Group-contribution Methodology Research Articles

A robust and efficient solution for COSMO-based activity coefficient models

COSMO-based activity coefficient models, such as COSMO-RS and COSMO-SAC, offer a powerful tool that bridges quantum chemical calculations with macroscopic phase equilibrium calculations. These models utilize a group contribution methodology similar to UNIFAC but require an expensive numerical solution of the self-consistency equation for interactions among all surface segments, representing a primary bottleneck in their application to analyses that involve extensive phase equilibrium calculations. This work demonstrates that the self-consistency equation can be derived by minimizing the system energy from all pairwise segment interactions. The derivation leads to an optimization-based second-order solution procedure that ensures convergence and enhances efficiency. We demonstrate the robustness and efficiency of the proposed solution using various examples, including a comparison with the classical successive substitution method, and illustrate that COSMO-based models can be coupled with modern second-order convergent algorithms for phase equilibrium calculations. Furthermore, this work reveals the similarity between COSMO-based models and the SAFT method.

Comprehensive thermodynamic modeling framework for the estimation of physico-chemical properties of deep eutectic solvent-heavy crude oil system

Physico-chemical properties such as density, solubility parameter, viscosity, volume change on mixing and surface tension for pure deep eutectic solvent (DES), heavy crude oil (saturate, aromatic, resin and asphaltene i.e. SARA) and DES-SARA mixtures are estimated. The models are established considering the variation of SARA from three geographic locations and five DESs from hydrophilic and hydrophobic nature. Further, variation in temperature and concentration of DESs or SARA are explicitly considered. The structural variations are incorporated by estimating the critical properties in Lydersen–Joback–Reid framework using group contribution methodology. Cohesion based equation of state is used to estimate the density of SARA and DES. Geometric similitude concept in conjunction with cubic equation of state is used to estimate the surface tension and viscosity of DES and SARA. Later six different formulations namely, Arrhenius, Power law model, Lobe, Cragoe, Double-log, and Lederer model are employed to calculate the mixture viscosity of DES-SARA system.

Artificial neural network for the prediction of physical properties of organic compounds based on the group contribution method

AbstractIn the development and optimization of chemical processes involving the selection of organic fluids, knowledge of the physical properties of compounds is vital. In many cases, it is complex to find experimental measurements for all substances, so it becomes necessary to have a tool to predict properties based on the characteristics of the molecule. One of the most extensively used methods in the literature is the estimation by contribution of functional groups, where properties are calculated using the constituent elements of the molecule. There are several models published in the literature, but they fail to represent a wide variety of compounds with high accuracy and simultaneously maintain a low computational complexity. The aim of this work is to develop a prediction model for eight thermodynamic properties (melting temperature, boiling temperature, critical pressure, critical temperature, critical volume, enthalpy of vaporization, enthalpy of fusion, and enthalpy of gas formation) based on the group contribution methodology by implementing a multilayer perceptron. Here, 2736 substances were used to train the neural network, whose prediction capacity was compared with other reference models available in the literature. The proposed model presents errors ranging from 1% to 5% for the different properties (except for the melting point), which improves the reference models with errors in the range of 3%–30%. Nevertheless, a difficulty in the prediction of the melting point is detected, which could represent an inherent hindrance to this methodology.

MultiTFA: a Python package for multi-variate thermodynamics-based flux analysis.

MotivationWe achieve a significant improvement in thermodynamic-based flux analysis (TFA) by introducing multivariate treatment of thermodynamic variables and leveraging component contribution, the state-of-the-art implementation of the group contribution methodology. Overall, the method greatly reduces the uncertainty of thermodynamic variables.ResultsWe present multiTFA, a Python implementation of our framework. We evaluated our application using the core Escherichia coli model and achieved a median reduction of 6.8 kJ/mol in reaction Gibbs free energy ranges, while three out of 12 reactions in glycolysis changed from reversible to irreversible.Availability and implementationOur framework along with documentation is available on https://github.com/biosustain/multitfa.Supplementary informationSupplementary data are available at Bioinformatics online.

