Temperature Dependence Of Vapor Pressure Research Articles

Thermochemical study of new volatile palladium(II) and copper(II) β-ketohydrazonates for CVD application

The volatile palladium(II) and copper(II) {O,N}-coordinated bis-chelate complexes of a new type, Pd(dmht)2 and Cu(dmht)2, where dmht = 1,1,1-trifluoro-2-(2,2-dimethylhydrazone)pentan-4-onato, were synthesized, purified and identified by elemental analysis, IR and NMR spectroscopy and mass spectrometry. The thermal behavior of the complexes in the condensed phase was studied by TG-DTA and DSC methods. The temperature dependences of saturated vapor pressure were measured for Pd(dmht)2 and Cu(dmht)2 in the temperature ranges ΔT = (343–388) K (flow method) and ΔT = (321–390) K (flow and Knudsen effusion method), respectively. The ketohydrazonate complexes characterized by close enthalpy and entropy of melting and sublimation processes and the highest volatility among the related compounds. The new complexes were successfully used as precursors for metal-organic chemical vapor deposition of mono- and bimetallic thin films onto Si (100) substrates at the reducing atmosphere.

Modeling Iron Pentacarbonyl Vaporization Accompanied by Vapor Condensation on a Flowing Down Liquid Film

Using iron pentacarbonyl distillation as an example, we analyze the vaporization process in a closed vaporization–condensation system where vapor condenses on a flowing down liquid film. We jointly analyze the mechanisms behind vaporization, vapor transport, condensation, and flowing of the condensate on the inner surface of a vertical tube. We calculate the thickness of the flowing down liquid film, determine the vaporization coefficient for a closed system using experimentally determined temperature dependences of the vaporization rate and saturated vapor pressure, and present the vaporization rate as a function of the vaporization and condensation temperatures, the radius and height of the condensation tube, and the vaporization area of the still residue.

How much different are thermochemical properties of enantiomers and their racemates? Thermochemical properties of enantiopure and racemate of methyl- and butyl lactates.

This work is a contribution to the molecular understanding of the thermodynamic properties of the chiral compounds. A comprehensive thermochemical study of the liquid enantiopure and racemate pairs of optically active alkyl lactates has been performed. Vapor pressures of DL-(±)-, L-(-)-methyl-, and DL-(±)-, L-(-)-n-butyl esters of lactic acid were measured by the transpiration method. The liquid phase standard molar enthalpies of formation of these esters were measured by using the high-precision combustion calorimetry. The standard molar enthalpies of vaporization of alkyl lactates at 298.15 K were derived from vapor pressure temperature dependencies. Thermochemical data of these compounds were collected, evaluated, and tested for internal and external consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas phase enthalpies of formation of alkyl lactates. A critical review of the available thermochemical data for the liquid and crystalline enantiopure and racemate pairs of optically active compounds has been performed. Useful general trends in energetics of sublimation, vaporization, and formation of optically active compounds have been revealed. This knowledge is required for evaluation of new and already available experimental data for the chiral compounds, and it can be helpful to assess volatility or feasibility of processes to separate enantiomers.

Volatile Heteroligand Complexes of Copper(II): New Precursors for Chemical Vapor Deposition of Copper Films

Two heteroligand ketoiminate–diketonate complexes of copper(II), CuL(hfa) (1), L = pentane-2-imino-4-onato, CH3COCHCNHCH 3 – , and CuL′(hfa) (2), L′ = 2,2,6,6-tetramethyl-3-iminoheptane-5-onato, C(CH3)3COCHCNHC(CH)–, were studied as precursors for chemical vapor deposition of copper films. The flow method was employed to measure the temperature dependences of a saturated vapor pressure of these compounds, the thermodynamic parameters of evaporation–sublimation were calculated, and the volatilities of these compounds and thermal behaviors in the condensed and gaseous phases were compared. The copper films were compared, and it was shown that comparatively high growth rates are reached when (2) is used to obtain copper films in hydrogen.

Vapor Cartesian diver

The article proposes a new research object for a general physics course—the vapour Cartesian diver, designed to study the properties of saturated water vapour. Physics education puts great importance on the study of the saturated vapour state, as it is related to many fundamental laws and theories. For example, the temperature dependence of the saturated water vapour pressure allows the teacher to demonstrate the Le Chatelier’s principle: increasing the temperature of a system in a dynamic equilibrium favours the endothermic change. That means that increasing the temperature increases the amount of vapour present, and so increases the saturated vapour pressure. The experimental setup proposed in this paper can be used as an example of an auto-oscillatory system, based on the properties of saturated vapour. The article describes a mathematical model of physical processes that occur in the experiment, and proposes a numerical solution method for the acquired system of equations. It shows that the results of numerical simulation coincide with the self-oscillation parameters from the real experiment. The proposed installation can also be considered as a model of a thermal engine.

