Friday, 15 July 2005 - 2:20 PM

This presentation is part of: Inorganic Chemistry

Strength of Mononuclear Oxoacids

Dhia A. Habboush, Elizabeth A. Dumas, and Diane M. Marques. Sacred Heart University, Fairfield, CT

The simplest of the ternary oxoacids, mononuclear oxoacids contain hydroxyl group(s) (-OH) and oxo group(s) (=O) attached to a central heteroatom conforming to the general formula HmXOn. These compounds are acidic when X is a nonmetal or a metalloid and vary widely in strength, from a very weak H2CO3 and HClO to a very strong HClO4. Several factors, number of H atoms (m), number of O atoms (n), and electronegativity or formal charge of the central (X) influence the strength of oxoacids. Relating these factors to trends in acidity held well qualitatively for all oxoacids. Attempts to estimate actual pKa values with reasonable accuracy lead only to limited success. Via MS-Excel, a compilation of literature values were made in order to prepare various comparisons among the previously stated factors. Regression equations for the relationships between the pKa values and given factors, m, n, and electronegativity, were evaluated to determine correlation. Four empirical equations relating the strength of a given mononuclear oxoacid to its respective m, n, and electronegativity values were derived and related to the position of a given X and trends in the periodic table.

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