A New Predictive Group-Contribution Ideal-Heat-Capacity Model and Its Influence on Second-Derivative Properties Calculated Using a Free-Energy Equation of State

A statistical-thermodynamics-based group contribution (GC) method, commensurate with the GC methodology used in SAFT-γ Mie, is proposed to model ideal heat capacities. Special treatment of halogenated groups allows many halogenated molecules to be modeled with few parameters. Parameters for small, single-group species agree well with experimental vibrational temperatures. Parameters corresponding to groups used for larger species highlight effects such as anharmonicity and torsional modes. The proposed correlation consistently demonstrates higher accuracy than that of Joback and Reid. Ideal heat capacities are seldom used in isolation, but contribute to other properties that may be used to assess the quality of an equation of state. The importance of the ideal free energy to various second-derivative properties, as calculated using the SAFT-γ Mie equation of state, is examined. In the majority of cases, using the proposed correlation to calculate the ideal free energy results in more-accurately estimated second-derivative properties—sometimes substantially so. Further studies of the contribution of the ideal free energy are carried out revealing interesting behavior near the critical point that may relate to the Widom-Fisher and Widom lines.

Estimation of dual mode sorption parameters for CO2 in the glassy polymers using group contribution approach

The solubility of gases in glassy polymers plays a fundamental role in permeability and selectivity for membrane separation. This study correlates the sorption data of CO2 in glassy polymers to the polymer structure, using group contribution (GC) approach, to predict the dual-mode sorption (DMS) model parameters. This procedure has been utilized to determine the contributions of 37 structural units employing a wide variety of polymers of industrial interest which comprise the database. An excellent agreement between the experimental and predicted values for DMS parameters within the database is observed. Moreover, the experimental data for sorption of CO2 in six different polymers outside the database are also considered. The results show good predictability of DMS parameters of CO2 in these six glassy polymers so that the mean relative errors between the experimental and predicted values for kD, CH' and b are 9, 9 and 18%, respectively. Hence, the results indicate that the GC methodology can be applied to predict the polymer solubility. This approach allows to incorporate the structure/solubility quantitative relationships of desired polymers to design of membrane separation processes.

Extensive Databases and Group Contribution QSPRs of Ionic Liquids Properties. 1. Density

A new group contribution (GC) quantitative structure-property relationship (QSPR) for estimating density (ρ) of pure ionic liquids (ILs) as a function of temperature (T) and pressure (p) is developed on the basis of the most comprehensive collection of volumetric data reported so far (in total 41 250 data points, deposited for 2267 ILs from diverse chemical families). The model was established based on a carefully revised, evaluated, and reduced data set, whereas the adopted GC methodology follows the approach proposed previously [ Ind. Eng. Chem. Res. 2012, 51, 591−604]. However, a novel approach is proposed to model both temperature and pressure dependence. The idea consist of an independent representation of reference density ρ0 at T0 = 298.15 K and ρ0 = 0.1 MPa and dimensionless correction f(T, P) ≡ ρ(T, p)/ρ0 for other conditions of temperature and pressure. Three common machine learning algorithms are employed to represent the quantitative structure–property relationship between the studied property...

Further development of the predictive models for physical properties of pure ionic liquids: Thermal conductivity and heat capacity

Abstract Efficient, fast and accurate heat transfer units design is currently a ‘hot topic’ due to the demand for more approachable and high-performance-ability materials. This is usually performed by the prediction of physical properties coupled with sufficient structure searching (for example with genetic algorithm). Ionic liquids have been found to be prospective replacement materials in this case; however, the predictive capabilities of existing models still remain poor which affects their practical application significantly. It has also been observed that for some quaternary-phosphonium based carboxylate ILs, the models fail, particularly, for thermal conductivity and heat capacity predictions. The impact of electronic structure on the heat capacity was confirmed by DFT calculations, and this was also included in further refinement. The aim of this work is to assess the predictive capabilities of existing models for thermal conductivity and heat capacity, with further improvements based on more accurate investigated structure characterization (DFT) and reparameterization (group contribution methodology). The ILs chosen for the initial study are trihexyl(tetradecyl)phosphonium-based carboxylate derivatives.