Experimental and theoretical thermodynamic properties of RS-(±)- and S-(+)-mandelic acids

The enthalpies of formation of RS-(±)- and S-(+)-mandelic acids were measured using high-precision combustion calorimetry. Vapor pressures of the acids were measured using the transpiration method. The enthalpies of sublimation of these compounds at 298.15 K were derived from vapor pressure temperature dependencies. Molar enthalpies of the solid state phase transitions were measured by the DSC. Thermodynamic data on mandelic acids available from the published sources were collected and combined with our experimental results. Thermochemical properties of studied compounds were evaluated and tested for internal and external consistency with different approaches. The methods of quantum chemistry and statistical physics were used to calculate thermodynamic functions of compounds in the ideal gas state in temperature range 298.15 K–1500 K.

Thermal behavior of volatile palladium(II) complexes with tetradentate Schiff bases containing propylene-diimine bridge

Palladium(II) complexes with tetradentate Schiff bases, Pd(acacpda)(I) and Pd(acacdmpda)(II) (acacpda2−—N,N′-(propylene)-bis(acetylacetoneiminato-), acacdmpda2−—N,N′-(2,2-dimethylpropylene)-bis(acetylacetoneiminato-)), have been synthesized, purified and characterized by elemental analysis, IR and NMR spectroscopy. Complex I was obtained for the first time, and its solid-state structure was investigated by single-crystal X-ray diffraction. It has a discrete molecular structure with the Pd2+ ion being in a distorted square-planar coordination environment formed by N and O atoms of the acacpda2− ligand. The thermal properties of complexes I and II in condensed phase were investigated by thermogravimetry. Compound II transfers into the gas phase almost completely, while compound I evaporates with a partial decomposition. The temperature dependences of saturated vapor pressure were measured by the flow method in the temperature intervals (423–457) and (422–478) K for I and II, respectively. Both complexes were shown to exhibit an excellent stability upon sublimation. The thermodynamic parameters of sublimation processes were calculated to be: ΔsubH440 = (133 ± 4) kJ mol−1, ΔsubS 440 0 = (210 ± 9) J (mol K)−1 for I, ΔsubH450 = (135 ± 1) kJ mol−1, ΔsubS 450 0 = (218 ± 3) J (mol K)−1 for II. It has been found that the complex II with a more bulky Schiff base ligand possesses slightly higher vapor pressure values as compared to I, which is probably due to the lower contribution of weak intermolecular interactions occurring in the crystal structure of II.

Li vaporization property of Li8ZrO6 and Li5AlO4 as tritium breeders

New tritium breeding materials that maintain large tritium breeding ratio for thermonuclear fusion reactors should be developed. In this study, we investigate the lithium-vaporization behavior from the sintered bodies of Li8ZrO6 and Li5AlO4 having high lithium atom densities. From the viewpoint of lithium density, we investigate the possibility of using the sintered compacts of Li8ZrO6 and Li5AlO4 as a tritium breeder. Lithium vaporization rates from the sintered bodies of Li8ZrO6 and Li5AlO4 are high. However, for both materials, the lithium vaporization rate gradually decreases with the annealing time by “self-stabilization” in which the surfaces of each sintered body are covered by the stable layer of the second phase. Considering the temperature dependency of equivalent vapor pressure and the volume fraction of tritium breeding material loaded at high-temperature region, it is suggested that the sintered compacts of Li8ZrO6 and Li5AlO4 have high potentials for the tritium breeder.

Prediction of the temperature dependence of densities and vapor pressures of nonpolar hydrocarbons based on their molecular structure and refractive index data at 20 °C

In a previous publication, a one-parameter equation based on the perturbed chain version of the statistical associating fluid theory, assisted by a group contribution method (1P-PC-SAFT) was proposed for cases where limited experimental data are available (Evangelista and Vargas, Ind. Eng. Chem. Res., 2017). The method was proven to be robust when a single vapor pressure data point was used for the PC-SAFT parameter tuning. Motivated by this fact, a methodology for estimating a saturation data point from refractive index and molecular weight was developed in this work. The proposed correlations also represent an alternative method for calculating critical properties and acentric factor for non-polar hydrocarbons as a function of their molecular weight and refractive index. These alternative correlations to find critical properties can be readily applied to cubic equations of state or methods based on the principle of the corresponding states. The predictive capability of the proposed methodology was assessed over a wide range of temperatures and pressures. Average absolute deviations of 8.24% in vapor pressure and 2.04% in saturated liquid density were obtained for ten representative compounds consisted of aliphatic, aromatics, and cyclic nonpolar hydrocarbons. The results obtained in this work confirm that with the proposed methodology it is possible to relate molecular structure and refractive index of liquid nonpolar hydrocarbons at 20 °C to their density and vapor pressure at high temperatures.

