Theoretical determination of aqueous acid–base pm class="a-plus-plus">Km> values: electronic structure calculations and steered molecular dynamic simulations

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• 作者：S. Tolosa ; J. A. Sansón ; A. Hidalgo ; N. Mora-Diez
• 关键词：Aqueous pK calculations ; Acid–base equilibria ; SMD simulations ; M06 ; 2X ; MP2
• 刊名：Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta)
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：135
• 期：11
• 全文大小：680 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Theoretical and Computational Chemistry
  Inorganic Chemistry
  Organic Chemistry
  Physical Chemistry
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-2234
• 卷排序：135

文摘

The equilibrium constant (K) of several acid–base equilibria involving isomers of acetohydroxamic acid in aqueous solution is studied from a theoretical point of view applying electronic structure methods (at the M06-2X-SMD/6-311++G(d,p) and MP2-PCM/6-311++G(d,p) levels of theory) and steered molecular dynamic (SMD) simulations. The similarity of the results obtained indicates that SMD simulations can be successfully used to evaluate Gibbs energy changes in acid–base reactions in solution and pK values since these properties are in agreement with those found with quantum calculation and thermodynamic cycles. In the process of proton transfer from the imide isomers (the ZI and EI structures) toward the anion Z-amide, the deprotonation of the ZI(COH) molecule is the most favorable process kinetically and thermodynamically. It is observed that pK values are slightly higher for E-isomers and, particularly, for the deprotonation from the oxime group EI(NOH). Finally, we must emphasize the goodness of SMD simulations in solution to calculate this property as an alternative to using continuum solvation methods.