COSMO-descriptor based computer-aided ionic liquid design for separation processes. Part I: Modified group contribution methodology for predicting surface charge density profile of ionic liquids

When applying COSMO-based models in Computer-Aided Ionic Liquid Design (CAILD), the generation of surface charge density profiles (σ-profiles) and cavity volumes (VCOSMO) of ILs is particularly important but too computationally expensive with quantum chemical calculations. In this work, a modified group contribution methodology, the COSMO-GC-IL method, is proposed for quick prediction of IL σ-profiles and VCOSMO based on σ-profiles of IL groups in their reference states (COSMO descriptors), together with two modification parameters (stretch and translation parameters). The influence of molecular environment on target groups can be well described and IL isomers are thereby distinguishable. To verify the method, σ-profiles and VCOSMO generated from the present method and from the DMol3 database are employed to calculate activity coefficients of 28,644 binary systems and 3410 liquid-liquid equilibria of ternary mixtures. Their close results in most cases demonstrate the reliability of the COSMO-GC-IL method.

The development of unlike induced association-site models to study the phase behaviour of aqueous mixtures comprising acetone, alkanes and alkyl carboxylic acids with the SAFT-γ Mie group contribution methodology

Providing accurate predictions of the thermodynamic properties of highly polar and hydrogen bonding compounds and their mixtures is challenging from a theoretical perspective. The combination of an equation of state (EoS) based on the statistical associating fluid theory (SAFT) with a group contribution (GC) methodology offers both accuracy and predictive capability for the thermodynamic properties of mixtures. In our current work, the SAFT-γ Mie equation of state is used to capture the underlying complexity of systems in which specific interactions (e.g. hydrogen bonding, dipolar interactions, chemical association) play an important role, by incorporating highly versatile association-site schemes to model mixtures in which unlike induced association interactions occur; this is done by assigning to the functional groups a number of association sites that are inactive in the pure fluid, but become active in certain mixtures. We refer to this type of association mechanism as “unlike induced” association and to the sites involved in this interaction as “unlike induced” association sites. The concept of unlike induced association sites is applied here to develop reliable SAFT-γ Mie group contribution models to describe the properties of acetone, alkyl carboxylic acids, and their mixtures with water and n-alkanes. The parameter table of available SAFT-γ Mie models is expanded to incorporate the corresponding group interaction parameters for acetone, which is treated as a molecular group, the carboxyl group COOH, and their unlike interaction group parameters with water, and the methyl CH3, methanediyl CH2, and methanetriyl CH alkyl groups. In particular, one unlike induced site is used with the acetone model to mediate hydrogen bonding of the acetone oxygen in mixtures containing hydrogen bond donors, and two pairs of unlike induced sites are included on the COOH group to mediate hydrogen bond formation in mixtures of carboxylic acids and hydrogen bond donors. The models developed allow for the successful description of the complex fluid-phase behaviour of the relevant binary and ternary mixtures, including accurate predictions of systems which have not been used to determine the model parameters.

Prediction of Thermodynamic Properties and Phase Behavior of Fluids and Mixtures with the SAFT-γ Mie Group-Contribution Equation of State

Group contribution (GC) approaches are based on the premise that the properties of a molecule or a mixture can be determined from the appropriate contributions of the functional chemical groups present in the system of interest. Although this is clearly an approximation, GC methods can provide accurate estimates of the properties of many systems and are often used as predictive tools when experimental data are scarce or not available. Our focus is on the SAFT-γ Mie approach [Papaioannou, V.; Lafitte, T.; Avendaño, C.; Adjiman, C. S.; Jackson, G.; Müller, E. A.; Galindo, A. Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments. J. Chem. Phys. 2014, 140, 054107–29] which incorporates a detailed heteronuclear molecular model specifically designed for use as a GC thermodynamic platform. It is based on a formulation of the recent statistical associating fluid theory for Mie potentials of variable range, where a formal statistical–mechanical perturbation theory is used to maintain a firm link between the molecular model and the macroscopic thermodynamic properties. Here we summarize the current status of the SAFT-γ Mie approach, presenting a compilation of the parameters for all functional groups developed to date and a number of new groups. Examples of the capability of the GC method in describing experimental data accurately are provided, both as a correlative and as a predictive tool for the phase behavior and the thermodynamic properties of a broad range of complex fluids.

Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments

A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative properties of compounds not included in the development of group parameters are demonstrated. The performance of the theory is also critically assessed with predictions of the fluid-phase behavior (vapor-liquid and liquid-liquid equilibria) and excess thermodynamic properties of a variety of binary mixtures, including polymer solutions, where very good agreement with the experimental data is seen, without the need for adjustable mixture parameters.

SAFT-γ Force Field for the Simulation of Molecular Fluids: 2. Coarse-Grained Models of Greenhouse Gases, Refrigerants, and Long Alkanes

In the first paper of this series [C. Avendaño, T. Lafitte, A. Galindo, C. S. Adjiman, G. Jackson, and E. A. Müller, J. Phys. Chem. B2011, 115, 11154] we introduced the SAFT-γ force field for molecular simulation of fluids. In our approach, a molecular-based equation of state (EoS) is used to obtain coarse-grained (CG) intermolecular potentials that can then be employed in molecular simulation over a wide range of thermodynamic conditions of the fluid. The macroscopic experimental data for the vapor-liquid equilibria (saturated liquid density and vapor pressure) of a given system are represented with the SAFT-VR Mie EoS and used to estimate effective intermolecular parameters that provide a good description of the thermodynamic properties by exploring a wide parameter space for models based on the Mie (generalized Lennard-Jones) potential. This methodology was first used to develop a simple single-segment CG Mie model of carbon dioxide (CO2) which allows for a reliable representation of the fluid-phase equilibria (for which the model was parametrized), as well as an accurate prediction of other properties such as the enthalpy of vaporization, interfacial tension, supercritical density, and second-derivative thermodynamic properties (thermal expansivity, isothermal compressibility, heat capacity, Joule-Thomson coefficient, and speed of sound). In our current paper, the methodology is further applied and extended to develop effective SAFT-γ CG Mie force fields for some important greenhouse gases including carbon tetrafluoride (CF4) and sulfur hexafluoride (SF6), modeled as simple spherical molecules, and for long linear alkanes including n-decane (n-C10H22) and n-eicosane (n-C20H42), modeled as homonuclear chains of spherical Mie segments. We also apply the SAFT-γ methodology to obtain a CG homonuclear two-segment Mie intermolecular potential for the more challenging polar and asymmetric compound 2,3,3,3-tetrafluoro-1-propene (HFO-1234yf), a novel replacement refrigerant with promising properties. The description of the fluid-phase behavior and the prediction of the other thermophysical properties obtained by molecular simulation using our SAFT-γ CG Mie force fields are found to be of comparable quality (and sometimes superior) to that obtained using the more sophisticated all-atom (AA) and united-atom (UA) models commonly employed in the field. We should emphasize that though the focus of our current work is on simple homonuclear models, the SAFT-γ methodology is based on a group contribution methodology which is naturally suited to the development of more sophisticated heteronuclear models.

SAFT-γ force field for the simulation of molecular fluids: 3. Coarse-grained models of benzene and hetero-group models of n-decylbenzene

