A New Scheme for Calculating the Standard Enthalpies of Formation of Alkanol Isomers

On the basis of successfully designing the schemes for calculation of the enthalpies of formation of alkane isomers and polychlorocarbon isomers applying the idea of polarity interference, we now design a new scheme for calculating the enthalpies of formation of polyhydric alcohol isomers. In this scheme, we reasonably suppose the enthalpy of atomization of any isomer to be equal to the sum of three bond enthalpy terms (i.e., C-C, C-H and C-O-H bond enthalpy terms) and a polarity interference enthalpy term and a hydrogen bond enthalpy term. Fitting such a model to 24 data of enthalpies of atomization of 24 compounds, an estimation formula for their enthalpies of formation has been obtained. In order to test the prediction accuracy, we have designed a predication method in which using the parameters obtained under exclusion of the compound to be predicted at each time, we predict the enthalpy of formation of the compound. According to such a method, the enthalpies of formation for the 24 isomers have been predicted. The average absolute errors from corresponding experimental values, root mean square deviation, and the max absolute errors predicted by this scheme with 5 parameters are not only much less than those predicted by the group scheme with 7 parameters, but also less than the corresponding deviations of experimental data. Compared with other bond additivity schemes for calculation of the enthalpies of formation of compounds, a very important advantage of this new scheme is that its model contains the polarity interference enthalpy and hydrogen bond enthalpy terms well reflecting main non-bonded interaction energies and expressing the structural disparities among different isomers, and greatly reducing parameters.