Dataset Information

Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method.

ABSTRACT: The calculation of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, applying a universal computer algorithm based on the atom-groups additivity method, using refined atom groups. The atom groups are defined as the molecules' constituting atoms and their immediate neighbourhood. In addition, the hydroxy group of alcohols are further subdivided to take account of the different intermolecular interactions of primary, secondary, and tertiary alcohols. The evaluation of the groups' contributions has been carried out by solving a matrix of simultaneous linear equations by means of the iterative Gauss-Seidel balancing calculus using experimental data from literature. Plausibility has been tested immediately after each fitting calculation using a 10-fold cross-validation procedure. For the heat capacity of liquids, the respective goodness of fit of the direct (r2) and the cross-validation calculations (q2) of 0.998 and 0.9975, and the respective standard deviations of 8.24 and 9.19 J/mol/K, together with a mean absolute percentage deviation (MAPD) of 2.66%, based on the experimental data of 1111 compounds, proves the excellent predictive applicability of the present method. The statistical values for the heat capacity of solids are only slightly inferior: for r2 and q2, the respective values are 0.9915 and 0.9874, the respective standard deviations are 12.21 and 14.23 J/mol/K, and the MAPD is 4.74%, based on 734 solids. The predicted heat capacities for a series of liquid and solid compounds have been directly compared to those received by a complementary method based on the "true" molecular volume and their deviations have been elucidated.

SUBMITTER: Naef R

PROVIDER: S-EPMC7179130 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method.

Naef Rudolf R

Molecules (Basel, Switzerland) 20200304 5

The calculation of the isobaric heat capacities of the liquid and solid phase of molecules at 298.15 K is presented, applying a universal computer algorithm based on the atom-groups additivity method, using refined atom groups. The atom groups are defined as the molecules' constituting atoms and their immediate neighbourhood. In addition, the hydroxy group of alcohols are further subdivided to take account of the different intermolecular interactions of primary, secondary, and tertiary alcohols. ...[more]

PMID: 32143381

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Project description:The calculation of the standard enthalpies of vaporization, sublimation and solvation of organic molecules is presented using a common computer algorithm on the basis of a group-additivity method. The same algorithm is also shown to enable the calculation of their entropy of fusion as well as the total phase-change entropy of liquid crystals. The present method is based on the complete breakdown of the molecules into their constituting atoms and their immediate neighbourhood; the respective calculations of the contribution of the atomic groups by means of the Gauss-Seidel fitting method is based on experimental data collected from literature. The feasibility of the calculations for each of the mentioned descriptors was verified by means of a 10-fold cross-validation procedure proving the good to high quality of the predicted values for the three mentioned enthalpies and for the entropy of fusion, whereas the predictive quality for the total phase-change entropy of liquid crystals was poor. The goodness of fit (Q²) and the standard deviation (σ) of the cross-validation calculations for the five descriptors was as follows: 0.9641 and 4.56 kJ/mol (N = 3386 test molecules) for the enthalpy of vaporization, 0.8657 and 11.39 kJ/mol (N = 1791) for the enthalpy of sublimation, 0.9546 and 4.34 kJ/mol (N = 373) for the enthalpy of solvation, 0.8727 and 17.93 J/mol/K (N = 2637) for the entropy of fusion and 0.5804 and 32.79 J/mol/K (N = 2643) for the total phase-change entropy of liquid crystals. The large discrepancy between the results of the two closely related entropies is discussed in detail. Molecules for which both the standard enthalpies of vaporization and sublimation were calculable, enabled the estimation of their standard enthalpy of fusion by simple subtraction of the former from the latter enthalpy. For 990 of them the experimental enthalpy-of-fusion values are also known, allowing their comparison with predictions, yielding a correlation coefficient R² of 0.6066.

Project description:Wood bottom and fly ashes were added to the anaerobic digestate using sulfuric, hydrochloric, nitric, and lactic acids, as pH conditioners and sorption activating agents. Minimum (pH of zero-point charge), mild, and severe acidification of the samples were tested. The solid-liquid separation achieved was accounted visually and with the measurement of the masses of water-soluble extract and water-insoluble material isolated. The average mass of the blend was 36.61 ± 0.68 g, including the extractant agent that was prepared with the commercial acids and ultrapure milli-QⓇ water. During the 144-h incubation of the mixtures at 20 °C and 0.17 x g, the shares of the solid and liquid were determined by centrifugation of the destructive samples at 3,130.40 x g for 5 minutes and 3-µm filtration of the supernatant. Before weighing the water-insoluble material, both the pellet that remained in the tube and the filter cake were dried at 70 °C until reaching constant weight. There was a significant increase in the amount of water-insoluble phase of the wood bottom ash due to the activation with lactic and sulfuric acids. The treatment of the wood fly ash and the agrowaste digestate with the hydrochloric acid showed an increase in the formation of water-soluble extract, in direct relation with the acidic pH of the blend. The characterization of the pH of the WS extract was performed with a Mettler ToledoⓇ Seven CompactTM S220 pH/Ion meter. The conditions of this process can be further optimized and each of the fractions can be characterized, in terms of nutrient content, to confirm the efficiency of the separation. More complex and ambitious processes can be designed for combining the wood ash and the anaerobic digestate. The performance of this treatment involving wood ashes and commercial acids can be extrapolated to other type of organic manures with a moisture content of approximately 95%, to improve their management in terms of reducing the cost of storage and transportation for land application below £5 per tonne.

Dataset Information

Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method.

Publications

Calculation of the Isobaric Heat Capacities of the Liquid and Solid Phase of Organic Compounds at 298.15K by Means of the Group-Additivity Method.

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