In the first paper of this series [C. Avendaño, T. Lafitte, A. Galindo, C.S. Adjiman, G. Jackson, and E.A. Müller, J. Phys. Chem. B 115, 11154 (2011)] our methodology for the development of accurate coarse-grained (CG) SAFT-γ force fields for the computer simulation of molecular fluids was introduced with carbon dioxide as a particular case study. The procedure involves the use of a molecular-based equation of state to obtain effective intermolecular parameters (from experimental fluid phase equilibrium data) appropriate for molecular simulation over a wide range of fluid conditions. We now extend the methodology to develop coarse-grained models for benzene (C6H6) that can be used in fluid phase simulations. Our SAFT-γ CG force fields for benzene consist of a simple single-segment spherical model, and a rigid three-segment ring structure of tangent spherical groups interacting via Mie (generalized Lennard-Jones) segment–segment interactions. The description of the fluid phase behaviour of benzene with our simplified CG force fields is found to be comparable to that obtained with the more sophisticated models commonly used in the field; a marked improvement is seen with our SAFT-γ models for the vapour pressure, particularly at lower temperatures. These models of benzene together with the previously developed SAFT-γ three-segment chain model of n-decane are used to develop hetero-group force fields for n-decylbenzene, in the spirit of a group contribution methodology. In our approach, the parameters of the phenyl and n-decyl groups are obtained transferably from the individual models of benzene and n-decane, respectively, and the unlike energetic parameters between the phenyl and decyl segments can be obtained from vapour–liquid equilibria data for n-decylbenzene using the SAFT-γ equation of state. The resulting CG hetero-group models are found to describe the fluid properties of n-decylbenzene over a wide range of conditions, exemplifying how our approach can be used as a group contribution methodology. This is the first example of the development of hetero-group SAFT-γ force fields for molecules formed from Mie segments of different size, energy, softness/hardness, and range.

Thermochemistry of Drugs. Experimental and First-Principles Study of Fenamates

This work has been undertaken to obtain new thermochemical data for diphenylamine and its derivatives to improve the group contribution methodology for the prediction of the thermodynamic properties of the biologically active compounds. Standard molar enthalpies of formation in the gaseous state of diphenylamine and N-phenylanthranilic acid have been obtained from combustion calorimetry and results from the temperature dependence of the vapor pressure measured by the transpiration method. To verify the experimental data, first principles calculations of all compounds have been performed. Enthalpies of formation derived from G3MP2 method and the bond separation procedure are in good agreement with the experimental results.

Thermochemical and Ab Initio Studies of Biodiesel Fuel Surrogates: 1,2,3-Propanetriol Triacetate, 1,2-Ethanediol Diacetate, and 1,2-Ethanediol Monoacetate

This work has been undertaken to obtain new thermochemical data for ethanediol and propanetriol acetates and to improve the group contribution methodology for the prediction of the thermodynamic properties of compounds relevant to biodiesel. Standard molar enthalpies of formation in the gaseous state of a series of 1,2-ethanediol monoacetate, 1,2-ethanediol diacetate, and 1,2,3-propanetriol triacetate have been obtained from combustion calorimetry and results from the temperature dependence of the vapor pressure measured by the transpiration method. To verify the experimental data, ab initio calculations of all compounds have been performed. Enthalpies of formation derived from the Gaussian 03 second-order Moller−Plesset (G3MP2) method are in good agreement with the experimental results. The strength of the hydrogen bond in 1,2-ethanediol monoacetate and in 1,2-ethanediol have been obtained using ab initio calculations and the group additivity method.

Group Contribution Prediction of Vapor Pressure with Statistical Associating Fluid Theory, Perturbed-Chain Statistical Associating Fluid Theory, and Elliott−Suresh−Donohue Equations of State

The group contribution methodology developed by Elliott and Natarajan has been extended to the statistical associating fluid theory (SAFT) and perturbed-chain statistical associating fluid theory (PC-SAFT) equations of state (EOS). Thermodynamic properties were correlated and predicted for a database of 878 compounds, including associating compounds. Association contributions were treated with Wertheim’s theory. The database covers 19 chemical families including hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, alcohols, amines, nitriles, thiols, sulfides, aldehydes, ketones, esters, ethers, halocarbons, and silicones. The present group contribution (GC) method was developed in two stages. Initially, pure component parameters of each EOS were obtained by matching their boiling temperatures at 10 or 760 mmHg and available GC estimates of solubility parameter and liquid density, while applying standard hydrogen-bonding parameters. Then, group contributions were regressed for the shape factor parameters of each EOS. Group contributions are presented for 84 first-order functional groups (FOG). Given the GC shape factors, the same GC estimates of solubility parameter and liquid density can be applied to estimate all EOS parameters on a GC basis. The resulting correlation enables three-parameter corresponding states predictions without any experimental data. A byproduct of the correlation for equation of state parameters is the capability to predict vapor pressure only on the basis of chemical structure. This capability was evaluated by computing the vapor pressures at 10, 100, and 760 mmHg. On the basis of the present work, vapor pressure average absolute percent deviations (P AAD%) were 36% for Elliott−Suresh−Donohue (ESD) EOS, 65% for SAFT, 32% PC-SAFT. For comparison, the first- and second-order groups (FOG and SOG) provided by Tihic et al. (for simplified PC-SAFT) have been applied to ∼650 nonassociating compounds. The resulting P AAD% were 53% for Tihic FOG and 42% for Tihic SOG. An alternative characterization of accuracy is the average absolute deviation (|ΔT|) between experimental and calculated saturated temperature. These were 8, 12, 8, 10, and 9 K for ESD, SAFT, PC-SAFT, Tihic FOG, and Tihic SOG equations, respectively.

