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ISSN: 1430-4171 (electronic version)

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Abstract Volume 8 Issue 1 (2003) pp 56-59

Determination of the Acid Dissociation Constant of Fluorescein and Its Derivatives through Visible Absorption Techniques

Timothy R. Brewer* and Mace R. Mattieson

Chemistry Department, Eastern Michigan University, Ypsilanti, MI 48197, Timothy.Brewer@emich.edu
Received May 7, 2002. Accepted August 5, 2002

Published online: 21 November 2002

Abstract. A discovery-based chemistry laboratory is presented that investigates the effects of electronegative substituents on the acid dissociation constants of fluorescein derivatives. The acid dissociation constants were measured through visible absorbance changes of the compounds at various pH values. The effect of electron-withdrawing constituents, such as chloro- and bromo-substituted fluorescein, is to lower the pK_a value relative to the parent fluorescent molecule. Molecular modeling using Hartree–Fock calculations was used to qualitatively support the experimental results.

Key Words:  Laboratories and Demonstrations; physical chemistry; instrumental analysis; computational chemistry

(*) Corresponding author. (E-mail: Timothy.Brewer@emich.edu)

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Issue date: February 1, 2003

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