bond of vinyl ethers. The results obtained are (values given in kJ mol^-1): S[Me... t-Bu]=18.2±1.0, S[Ph...i-Pr]=11±2, S[i-Pr...Et] =6.1±0.6, S[i-Pr... i-Pr] = 6.0 ± 0.6, S[0...t-Bu]=2.9±0.5, S[O...i-Pr]= -0.7±0.5, S[O...Et] = ?1.5±0.5, S[O...Ph]= ?2.1+-0.6, and S[O... Me] =?2.9 ±0.2 (the symbol O stands for the ethereal oxygen atom of vinyl ethers). The negative interaction energy values reveal that the cis interaction between the ethereal oxygen and the alkyl (aryl) group concerned is stabilizing.     

Thermochemistry of fenamates vaporization

Enthalpies of melting, sublimation and vaporization were determined for diclofenac, flufenamic, and niflumic acids. The validity of thermogravimetric procedure for measuring enthalpy of vaporization of the compounds under investigation was demonstrated.     

Thermodynamics of metal-ligand bond formation: XVI. Base adducts of some organotin compounds

Thermodynamic data have been obtained by calorimetric titration in benzene solution at 30° for reaction of organotin compounds with Lewis bases; data are reported for forty acid/base systems.Ph₃SnCl forms $\text{1}\text{1}$ adducts of low stability with pyridine (py) or 4-methyl-pyridine (4-mepy). Ph₂SnCl₂, Me₂SnCl₂, Bu₂SnCl₂ and Bu₂Sn(NCS)₂ form simultaneously $\text{1}\text{1}$ and $\text{1}\text{2}$ adducts with py or 4-mepy and $\text{1}\text{1}$ adducts with 2,2′-bipyridine or 1,10-phenanthroline (phen); the enthalpies of formation of the phen adducts are similar to those of $\text{1}\text{2}$ adducts with 4-mepy. With BuSnCl₃ and PhSnCl₃ it was not possible to obtain data for each step in addition of pyridine or 4-mepy. Adduct stabilities increase with increasing chloride substitution and in the order Bu < Me < Ph; adducts of Bu₂Sn(NCS)₂ are more stable than those of Bu₂SnCl₂.Tributylphosphine does not react with Ph₃SnCl but gives $\text{1}\text{1}$ adducts with the other tin compounds; only PhSnCl₃ adds a second molecule of this base. The $\text{1}\text{1}$ adducts are more stable than those with heterocyclic bases. Tributylamine brings about disproportionation of the compounds R₂SnX₂ to R₄Sn and SnX₄NBu₃.