Relationships between aqueous acidities and comput

Authors: Yuguang Ma Kevin C Gross Chad A Hollingsworth Paul G Seybold Jane S Murray

Publish Date: 2004/05/19

Volume: 10, Issue: 4, Pages: 235-239

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Abstract

Electrostatic potentials and average local ionization energies on the molecular surfaces of 19 phenols 17 benzoic acids and their respective conjugate bases were computed at the HF/STO5Gd//B3LYP/6311Gdp level Good correlations were found between pKas and the VSmax values of the neutral acids and the VSmin and barI textSmin of the conjugate bases for both sets of molecules VSmax is the most positive value of the electrostatic potential on the molecular surface and is an indicator of the ease with which the phenols and benzoic acids lose their acidic hydrogens VSmin and barI textSmin are the minimum values of the electrostatic potential and the local ionization energy computed on the molecular surface the VSmin and barI textSmin of the conjugate bases of the phenoxides and benzoates are indicative respectively of the tendencies of electrophiles to approach the anions VSmin and to react with the anions barI textSmin to reform the original acids The correlations observed between the computed molecular surface quantities taken as single parameters and the experimental pKa values ranged from R=0938 to R=0970 for the two classes of compounds

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