Group Additivity Determination for Enthalpies of Formation of Carbenium Ions

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• 作者：Kathryn R. Bjorkman ; Chun-Yi Sung ; Eric Mondor ; Janine C. Cheng ; Deng-Yang Jan ; Linda J. Broadbelt
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：December 17, 2014
• 年：2014
• 卷：53
• 期：50
• 页码：19446-19452
• 全文大小：316K
• ISSN：1520-5045

文摘

Modeling of acid-catalyzed hydrocarbon conversion processes at the mechanistic level requires rate coefficients for a large number of reactions. The computational demand of finding activation energy barriers for each reaction is substantially reduced by employing structure鈥搑eactivity correlations such as the Evans鈥揚olanyi relationship that correlates activation energy with the enthalpy of reaction. However, there are many species for which the enthalpies of formation are unknown. Therefore, group additivity methods to specify enthalpies of formation for each species involved in the reaction network are valuable. Quantum mechanical (QM) calculations and isodesmic reactions were used to calculate enthalpies of formation for a number of acyclic and cyclic carbenium ions, including allylic carbenium ions. These values compare favorably with experimental values, establishing Gaussian-4 as an accurate QM method for these calculations. Using these values, Benson-type group additivity values for enthalpies of formation were then derived through multiple linear regression. Enthalpies of formation values calculated from the group additivity scheme capture experimental and QM enthalpies of formation well and enhance the range of species that can be described by the group additivity approach.