How cores grow by pebble accretion

Context. Planet formation by pebble accretion is an alternative to planetesimal-driven core accretion. In this scenario, planets grow by the accretion of cm- to m-sized pebbles instead of km-sized planetesimals. One of the main differences with planetesimal-driven core accretion is the increased thermal ablation experienced by pebbles. This can provide early enrichment to the planet’s envelope, which influences its subsequent evolution and changes the process of core growth. Aims. We aim to predict core masses and envelope compositions of planets that form by pebble accretion and compare mass deposition of pebbles to planetesimals. Specifically, we calculate the core mass where pebbles completely evaporate and are absorbed before reaching the core, which signifies the end of direct core growth. Methods. We model the early growth of a protoplanet by calculating the structure of its envelope, taking into account the fate of impacting pebbles or planetesimals. The region where high-Z material can exist in vapor form is determined by the temperature-dependent vapor pressure. We include enrichment effects by locally modifying the mean molecular weight of the envelope. Results. In the pebble case, three phases of core growth can be identified. In the first phase (Mcore < 0.23–0.39 M⊕), pebbles impact the core without significant ablation. During the second phase (Mcore < 0.5M⊕), ablation becomes increasingly severe. A layer of high-Z vapor starts to form around the core that absorbs a small fraction of the ablated mass. The rest of the material either rains out to the core or instead mixes outwards, slowing core growth. In the third phase (Mcore > 0.5M⊕), the high-Z inner region expands outwards, absorbing an increasing fraction of the ablated material as vapor. Rainout ends before the core mass reaches 0.6 M⊕, terminating direct core growth. In the case of icy H2O pebbles, this happens before 0.1 M⊕. Conclusions. Our results indicate that pebble accretion can directly form rocky cores up to only 0.6 M⊕, and is unable to form similarly sized icy cores. Subsequent core growth can proceed indirectly when the planet cools, provided it is able to retain its high-Z material.

Modular Synthesis of γ-Valerolactone-Based Ionic Liquids and Their Application as Alternative Media for Copper-Catalyzed Ullmann-type Coupling Reactions

A convenient procedure was developed for the manufacturing of partially bio-ionic liquids (ILs) from renewable γ-valerolactone (GVL) and cheap and readily available tetraalkylphosphonium bromides with excellent (>99%) yields. The novel ionic liquids were characterized by their temperature dependent vapor pressure, density, viscosity, and conductivity. We have proven that these ILs can be a useful medium for copper-catalyzed Ullmann-type coupling reactions without the use of any ligand or additive, representing an environmentally benign tool for the synthesis of various amines. Twenty cross-coupling products were isolated with good to excellent yields (50–87%).

Renewable platform chemicals: Thermochemical study of levulinic acid esters

Abtract Equilibrium of the levulinic acid esterification with methanol, ethanol, and 1-butanol was studied in a broad temperature range (323 K–473 K) for reactions catalyzed by the enzyme Novozym 435 as well as for uncatalysed reaction systems. Thermodynamic equilibrium constants were derived with help of activity coefficients of reaction participants, which were predicted with the equation of state PC-SAFT. The liquid phase standard molar enthalpies of formation of methyl-, ethyl-, and n-butyl-esters of levulinic acid were measured by using the high-precision combustion calorimetry. Vapor pressures of these esters were measured by using the transpiration method. The standard molar enthalpies of vaporization of alkyl levulinates at 298.15 K were derived from vapor pressure temperature dependencies. Thermochemical data of alkyl levulinates were collected, evaluated, and tested for internal consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas phase enthalpies of formation of studied esters. Thermodynamic analysis of the levulinic acid esterification has been performed. Using the levulinic acid esterification with alcohols as the model reaction for an industrial processing of biomass conversion to fuels and useful platform chemicals, we have shown that qualitatively correct agreement between results from equilibrium study, from thermochemical data (combustion and transpiration), and from G4 calculations was observed. Reasonable combination of the quantum-chemical methods and of PC-SAFT modelling with empirical methods could serve to reduce experimental efforts for assessment of feasibility of the chemical processes of utilization of renewable feedstocks.

