(672f) Position Group Contribution Method for the Prediction of the Fusion Enthalpy of Organic Compounds

Abstract Recently, authors have proposed a position group contribution method for the prediction of critical and other thermodynamics parameters of organic compounds with a similar framework. The objective of this work was to develop and evaluate our new position group contribution method for predicting the fusion enthalpy of a variety of pure organic compounds. Comparison results between experimental and calculated data indicate that our model provides very satisfactory results. The overall average absolute errors for the fusion enthalpy predictions of 291 organic compounds is 3.33 kJ/mol and 20.9 % means absolute relative derivation. Also, good prediction of the proposed method shown in our previous works and this work further demonstrated the universality of our proposed method. Keywords: Fusion enthalpy; Prediction; Position distribution function Introduction The fusion enthalpy is an important physical property of the solid state, and can be useful in correcting thermo-chemical data to a standard state when combined with other thermodynamic properties. However, the reliable experimental fusion enthalpy data available is very limited, so it is necessary to develop techniques for estimating the fusion enthalpy. Firstly, fusion enthalpies could be calculated or estimated by its definition. James S. Chickos et al. suggested that fusion enthalpy estimations based solely on molecular structure could expect only limited success[1-4]. Consequently, they focused attention on developing an additivity method for estimating fusion entropies, then, by combination of the experimental melting point with the estimated entropy of fusion, fusion enthalpies could be estimated. However, the need for the melting temperature significantly limits the applicability and reliability of such technique, as experimental values of the melting temperature may not be available. It is well-known that the fusion enthalpy can be predicted with reasonable accuracy by various group contribution (GC) schemes [5-7]. Joback and Reid [5] proposed simple GC methods to estimate eleven important physical properties (including the fusion enthalpy) of pure materials. Based on Constantinou et al.'s [8] second-order group contribution method, Marrero and Gani [9] proposed their third-order GC method to the estimation of the fusion enthalpy for a variety of organic compounds. Recently, wang et al. [10-13] proposed a position group contribution method for the prediction of critical and other thermodynamics parameters of organic compounds with a similar framework and the proposed method performed well both in accuracy and generality. Therefore, the purpose of this study was to determine whether our proposed position group contribution method could be used directly for fusion enthalpy estimation. For this purpose, 291organic compounds from literature were selected, and the performance of our new model had been compared with the method of Joback and Reid. Method proposed in this work Experimental data The sources of experiment data were from DIPPR database [14] and the handbook of ma[15]. When all the groups' contribution value have been determined, the recommended 291 experiment data from the literature was used to validate and evaluate the performance of our new method. The position group contributions for the fusion enthalpy The fusion enthalpy function is constructed by all groups' contribution as well as the position distribution factor. The position distribution factor were used to take into account longer distance interactions. The molecule structures were described according to the IUPAC nominating method, and thus, the only position distribution factor values could be obtained for the relevant positional correction factor , which could distinguish all isomers include cis- and trans- or Z- and E- structure of organic compounds for their thermodynamics properties. Here, the position distribution function for the fusion enthalpy estimation is expressed as eq 1 and eq 2. Comparison method Joback and Reid proposed a simple GC method to the estimation of the fusion enthalpy for a variety of organic compounds (shown as eq(3)). Results and discussion Results presented in Fig.1 indicate that the predicted the fusion enthalpy agree well with the ?experimental results?, which demonstrates that our new position group contribution method for predicting the fusion enthalpy has good overall accuracy. The AAD (overall average absolute errors) for the fusion enthalpy prediction of 291 organic compounds is 3.33 kJ/mol and the mean absolute relative derivation is 20.9 %. Also, results show that our new simple model gives lower deviations and can be used with confidence in thermodynamic and engineering calculations. In addition, the performance of the our model has been compared with the estimation method of Joback and Reid. And the results show that the proposed method is more accurate than Joback and Reid's method for the fusion enthalpy prediction. Conclusion The objective of this work was to develop and evaluate our new position group contribution method for predicting the fusion enthalpy. In this study, contributions for compounds containing carbon, hydrogen, oxygen, nitro¬gen, chlorine and sulphur were reported, and that position distribution function has been developed which could distinguish between the thermodynamic properties of all isomers of organic compounds including cis- and trans- or Z- and E- structures. The results indicate that our model provides very satisfactory results. The overall average absolute difference and the relative derivation for the fusion enthalpy predictions of 291 organic compounds are found to be 3.33 kJ/mol and 20.9 %, respectively. More importantly, the higher prediction accuracy of the proposed method shown in our previous works and this work suggests that it is possible to use a similar framework to predict not only the critical properties, but also fusion enthalpy of organic compounds containing various functional groups, which further demonstrated the universality of our proposed method. Acknowledgement. Thanks for the fund support of the National Natural Science Foundation of China (No. 20976131) Literature Cited 1. James S. Chickos, Donald G. Hesse，Joel F. Liebman, Estimating Entropies and Enthalpies of Fusion of Hydrocarbons，J. Org. Chem. 1990, 55, 3833-3840 2. James S. Chickos, C. Marie Braton, Donald G. Hesse，Joel F. Liebman，Estimating Entropies and Enthalpies of Fusion of Organic Compounds，J. Org. Chem. 1991, 56, 927-938 3. James S. Chickos Gary Nichols, Paul Ruelle, The Estimation of Melting Points and Fusion Enthalpies Using Experimental Solubilities, Estimated Total Phase Change Entropies, and Mobile Order and Disorder Theory, J. Chem. Inf. Comput. Sci. 2002, 42, 368-374 4. James S. Chickos, William E. Acree Jr, Total phase change entropies and enthalpies. An update on fusion enthalpies and their estimation, Thermochimica Acta 2009, 495, 5?13 5. Joback, K. G.; Reid, R. C. Estimation of Pure-Component Properties from Group-Contributions. Chem. Eng. Commun. 1987, 57, 233-243 6. 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