Structure−Energy Relationships in Unsaturated Esters of Carboxylic Acids. Thermochemical Measurements and ab Initio Calculations

Standard molar enthalpies of formation in the gaseous state of a series of alkyl 3-methylbut-2-enoates have been obtained from combustion calorimetry and results from the temperature dependence of the vapor pressure measured by the transpiration method. To verify the experimental data, we have performed ab initio calculations of all compounds. Enthalpies of formation derived from the G3MP2 method are in excellent agreement with the experimental results. Quantitative analysis of strain effects in alkyl 3-methylbut-2-enoates was discussed in terms of deviations of deltafH degrees m(g) from the group additivity rules. Energetics of the cis-trans isomerization of carboxylic acid derivatives was studied using G3MP2 and DFT methods. Values of strain and cis-trans corrections derived in this work provide further improvement on the group-contribution methodology for prediction of the thermodynamic properties of compounds relevant to biodiesel.

Nonequilibrium nanoblend membranes for the pervaporation of benzene/cyclohexane mixtures

AbstractImmiscible blends of polymers were cast from solution, and the rate of evaporation was controlled relative to the rate of phase separation to produce different morphologies; upon crosslinking, stable nonequilibrium nanoblends were realized. This process of forced assembly produced useful membrane materials that could be designed for solubility selectivity with the group contribution methodology. Crosslinked ternary blends of nitrile butadiene rubber (NBR), poly(methyl methacrylate) (PMMA), and a tercopolymer of ethylene oxide/epichlorohydrin/allyl glycidyl ether (Hydrin) were examined for use in the separation of benzene from cyclohexane by pervaporation. For a 50 : 50 wt % benzene/cyclohexane feed, blend 811 (containing 80 wt % NBR, 10 wt % Hydrin, and 10 wt % PMMA) gave a separation factor of 7.3 and a normalized flux of 28 kg μm/m2 h; such a performance is unmatched in the literature, with the flux being very high for the reported separation factor. Among the samples tested, the flux of the membrane increased as the amount of NBR in the ternary blend decreased; however, the separation factor was not largely affected. Blended samples showed no sign of deformation after 48 h at the operating temperature as compared to pure NBR, which did show evidence of creep. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Thermodynamic Properties and Ideal-Gas Enthalpies of Formation for trans-Methyl Cinnamate, α-Methyl Cinnamaldehyde, Methyl Methacrylate, 1-Nonyne, Trimethylacetic Acid, Trimethylacetic Anhydride, and Ethyl Trimethyl Acetate

The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric heat-capacity measurements. Ideal-gas and condensed-phase enthalpies of formation of trans-methyl cinnamate, α-methyl cinnamaldehyde, methyl methacrylate, 1-nonyne, trimethylacetic acid, trimethylacetic anhydride, and ethyl trimethyl acetate are reported. Enthalpies of fusion were determined for trans-methyl cinnamate and trimethylacetic acid. Two-phase (solid + vapor) or (liquid + vapor) heat capacities were determined from 300 K to the critical region or earlier decomposition temperature for all the compounds. For ethyl trimethyl acetate, the values of the critical temp...