Synthesis, crystal structure and vapour pressure studies of novel nickel complex as precursor for NiO coating by metalorganic chemical vapour deposition technique

A square planar nickel complex namely bis(N-propyl-3-methylsalicylaldimine)nickel(II) (2) was prepared from its parent compound bis(3-methylsalicylaldehydato)nickel(II) (1) by adding n-propylamine in a methanol medium. The TG/DTA analysis of the resultant Schiff's base complex 2 in the solid phase was evaluated in an inert N2 environment at atmospheric pressure. Complex 2 was completely volatile giving nil residue at 335 °C in a single weight loss step, whereas the complex 1 was found to be non-volatile giving 47% residues till 455 °C. The change in volatility of 2 was brought about by the condensation of n-propylamine with 1 which replaced aldehyde O (-CH=O) with N (-CH=N). The volatile precursor 2 was characterised by single crystal XRD, 1H and 13C NMR, FT-IR, C, H and N elemental analysis and mass spectrometry. The temperature dependence of the saturated vapour pressure and enthalpy of vapourisation (ΔvapH° = 97.9 ± 2.0 kJ mol−1) of the volatile complex 2 was determined by a transpiration TG technique in the temperature range 499–562 K. Subsequently, it was used as a precursor for the deposition of nickel oxide (NiO) thin film on Si(100) substrate by employing plasma assisted metal-organic chemical vapour deposition (PAMOCVD) technique. The nano-crystalline nickel oxide thin films were analysed by XRD and SEM/EDX. X-ray photoelectron spectroscopy (XPS) study confirmed the formation of stoichiometric NiO phase. The band gap of the NiO thin film was found to be 4.31eV exhibiting a blue shift as observed from DRS-UV.

Alkyl-imidazolium tetrafluoroborates: Vapor pressure, thermodynamics of vaporization, and enthalpies of formation

The absolute vapor pressures for the series of [Cnmim][BF4] ionic liquids with (n=2, 4, 6, 8, and 10) were measured over the temperature range 404–457K by using the quartz-crystal microbalance. An absence of possible thermal decomposition was monitored by the ATR-IR spectroscopy. The molar enthalpies of vaporization of ionic liquids under study were derived from vapor pressure temperature dependences and adjusted to the reference temperature 298.15K. The liquid phase molar enthalpy of formation of [C2mim][BF4] was derived from the solution calorimetry and combined with its molar vaporization enthalpy to get the first experimental gas-phase molar enthalpy of formation of the [BF4]− containing ionic liquid. A computational approach based on the DLPNO-CCSD(T) method was used to calculate the theoretical gas-phase molar enthalpy of formation of [C2mim][BF4]. The theoretical and experimental results were found to be in agreement within the combined uncertainties, providing the mutual validation of experimental and computational procedures used in the current study.

Aliphatic nitroalkanes: Evaluation of thermochemical data with complementary experimental and computational methods

Thermochemical properties of aliphatic nitroalkanes available in the literature are scarce and inconsistent. New standard molar enthalpies of vaporization and sublimation of 2-nitropropane, 2-methyl-2-nitropropane, and 2,3-dimethyl-2,3-dinitrobutane were derived from the vapor pressure temperature dependence measured by the transpiration method. Thermodynamic data on linear and branched aliphatic mono- and di-nitroalkanes available in the literature were combined with own experimental results and evaluated with help of empirical and theoretical methods aiming at recommendation of the sets of vaporization and formation enthalpies for aliphatic nitroalkanes as the reliable benchmark properties for further thermochemical calculations. Gas phase standard molar enthalpies of formation of aliphatic nitro-compounds derived by high-level quantum-chemical method G4 were found in a good agreement with the evaluated and recommended experimental data. Group-additivity procedure for calculation of vaporization and formation enthalpies have been developed and tested.

Thermodynamic characterization of Ni3TeO6, Ni2Te3O8 and NiTe2O5

Measurement of vapour pressure of TeO2(g) over the biphasic mixture Ni3TeO6 (s) + NiO(s) in the temperature range 1143–1272 K was carried out using transpiration-thermogravimetric technique (TTG). Gibbs energy of formation of Ni3TeO6 was obtained from the temperature dependence of vapour pressure of TeO2 (g) generated by the incongruent vapourisation reaction, Ni3TeO6 (s) → NiO(s) + TeO2 (g) + 12 O2 in the temperature range 1143–1272 K. An isoperibol type drop calorimeter was used to measure the enthalpy increments of Ni3TeO6, Ni2Te3O8 and NiTe2O5. Thermodynamic functions viz., heat capacity, entropy and Gibbs energy functions of these compounds were derived from the experimentally measured enthalpy increment values. Third-law analysis was carried out to ascertain absence of temperature dependent systematic errors in the measurement of vapour pressure of TeO2 (g). A value of −1265.1 ± 1.5 kJ mol−1 was obtained for ΔHf,298Ko (Ni3TeO6) using third-law analysis.

Thermal behavior of methoxy-substituted Pd and Cu β-diketonates and their heterobimetallic complex

The thermal behavior of volatile heterometallic CuPdL4 compound and parent β-diketonate complexes CuL2 and PdL2 (L = 2-methoxy-2,6,6-trimethylheptane-3,5-dionate; (CH3)3CCOCHCOC(CH3)2OCH3) were investigated by different methods. It is demonstrated that the combination of data on the gradient sublimation, TG–DTA, the mass transfer in a stream of inert gas and mass spectrometry can determine the composition of the gas phase. The volatility of the heterometallic complex was shown to follow the vapor-phase composition presented by binuclear [CuL2PdL2] molecules, and there was no decomposition into monometallic complexes within the studied temperature range (403–438 K). Temperature dependences of the saturated vapor pressure were obtained, and thermodynamic parameters of the sublimation process were computed for these three compounds for the first time. The thermal decomposition of the bimetallic complex vapor was found to start with the surface reaction of dissociation into monometallic complexes followed by their thermolysis with the formation of Cu/Pd alloy films.

Benchmarking thermochemical experiments and calculations of nitrogen-containing substituted adamantanes

Standard molar enthalpy of formation of 2-cyano-adamantane was obtained by using high-precision combustion calorimetry. The standard molar enthalpies of sublimation of 2-cyano-adamantane and 2,2-dinitro-adamantane at 298.15 K were derived from the vapor pressure temperature dependences measured by transpiration. The molar enthalpies of fusion of these compounds were measured with the help of differential scanning calorimetry. Thermochemical data on functional substituted adamantanes containing nitrogen in the substituents were collected and evaluated. The gas-phase enthalpies of formation were calculated with the high-level quantum-chemical method G4 and compared with the experimental results. The consistent data set of the benchmark quality was suggested for practical thermochemical calculations. Geminal destabilizing effects for the interactions of nitro- and cyano-substituents placed in the second position on the adamantane cage were derived. Structure–property correlations for substituted adamantanes and aliphatic substituted alkanes were found and suggested for the assessment of the gas-phase enthalpies of formation of adamantane derivatives.

A compact form for the analytic description of temperature dependence of saturation vapor pressure over plane surfaces of water and ice

A possibility is studied of extending the range of action of the simple three-parameter formula (ITS-90 scale) proposed in the previous work of the author [2] for the dependence of saturation vapor pressure E on temperature T within the range of 250 to 490 K. The results demonstrated that the dependence ln[E(T)/E(T bas)] = (T - T bas)[A - B(T - T bas) + C(T - T bas)2]/T with four sets of coefficients A, B, and C obtained using one base temperature Tbas equal to the temperature of triple point of water T t = 273.16 K and two additional base values T bas2 = 473.16 K and T bas3 = 623.16 K makes it possible to approximate rather accurately the initial experimental and computed data in the temperature range from the point of homogeneous freezing of 235 K to the critical temperature of 647 K for liquid water and from 193 K to T t for ice. A procedure used for obtaining the inverse function T(E) by solving the third-degree algebraic equation is validated. A hypothesis is proposed for the physical substantiation of additional base points in the form of “a noticeable appearance of dimers at the point T bas2 and their 100% concentration at the temperature T bas3.”

Nearest-Neighbor and Non-Nearest-Neighbor Interactions between Substituents in the Benzene Ring. Experimental and Theoretical Study of Functionally Substituted Benzamides.

Standard molar enthalpies of formation of 2- and 4-hydroxybenzamides were measured by combustion calorimetry. Vapor pressures of benzamide and 2-hydroxybenzamide were derived by the transpiration method. Standard molar enthalpies of sublimation or vaporization of these compounds at 298K were obtained from vapor pressure temperature dependence. Thermochemical data on benzamides with hydroxyl, methyl, methoxy, amino, and amide substituents were collected, evaluated, and tested for internal consistency. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas-phase enthalpies of formation. Sets of nearest-neighbor and non-nearest-neighbor interactions between substituents in the benzene ring have been evaluated. A simple incremental procedure has been suggested for a quick appraisal of the vaporization and gas-phase formation enthalpies of the substituted benzamides.